Venlafaxine Hcl

Drug overview for VENLAFAXINE HCL (venlafaxine hcl):

Generic name: VENLAFAXINE HCL (ven-luh-FAX-een)
Drug class: Antidepressants
Therapeutic class: Central Nervous System Agents

Venlafaxine, a selective serotonin- and norepinephrine-reuptake inhibitor (SNRI), is a phenylethylamine-derivative antidepressant and anxiolytic agent.

Venlafaxine is commercially available in the US as venlafaxine hydrochloride and as venlafaxine besylate. Venlafaxine hydrochloride conventional tablets are used in adults for the treatment of major depressive disorder. Venlafaxine hydrochloride extended-release capsules are used in adults for the treatment of major depressive disorder, generalized anxiety disorder, social anxiety disorder, and panic disorder.

Venlafaxine hydrochloride extended-release tablets are used in adults for the treatment of major depressive disorder and social anxiety disorder. Venlafaxine besylate extended-release tablets are used in adults for the treatment of major depressive disorder and generalized anxiety disorder.

DRUG IMAGES

VENLAFAXINE HCL 37.5 MG TABLET
VENLAFAXINE HCL 75 MG TABLET
VENLAFAXINE HCL 100 MG TABLET
VENLAFAXINE HCL 25 MG TABLET
VENLAFAXINE HCL 50 MG TABLET

The following indications for VENLAFAXINE HCL (venlafaxine hcl) have been approved by the FDA:

Indications:
Major depressive disorder

Professional Synonyms:
Major unipolar illness
Unipolar mood disorder

The following dosing information is available for VENLAFAXINE HCL (venlafaxine hcl):

Dosing
Administration
VENLAFAXINE HCL
VENLAFAXINE HCL

Dosages of venlafaxine hydrochloride and venlafaxine besylate are expressed in terms of venlafaxine.

Venlafaxine hydrochloride and venlafaxine besylate are administered orally. Venlafaxine hydrochloride conventional tablets are administered in divided doses 2 or 3 times a day with food. Venlafaxine hydrochloride extended-release capsules and tablets and venlafaxine besylate extended-release tablets are administered once daily, either in the morning or in the evening at approximately the same time each day, with food.

Food does not appear to affect GI absorption of venlafaxine hydrochloride. Ingestion of a high-fat meal when taken with venlafaxine besylate extended-release tablets increases plasma concentrations of venlafaxine and its metabolite. The extended-release capsules and tablets of venlafaxine hydrochloride and venlafaxine besylate tablets should be swallowed whole with fluid and should not be divided, crushed, chewed, or placed in water.

The entire contents of venlafaxine hydrochloride extended-release capsules may be sprinkled on a small amount of applesauce immediately prior to administration; the patient should drink some water after swallowing the entire mixture without chewing to ensure that the pellets are completely swallowed. Store venlafaxine hydrochloride conventional tablets, venlafaxine hydrochloride extended-release capsules, venlafaxine hydrochloride extended-release tablets, and venlafaxine besylate extended-release tablets at 20-25degreesC. Excursions are permitted between 15-30degreesC for venlafaxine hydrochloride extended-release tablets and venlafaxine besylate extended-release tablets.

Protect venlafaxine hydrochloride extended-release tablets from moisture and humidity. Keep venlafaxine hydrochloride conventional tablets dry.

Dosing information for VENLAFAXINE HCL
DRUG LABEL	DOSING TYPE	DOSING INSTRUCTIONS
VENLAFAXINE HCL 25 MG TABLET	Maintenance	Adults take 1 tablet (25 mg) by oral route 3 times per day with food
VENLAFAXINE HCL 37.5 MG TABLET	Maintenance	Adults take 1 tablet (37.5 mg) by oral route 2 times per day with food
VENLAFAXINE HCL 50 MG TABLET	Maintenance	Adults take 1 tablet (50 mg) by oral route 2 times per day with food
VENLAFAXINE HCL 75 MG TABLET	Maintenance	Adults take 1 tablet (75 mg) by oral route 2 times per day with food
VENLAFAXINE HCL 100 MG TABLET	Maintenance	Adults take 1 tablet (100 mg) by oral route 2 times per day with food

Generic dosing information for VENLAFAXINE HCL
DRUG LABEL	DOSING TYPE	DOSING INSTRUCTIONS
VENLAFAXINE HCL 25 MG TABLET	Maintenance	Adults take 1 tablet (25 mg) by oral route 3 times per day with food
VENLAFAXINE HCL 37.5 MG TABLET	Maintenance	Adults take 1 tablet (37.5 mg) by oral route 2 times per day with food
VENLAFAXINE HCL 50 MG TABLET	Maintenance	Adults take 1 tablet (50 mg) by oral route 2 times per day with food
VENLAFAXINE HCL 75 MG TABLET	Maintenance	Adults take 1 tablet (75 mg) by oral route 2 times per day with food
VENLAFAXINE HCL 100 MG TABLET	Maintenance	Adults take 1 tablet (100 mg) by oral route 2 times per day with food

The following drug interaction information is available for VENLAFAXINE HCL (venlafaxine hcl):

Contraindicated
Severe
Moderate

There are 2 contraindications. These drug combinations generally should not be dispensed or administered to the same patient. A manufacturer label warning that indicates the contraindication warrants inclusion of a drug combination in this category, regardless of clinical evidence or lack of clinical evidence to support the contraindication.

Drug Interaction	Drug Names
Serotonin Reuptake Inhibitors; SNRIs/Selected MAOIs SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient. MECHANISM OF ACTION: Serotonin reuptake inhibitors and MAOIs may act synergistically to increase blood pressure and evoke behavioral excitation. CLINICAL EFFECTS: Concurrent use or switching between agents without a sufficient washout period may result in serotonin syndrome. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity. PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The manufacturers of the selective serotonin reuptake inhibitors, the selective serotonin and norepinephrine reuptake inhibitors, nefazodone, and venlafaxine state that concurrent use with MAOIs is contraindicated. A minimum 5 week washout period should separate the switch of fluoxetine to a MAOI. A washout period of at least 21 days is recommended for the switch from vortioxetine to a MAOI. A washout period of at least 2 weeks is recommended for the switch of citalopram, escitalopram, fluvoxamine, paroxetine, sertraline, or vilazodone to a MAOI. A washout period of 7 days is recommended for the switch of dapoxetine, levomilnacipran, nefazodone, desvenlafaxine, and venlafaxine to a MAOI. A washout period of 5 days is recommended for the switch of duloxetine or milnacipran to a MAOI. Prior to starting any selective serotonin reuptake inhibitor, non-selective serotonin reuptake inhibitor, or duloxetine, allow a 2 week washout period after stopping MAOI therapy. These washout recommendations apply to the selective MAO-B inhibitors rasagiline and selegiline as well. If rasagiline is used in combination with fluvoxamine, patients should receive no more than 0.5mg of rasagiline daily. In emergency situations in patients maintained on SSRIs or SNRIs, weigh the availability and safety of alternatives to linezolid and methylene blue against the risk of serotonin syndrome. If linezolid or methylene blue therapy is required, the patient's SSRI or SNRI should be immediately discontinued. Patients should be monitored for serotonin syndrome for 2 weeks (5 weeks in the case of fluoxetine, 21 days in the case of vortioxetine, and 5 days in the case of duloxetine and milnacipran) or until 24 hours after the last dose of linezolid or methylene blue, whichever comes first. In non-emergency situations in patients maintained on SSRIs or SNRIs when linezolid or methylene blue therapy is planned, discontinue the patient's SSRI or SNRI at least 2 weeks (5 weeks in the case of fluoxetine, 21 days in the case of vortioxetine, and 5 days in the case of duloxetine and milnacipran) in advance of linezolid or methylene blue therapy. The patient's SSRI or SNRI therapy may be resumed 24 hours after the last dose of linezolid or methylene blue. Do not initiate SSRI or SNRI therapy in patients receiving linezolid or methylene blue until 24 hours after the last dose of these agents. DISCUSSION: This serious interaction (serotonin syndrome) has been reported with fluoxetine, sertraline, and venlafaxine. Although this has been not been reported with the fluvoxamine, nefazodone, or paroxetine, current recommendations by their manufacturers indicate that the potential for this interaction should be assumed. Manufacturer's product information for fluoxetine, paroxetine, and venlafaxine state that concurrent administration of these agents with a MAOI is contraindicated. The other selective serotonin reuptake inhibitors and non-selective serotonin reuptake inhibitors have shorter half-lives than fluoxetine. Therefore, the time frame during which the interaction would be expected to occur with agents and MAOIs would not be expected to be as prolonged as with fluoxetine. Furazolidone is also known to be a monoamine oxidase inhibitor. In a case report, a patient had stopped taking paroxetine 10 days prior to initiating St. John's wort. The evening after initiating St. John's wort, the patient took a paroxetine. At noon the next day, the patient was able to be awakened, but was incoherent, groggy, slow-moving, and almost unable to get up. Two hours later during an examination, she was groggy and lethargic, but able to respond appropriately. She complained of nausea, weakness, and fatigue. Her vital signs and physical exam were normal, except for a slow response time and limp muscle tone. She did not take any additional paroxetine and was normal the next day. The metabolism of rasagiline has been shown to be inhibited by CYP P-450-1A2 inhibitors such as fluvoxamine. Methylene blue, when administered intravenously, has been shown to reach sufficient concentrations to be a potent inhibitor of MAO-A. Serotonin syndrome has been reported following administration of methylene blue in patients receiving selective serotonin reuptake inhibitors (SSRIs). Metaxalone is a weak inhibitor of MAO. The FDA AERS contains reports of serotonin syndrome with the concurrent use of linezolid and citalopram, desvenlafaxine, duloxetine, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, and venlafaxine as well as reports of serotonin syndrome with concurrent injectable methylene blue and citalopram, clomipramine, escitalopram, desvenlafaxine, duloxetine, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, and venlafaxine. One or more of the drug pairs linked to this monograph have been included in a list of interactions that should be considered "high-priority" for inclusion and should not be inactivated in EHR systems. This DDI subset was vetted by an expert panel commissioned by the U.S. Office of the National Coordinator (ONC) for Health Information Technology.	AZILECT, EMSAM, FURAZOLIDONE, MARPLAN, MATULANE, METAXALONE, METHYLENE BLUE, NARDIL, PARNATE, PHENELZINE SULFATE, PROCARBAZINE HCL, PROVAYBLUE, RASAGILINE MESYLATE, SELEGILINE HCL, TRANYLCYPROMINE SULFATE, XADAGO, ZELAPAR
Selected CYP2D6 Substrates/Mavorixafor SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient. MECHANISM OF ACTION: Mavorixafor is a strong inhibitor of CYP2D6 and is expected to inhibit the metabolism of agents through this pathway.(1) CLINICAL EFFECTS: Concurrent use of mavorixafor may result in elevated levels of and toxicity from agents metabolized by CYP2D6.(1) PREDISPOSING FACTORS: With tricyclic antidepressants, the risk of seizures may be increased in patients with a history of head trauma or prior seizure; CNS tumor; severe hepatic cirrhosis; excessive use of alcohol or sedatives; addiction to opiates, cocaine, or stimulants; use of over-the-counter stimulants and anorectics; diabetics treated with oral hypoglycemics or insulin; or with concomitant medications known to lower seizure threshold (antipsychotics, theophylline, systemic steroids). With anticholinergic agents, the risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(2) PATIENT MANAGEMENT: The US manufacturer of mavorixafor states concurrent use with CYP2D6 substrate that are highly dependent on CYP2D6 metabolism is contraindicated.(1) The US manufacturer of doxepin states if concurrent use of doxepin and strong CYP2D6 inhibitors such as mavorixafor is warranted, monitor doxepin plasma concentrations and reduce the doxepin dose based on doxepin plasma concentrations.(5) DISCUSSION: Mavorixafor (400 mg) increased dextromethorphan (CYP2D6 substrate) maximum concentration (Cmax) and area-under-curve (AUC) by 6-fold and 9-fold, respectively.(1) Selected CYP2D6 substrates linked to this monograph include: aripiprazole, brexpiprazole, desipramine, deutetrabenazine, dextromethorphan, doxepin, encainide, fenfluramine, metoclopramide, methoxyphenamine, metoprolol, mexiletine, nebivolol, paroxetine, perphenazine, risperidone, tetrabenazine, trimipramine, venlafaxine, and yohimbine.	XOLREMDI

Drug Interaction

Drug Names

Serotonin Reuptake Inhibitors; SNRIs/Selected MAOIs

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Serotonin reuptake inhibitors and MAOIs may act synergistically to increase blood pressure and evoke behavioral excitation.

CLINICAL EFFECTS: Concurrent use or switching between agents without a sufficient washout period may result in serotonin syndrome. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturers of the selective serotonin reuptake inhibitors, the selective serotonin and norepinephrine reuptake inhibitors, nefazodone, and venlafaxine state that concurrent use with MAOIs is contraindicated. A minimum 5 week washout period should separate the switch of fluoxetine to a MAOI. A washout period of at least 21 days is recommended for the switch from vortioxetine to a MAOI.

A washout period of at least 2 weeks is recommended for the switch of citalopram, escitalopram, fluvoxamine, paroxetine, sertraline, or vilazodone to a MAOI. A washout period of 7 days is recommended for the switch of dapoxetine, levomilnacipran, nefazodone, desvenlafaxine, and venlafaxine to a MAOI. A washout period of 5 days is recommended for the switch of duloxetine or milnacipran to a MAOI.

Prior to starting any selective serotonin reuptake inhibitor, non-selective serotonin reuptake inhibitor, or duloxetine, allow a 2 week washout period after stopping MAOI therapy. These washout recommendations apply to the selective MAO-B inhibitors rasagiline and selegiline as well. If rasagiline is used in combination with fluvoxamine, patients should receive no more than 0.5mg

of rasagiline daily. In emergency situations in patients maintained on SSRIs or SNRIs, weigh the availability and safety of alternatives to linezolid and methylene blue against the risk of serotonin syndrome. If linezolid or methylene blue therapy is required, the patient's SSRI or SNRI should be immediately discontinued.

Patients should be monitored for serotonin syndrome for 2 weeks (5 weeks in the case of fluoxetine, 21 days in the case of vortioxetine, and 5 days in the case of duloxetine and milnacipran) or until 24 hours after the last dose of linezolid or methylene blue, whichever comes first. In non-emergency situations in patients maintained on SSRIs or SNRIs when linezolid or methylene blue therapy is planned, discontinue the patient's SSRI or SNRI at least 2 weeks (5 weeks in the case of fluoxetine, 21 days in the case of vortioxetine, and 5 days in the case of duloxetine and milnacipran) in advance of linezolid or methylene blue therapy. The patient's SSRI or SNRI therapy may be resumed 24 hours after the last dose of linezolid or methylene blue. Do not initiate SSRI or SNRI therapy in patients receiving linezolid or methylene blue until 24 hours after the last dose of these agents.

DISCUSSION: This serious interaction (serotonin syndrome) has been reported with fluoxetine, sertraline, and venlafaxine. Although this has been not been reported with the fluvoxamine, nefazodone, or paroxetine, current recommendations by their manufacturers indicate that the potential for this interaction should be assumed. Manufacturer's product information for fluoxetine, paroxetine, and venlafaxine state that concurrent administration of these agents with a MAOI is contraindicated.

The other selective serotonin reuptake inhibitors and non-selective serotonin reuptake inhibitors have shorter half-lives than fluoxetine. Therefore, the time frame during which the interaction would be expected to occur with agents and MAOIs would not be expected to be as prolonged as with fluoxetine. Furazolidone is also known to be a monoamine oxidase inhibitor.

In a case report, a patient had stopped taking paroxetine 10 days prior to initiating St. John's wort. The evening after initiating St.

John's wort, the patient took a paroxetine. At noon the next day, the patient was able to be awakened, but was incoherent, groggy, slow-moving, and almost unable to get up. Two hours later during an examination, she was groggy and lethargic, but able to respond appropriately.

She complained of nausea, weakness, and fatigue. Her vital signs and physical exam were normal, except for a slow response time and limp muscle tone. She did not take any additional paroxetine and was normal the next day.

The metabolism of rasagiline has been shown to be inhibited by CYP P-450-1A2 inhibitors such as fluvoxamine. Methylene blue, when administered intravenously, has been shown to reach sufficient concentrations to be a potent inhibitor of MAO-A. Serotonin syndrome has been reported following administration of methylene blue in patients receiving selective serotonin reuptake inhibitors (SSRIs).

Metaxalone is a weak inhibitor of MAO. The FDA AERS contains reports of serotonin syndrome with the concurrent use of linezolid and citalopram, desvenlafaxine, duloxetine, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, and venlafaxine as well as reports of serotonin syndrome with concurrent injectable methylene blue and citalopram, clomipramine, escitalopram, desvenlafaxine, duloxetine, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, and venlafaxine. One or more of the drug pairs linked to this monograph have been included in a list of interactions that should be considered "high-priority" for inclusion and should not be inactivated in EHR systems.

This DDI subset was vetted by an expert panel commissioned by the U.S. Office of the National Coordinator (ONC) for Health Information Technology.

AZILECT, EMSAM, FURAZOLIDONE, MARPLAN, MATULANE, METAXALONE, METHYLENE BLUE, NARDIL, PARNATE, PHENELZINE SULFATE, PROCARBAZINE HCL, PROVAYBLUE, RASAGILINE MESYLATE, SELEGILINE HCL, TRANYLCYPROMINE SULFATE, XADAGO, ZELAPAR

Selected CYP2D6 Substrates/Mavorixafor

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Mavorixafor is a strong inhibitor of CYP2D6 and is expected to inhibit the metabolism of agents through this pathway.(1)

CLINICAL EFFECTS: Concurrent use of mavorixafor may result in elevated levels of and toxicity from agents metabolized by CYP2D6.(1)

PREDISPOSING FACTORS: With tricyclic antidepressants, the risk of seizures may be increased in patients with a history of head trauma or prior seizure; CNS tumor; severe hepatic cirrhosis; excessive use of alcohol or sedatives; addiction to opiates, cocaine, or stimulants; use of over-the-counter stimulants and anorectics; diabetics treated with oral hypoglycemics or insulin; or with concomitant medications known to lower seizure threshold (antipsychotics, theophylline, systemic steroids). With anticholinergic agents, the risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(2)

PATIENT MANAGEMENT: The US manufacturer of mavorixafor states concurrent use with CYP2D6 substrate that are highly dependent on CYP2D6 metabolism is contraindicated.(1) The US manufacturer of doxepin states if concurrent use of doxepin and strong CYP2D6 inhibitors such as mavorixafor is warranted, monitor doxepin plasma concentrations and reduce the doxepin dose based on doxepin plasma concentrations.(5)

DISCUSSION: Mavorixafor (400 mg) increased dextromethorphan (CYP2D6 substrate) maximum concentration (Cmax) and area-under-curve (AUC) by 6-fold and 9-fold, respectively.(1) Selected CYP2D6 substrates linked to this monograph include: aripiprazole, brexpiprazole, desipramine, deutetrabenazine, dextromethorphan, doxepin, encainide, fenfluramine, metoclopramide, methoxyphenamine, metoprolol, mexiletine, nebivolol, paroxetine, perphenazine, risperidone, tetrabenazine, trimipramine, venlafaxine, and yohimbine.

XOLREMDI

There are 7 severe interactions. These drug interactions can produce serious consequences in most patients. Actions required for severe interactions include, but are not limited to, discontinuing one or both agents, adjusting dosage, altering administration scheduling, and providing additional patient monitoring. Review the full interaction monograph for more information.

Drug Interaction	Drug Names
Selected Anticoagulants (Vitamin K antagonists)/SSRIs; SNRIs SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction. MECHANISM OF ACTION: SSRI or SNRI inhibition of platelet serotonin uptake may result in impaired platelet aggregation.(1-11) This effect may be additive or synergistic when combined with other agents which impair hemostasis. Fluvoxamine is an inhibitor of CYP2C9 mediated metabolism of warfarin.(9) CLINICAL EFFECTS: Concurrent use of selected anticoagulants and SSRIs or SNRIs may increase the risk for bleeding. PREDISPOSING FACTORS: The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Renal impairment has been associated with an elevated risk of GI bleed in patients on SSRIs.(11) Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs). PATIENT MANAGEMENT: For the combination of fluvoxamine and warfarin: when possible change to a SSRI which does not inhibit warfarin metabolism (e.g. citalopram or paroxetine). For patients who require this combination, monitor for an increase in INR when fluvoxamine is started or the dose is increased. The warfarin dose may need to be reduced. For all anticoagulant/SSRI or SNRI combinations, if concurrent therapy is warranted, monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin and/or hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. When applicable, perform agent-specific laboratory test (e.g. INR, aPTT) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. The time of highest risk for a coumarin-type drug interaction is when the precipitant drug is initiated or discontinued. Contact the prescriber before initiating, altering the dose or discontinuing either drug. DISCUSSION: The manufacturer's product information for fluvoxamine reports a study in which the plasma warfarin concentrations increased 98% and prothrombin times were prolonged in patients who received concurrent fluvoxamine and warfarin.(9) In a single study in 24 healthy patients, concurrent administration of paroxetine and warfarin resulted in clinically significant bleeding in five patients. No changes in paroxetine or warfarin disposition were seen.(13) In a review describing the bleeding risk with SRIs, warfarin was associated with an increased rate of hemorrhage among SRI users (adjusted relative risk = 1.41).(14) In a cohort study of patients taking warfarin in combination with an SSRI versus warfarin treatment alone, an analysis including first bleedings revealed a hazard ratio of 3.49 for bleeding during treatment with a combination of SSRI and warfarin compared with warfarin only.(15) A retrospective study of warfarin-treated patients prescribed or not prescribed an antidepressant showed that use of an SSRI with warfarin was significantly associated with increased risk of any bleed (overall risk (OR)=2.6), major bleeding (OR=4.4), and hospitalization secondary to bleeding (OR=7.0) as compared to those not taking an SSRI.(16) A population based study of patient outcomes in 176 primary intracerebral hemorrhage patients showed that 19 patients taking SSRI/SNRIs together with warfarin had an increased 30-day case fatality rate of 78.9% compared to warfarin alone (50.7%).(17) In a study of the Anticoagulation and Risk factors in Atrial fibrillation (ATRIA) cohort, hemorrhage rates were higher during periods of SSRI exposure compared with periods on no antidepressants (2.32 per 100 person-years vs 1.35 per 100 person-years). After adjusting for bleeding risk and time in INR range > 3, SSRI exposure was associated with an increased rate of hemorrhage compared with no antidepressants (adjusted relative risk = 1.41).(18) Increased bleeding risk has been found when patients receive 3 agents which can affect bleeding risk: an anticoagulant, SSRI and NSAID.(19) In a retrospective review of 5 years of data from the Pharmaco-Epidemiologic Prescription Database, hospitalizations for upper gastro-intestinal bleeding in antidepressant users were compared to those in non-antidepressant users. The risk of a bleed in a patient using an NSAID only based on an observed-expected ratio was 4.5 and in a patient using low-dose aspirin only was 2.5. Concurrent use of a SSRI with NSAIDs or low-dose aspirin increased the risk of bleeding to 12.2 and 5.2, respectively.(19) In another study, there were 16 cases of upper gastrointestinal bleeding in patients receiving concurrent therapy with SSRIs and NSAIDs. Adjusted relative risk of bleeding with NSAIDs, SSRIs, or both were 3.7, 2.6, or 15.6, respectively.(20) A large systematic review was performed on 72 warfarin drug-drug interactions studies that reported on bleeding, thromboembolic events, or death. Most studies were retrospective cohorts. A meta-analysis of 10 of those studies found a higher rate of clinically significant bleeding in patients on warfarin and antidepressants (OR=1.54; 95% CI 1.4-1.7). Increased bleeding risk was also seen in subgroup analyses with SSRIs (OR=1.62; 95% CI 1.42-1.85) but not SNRIs. There was an increased case fatality rate for intracerebral hemorrhage with SSRIs and SNRIs (OR=3.64; 95% CI 1.15-11.53).(21) There are two published case reports involving increased effects of warfarin following addition of fluoxetine. Another case report is inconclusive. In a study in seven healthy volunteers, neither single dose or eight days of consecutive therapy resulted in alteration of warfarin clearance.(22, 23) In a parallel group study involving 12 healthy volunteers, the prothrombin time and area-under-curve (AUC) were increased and the normalization of prothrombin time was decreased with concurrent warfarin and sertraline. There was also a clinically insignificant increase in warfarin protein binding.(24) There is one case report of increased INR during concurrent warfarin and duloxetine.(25)	ANISINDIONE, JANTOVEN, WARFARIN SODIUM
Serotonin Reuptake Inhibitors/Linezolid SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction. MECHANISM OF ACTION: Serotonin reuptake inhibitors and linezolid, which inhibits MAO, may act synergistically to increase central nervous system (CNS) serotonin concentrations, leading to toxicity. CLINICAL EFFECTS: Concurrent use or switching between agents without a sufficient washout period may result in serotonin syndrome. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity.(2) Serotonin syndrome may result in death. PREDISPOSING FACTORS: High doses of serotonin reuptake inhibitors or concurrent use of multiple drugs which increase CNS serotonin levels may increase risk for serotonin syndrome. PATIENT MANAGEMENT: If linezolid is required for urgent or life threatening treatment, the FDA states the interacting serotonergic drug should be stopped. Although discontinued, serotonin toxicity due to the interaction is still possible. Patients should be monitored for CNS serotonin toxicity for two weeks (five weeks if fluoxetine, 3 weeks if vortioxetine, 7 days if desvenlafaxine or venlafaxine, or 5 days if duloxetine was taken) or until 24 hours after the last linezolid dose, whichever comes first. Therapy with the SSRI may be resumed 24 hours after the last dose of linezolid.(1,3-13) DISCUSSION: Serotonin syndrome has been reported in four patients receiving concurrent citalopram and linezolid, in a patient in whom linezolid was initiated 18 days after fluoxetine discontinuation, in a patient receiving concurrent linezolid and fluoxetine, in a patient in whom linezolid was initiated three days after the discontinuation of paroxetine, in three patients receiving concurrent linezolid and sertraline, and in a patient receiving concurrent linezolid and venlafaxine. Many authors state that linezolid is a weak MAOI and rarely causes serotonin toxicity. Cases of serotonin toxicity were rapidly reversible with discontinuation of the offending agent(s) and supportive care. Some authors suggest that use of serotonergic medications should not preclude the use of linezolid but that the clinical situation should be assessed. If concurrent use or use of linezolid without a washout is warranted, the patient should be closely monitored.(24-29)	LINEZOLID, LINEZOLID-0.9% NACL, LINEZOLID-D5W, ZYVOX
Metoclopramide/SSRIs; SNRIs SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction. MECHANISM OF ACTION: Both metoclopramide and serotonin reuptake inhibitors (SSRIs, SNRIs) may be associated with extrapyramidal side effects (EPS).(1-7) Some SSRIs or SNRIs may also inhibit the metabolism of metoclopramide by CYP2D6, further increasing the risk for EPS.(8) A few case reports have reported serotonin syndrome with this combination.(9,10) The mechanism of action is not clear. CLINICAL EFFECTS: Concurrent use may result in extrapyramidal side effects (EPS) such as acute dystonia, Parkinsonism, akathisia, neuroleptic malignant syndrome, or tardive dyskinesia. Tardive dyskinesia may be permanent. Serotonin syndrome has been reported infrequently with this combination. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity. Adverse effects may be may be more frequent or severe with SSRIs or SNRIs which inhibit CYP2D6 mediated metabolism of metoclopramide. CYP2D6 inhibitors linked to this monograph and their strength of inhibition(8) (S=strong, M=moderate, W=weak) are: fluoxetine(S), paroxetine(S), duloxetine(M), desvenlafaxine(W), fluvoxamine(W), sertraline(W), escitalopram(W), and venlafaxine(magnitude unclear). Agents linked to this monograph which are not known to inhibit CYP2D6 are levomilnacipran, milnacipran, and vilazodone. PREDISPOSING FACTORS: Patients with renal and/or hepatic impairment may have an increased risk from this combination. The risk of extrapyramidal symptoms is also increased in patients on metoclopramide for longer than 12 weeks. Elderly patients, especially elderly women, and diabetics are at higher risk of developing tardive dyskinesia. Other extrapyramidal symptoms, like acute dystonia, have occurred more frequently in patients younger than 30 years old.(1) PATIENT MANAGEMENT: If possible, consider alternatives to metoclopramide in patients receiving SSRI or SNRI therapy. If concurrent therapy is warranted, monitor patients for signs of extrapyramidal side effects (acute dystonic reaction, Parkinsonian symptoms, akathisia, tardive dyskinesia) and neuroleptic malignant syndrome. Symptoms unique to serotonin syndrome may include diaphoresis, hyperreflexia, and clonus.(11) The manufacturer of metoclopramide says to avoid treatment with metoclopramide for longer than 12 weeks, and to use the lowest possible dose.(1) For gastroesophageal reflux, the manufacturer recommends reduction in the dosage of metoclopramide to 5 mg four times daily (thirty minutes before each meal and at bedtime) or 10 mg taken three times daily for a maximum daily dosage of 30 mg in patients taking fluoxetine or paroxetine.(1) For acute and recurrent diabetic gastroparesis, reduce the dosage of metoclopramide to 5 mg four times daily (30 minutes before each meal and at bedtime) for a maximum daily dosage of 20 mg in patients taking fluoxetine or paroxetine.(1) DISCUSSION: In a study in 20 healthy male subjects, concurrent fluoxetine (60 mg daily for 9 days to simulate steady-state levels of 20 mg daily) increased the maximum concentration (Cmax) and area-under-curve (AUC) of metoclopramide (20 mg single dose) by 42% and 89%, respectively.(2) There have been case reports of extrapyramidal side effects(EPS) in patients receiving concurrent metoclopramide and fluoxetine,(3) fluvoxamine,(4) sertraline,(5) and venlafaxine.(9) A review of a review of EPS associated with SSRIs or SNRIs, with or without other precipitating agents has been published.(6) Case reports have described serotonin syndrome with the combination of sertraline or venlafaxine with metoclopramide.(9,10)	GIMOTI, METOCLOPRAMIDE HCL, REGLAN
Meperidine/Clomipramine; Imipramine; SSRIs; SNRIs; SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction. MECHANISM OF ACTION: The concurrent administration of meperidine with a selective serotonin reuptake inhibitor or a serotonin/norepinephrine reuptake inhibitor (SNRI) may result in additive blockade of serotonin reuptake, resulting in central serotonergic hyperstimulation.(1,2) The combination of meperidine and selective serotonin reuptake inhibitors or SNRIs may also lower the seizure threshold. CLINICAL EFFECTS: Concurrent administration may result in serotonin syndrome. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity.(2) PREDISPOSING FACTORS: Predisposing factors include renal dysfunction and use of multiple agents which increase central serotonin levels. Chronic use of meperidine or high doses of SSRIs or SNRIs would also be expected to increase the risk for serotonin toxicity. PATIENT MANAGEMENT: Use an alternative analgesic whenever possible, particularly in patients with renal impairment. If concurrent therapy is warranted, patients should be monitored for signs and symptoms of serotonin syndrome, seizure activity. Instruct patients to report muscle twitching, tremors, shivering and stiffness, fever, heavy sweating, heart palpitations, restlessness, confusion, agitation, trouble with coordination, or severe diarrhea. DISCUSSION: Case reports describe the interaction between meperidine and serotonin-increasing agents.(3-5) Meperidine has long been associated with the risk for serotonin syndrome, particularly when used with monoamine oxidase inhibitors (MAOIs).(6) In addition to SSRIs and SNRIs, clomipramine, a tricyclic antidepressant(TCA) with strong serotonin effects and imipramine, a TCA with more moderate serotonin effects are also included in this monograph.(7)	DEMEROL, MEPERIDINE HCL, MEPERIDINE HCL-0.9% NACL
Iobenguane I 123/Agents that Affect Catecholamines SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction. MECHANISM OF ACTION: Many compounds that reduce catecholamine uptake or that deplete catecholamine stores may interfere with iobenguane uptake into cells.(1) CLINICAL EFFECTS: Compounds that reduce catecholamine uptake or that deplete catecholamine stores may interfere with imaging completed with iobenguane.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Discuss the use of agents that affect catecholamines. Discontinue drugs that reduce catecholamine uptake or deplete catecholamine stores prior to imaging with iobenguane. Before imaging with iobenguane, discontinue agents that affect catecholamines for at least 5 biological half-lives, as clinically tolerated.(1) DISCUSSION: Many agents may reduce catecholamine uptake or deplete catecholamine stores.(1) Examples include: - CNS stimulants or amphetamines (e.g. cocaine, methylphenidate, dextroamphetamine) - norepinephrine and dopamine reuptake inhibitors (e.g. phentermine) - norepinephrine and serotonin reuptake inhibitors (e.g. tramadol) - monoamine oxidase inhibitors (e.g. phenelzine, linezolid) - central monoamine depleting drugs (e.g. reserpine) - non-select beta adrenergic blocking drugs (e.g. labetalol) - alpha agonists or alpha/beta agonists (e.g. pseudoephedrine, phenylephrine, ephedrine, phenylpropanolamine, naphazoline) - tricyclic antidepressants or norepinephrine reuptake inhibitors (e.g. amitriptyline, bupropion, duloxetine, mirtazapine, venlafaxine) - botanicals that may inhibit reuptake of norepinephrine, serotonin or dopamine (e.g. ephedra, ma huang, St. John's Wort, yohimbine)	ADREVIEW
Selected CYP2D6 Substrates/Panobinostat SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction. MECHANISM OF ACTION: Panobinostat is a moderate inhibitor of CYP2D6 and is expected to inhibit the metabolism of agents through this pathway.(1) CLINICAL EFFECTS: Concurrent use of panobinostat may result in elevated levels of and toxicity from agents metabolized by CYP2D6.(1) PREDISPOSING FACTORS: With tricyclic antidepressants, the risk of seizures may be increased in patients with a history of head trauma or prior seizure; CNS tumor; severe hepatic cirrhosis; excessive use of alcohol or sedatives; addiction to opiates, cocaine, or stimulants; use of over-the-counter stimulants and anorectics; diabetics treated with oral hypoglycemics or insulin; or with concomitant medications known to lower seizure threshold (antipsychotics, theophylline, systemic steroids). With anticholinergic agents, the risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(4) PATIENT MANAGEMENT: Avoid the concurrent use of panobinostat with agents that are sensitive CYP2D6 or CYP2D6 substrates with a narrow therapeutic index. If concurrent use is warranted, monitor patients for toxicity.(1) DISCUSSION: In a study in 14 subjects with advanced cancer, panobinostat (20 mg daily on Days 3, 5, and 8) increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of dextromethorphan (60 mg) by 20-200% and 20-130%, respectively. Dextromethorphan exposures were extremely variable.(1) Selected CYP2D6 substrates linked to this monograph include: desipramine, deutetrabenazine, dextromethorphan, doxepin, encainide, methoxyphenamine, metoprolol, nebivolol, paroxetine, perphenazine, risperidone, tetrabenazine, trimipramine, venlafaxine, and yohimbine.	FARYDAK
Selected CYP1A2 or CYP2D6 Substrates/Givosiran SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction. MECHANISM OF ACTION: Givosiran interferes with the first and rate-limiting step in hepatic heme biosynthesis, which may lower hepatic heme levels and decrease production and/or activity of cytochrome P450 enzymes.(1,2) CLINICAL EFFECTS: Concurrent use of givosiran may result in elevated levels of and toxicity from agents metabolized by CYP1A2 or CYP2D6.(1) PREDISPOSING FACTORS: With tricyclic antidepressants, the risk of seizures may be increased in patients with a history of head trauma or prior seizure; CNS tumor; severe hepatic cirrhosis; excessive use of alcohol or sedatives; addiction to opiates, cocaine, or stimulants; use of over-the-counter stimulants and anorectics; diabetics treated with oral hypoglycemics or insulin; or with concomitant medications known to lower seizure threshold (antipsychotics, theophylline, systemic steroids). With anticholinergic agents, the risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(3) PATIENT MANAGEMENT: Avoid the concurrent use of givosiran with agents that are sensitive substrates of CYP1A2 or CYP2D6, or CYP1A2 or CYP2D6 substrates with a narrow therapeutic index. If concurrent use is unavoidable, decrease the dose of the CYP1A2 or CYP2D6 substrate and monitor patients for toxicity. DISCUSSION: A study of 9 patients with acute intermittent porphyria found that givosiran decreased the maximum concentration (Cmax) and area-under-curve (AUC) of caffeine (a CYP1A2 substrate) by 1.3- and 3.1-fold, respectively, compared to caffeine alone. Givosiran also decreased the Cmax and AUC of dextromethorphan (a CYP2D6 substrate) by 2- and 2.4-fold, respectively, compared to dextromethorphan alone.(1,2) Selected CYP2D6 substrates linked to this monograph include: desipramine, deutetrabenazine, dextromethorphan, doxepin, encainide, methoxyphenamine, metoprolol, nebivolol, nefazodone, paroxetine, perphenazine, risperidone, tetrabenazine, trimipramine, and venlafaxine. Selected CYP1A2 substrates linked to this monograph include: agomelatine, aminophylline, rasagiline, tacrine, theophylline, tizanidine, and yohimbine.	GIVLAARI

There are 20 moderate interactions. The clinician should assess the patient’s characteristics and take action as needed. Actions required for moderate interactions include, but are not limited to, discontinuing one or both agents, adjusting dosage, altering administration.

Drug Interaction	Drug Names
Dexfenfluramine; Fenfluramine/Serotoninergic Agents SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Concurrent administration may result in additive effects on serotonin, resulting in serotonin syndrome. CLINICAL EFFECTS: May result in serotonin syndrome, a potentially life-threatening syndrome which may include one or more of the following symptoms: tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity. PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The manufacturer of fenfluramine states that fenfluramine should be used with caution with other serotonergic agents such as the selective serotonin reuptake inhibitors, sumatriptan, or dihydroergotamine. If concurrent therapy is warranted, patients should be monitored for signs and symptoms of serotonin syndrome. Instruct patients to report muscle twitching, tremors, shivering and stiffness, fever, heavy sweating, heart palpitations, restlessness, confusion, agitation, trouble with coordination, or severe diarrhea. DISCUSSION: This interaction is based on FDA mandated class labeling for these agents. Although there is no clinical documentation for an interaction between dexfenfluramine or fenfluramine and either the selective serotonin reuptake inhibitors, sumatriptan, or dihydroergotamine, caution is still warranted. This syndrome has been reported with the selective serotonin reuptake inhibitors and other serotonergic agents, including sumatriptan and dihydroergotamine.	FINTEPLA
Tapentadol/SSRIs; SNRIs SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: The concurrent administration of tapentadol(1) with a selective serotonin reuptake inhibitor (SSRI) or a serotonin/norepinephrine reuptake inhibitor (SNRI) may result in additive blockade of serotonin reuptake, leading to central serotonergic hyperstimulation.(1) The combination of tapentadol and SSRIs or SNRIs may impact seizure control.(1) CLINICAL EFFECTS: Concurrent administration may increase the risk for serotonin syndrome. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity.(2) Concurrent administration may increase the risk for seizures, especially in susceptible individuals.(1) PREDISPOSING FACTORS: Treatment with multiple medications which increase serotonin levels or with medications which inhibit the metabolism of serotonin increasing drugs are risk factors for serotonin syndrome.(2) PATIENT MANAGEMENT: If concurrent therapy of tapentadol with a SSRI or SNRI is warranted, patients should be closely monitored for signs and symptoms of serotonin syndrome or increased seizure frequency. Tapentadol may need to be discontinued. DISCUSSION: Concurrent use of tapentadol with SSRIs or SNRIs may result in additive blockage of serotonin reuptake, leading to central serotonergic hyperstimulation. Cases of serotonin syndrome have been reported with tapentadol in combination with other serotonergic drugs.(1) Use of tapentadol has been associated with increased seizure frequency in patients with seizure disorders.(1) SSRIs and SNRIs linked to this monograph are: citalopram, desvenlafaxine, duloxetine, escitalopram, fluoxetine, fluvoxamine, milnacipran, paroxetine, sertraline, sibutramine, venlafaxine, vilazodone, and vortioxetine.	NUCYNTA, NUCYNTA ER
Amphetamines; Phentermine/SSRIs; SNRIs SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Amphetamines may affect serotonin release and/or reuptake, depending on their molecular structure. Ring substitution tends to increase amphetamine-induced release of endogenous serotonin. However, the effect on serotonin release may also be dose related and is more likely if the amphetamine is taken in doses greater than those approved and generally employed in treating Attention-deficit-hyperactivity-disorder, or if abused, especially over long periods of time.(1) Amphetamines, phentermine and serotonin-norepinephrine reuptake inhibitors(SNRIs) may have additive effects on blood pressure. CLINICAL EFFECTS: Concurrent use of amphetamines with agents that affect serotonin may increase the risk of serotonin syndrome. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity.(8) Concurrent use of amphetamines or phentermine and a SNRI may increase the risk for high blood pressure or make hypertension more difficult to control. SSRIs and SNRIs linked to this monograph are: citalopram, desvenlafaxine, duloxetine, escitalopram, fluoxetine, fluvoxamine, levomilnacipran, milnacipran, paroxetine, sertraline, venlafaxine, vilazodone and vortioxetine. PREDISPOSING FACTORS: High doses or long-term abuse of amphetamines may increase the risk of this interaction. PATIENT MANAGEMENT: The concurrent use of amphetamines with SSRIs or SNRIs should be approached with appropriate monitoring. Instruct patients receiving concurrent therapy to report any signs or symptoms of serotonin syndrome immediately. Monitor blood pressure during concurrent therapy and adjust dosage or change medication for persistent increases in blood pressure. If concurrent therapy is warranted, patients should be monitored for signs and symptoms of serotonin syndrome. Instruct patients to report muscle twitching, tremors, shivering and stiffness, fever, heavy sweating, heart palpitations, restlessness, confusion, agitation, trouble with coordination, or severe diarrhea. DISCUSSION: In a case report, a 13 year-old female experienced tachycardia when amphetamine was added to her sertraline regimen.(2) Increased side effects have also been reported in patients maintained on fluoxetine who ingested illicit amphetamines.(3) In a case report, a 22 year-old female had previously been taking phentermine and oral contraceptive agents. The patient stopped taking phentermine and, after an undetermined length of time, started taking fluoxetine (20 mg daily). The patient discontinued her fluoxetine after three months. Eight days later, she took one dose of phentermine (30 mg). Within several hours, she developed jitteriness, stomach cramps, dry eyes, palpitations, and tremors. The patient received once dose of lorazepam (1.5 mg) and her symptoms resolved over night.(4) In a case report, a 32 year-old male developed agitation, anxiety, shivering, tremors, and diaphoresis two weeks after adding venlafaxine to his dexamphetamine.(5) There have also been reports of safe and effective use of amphetamines with fluoxetine,(6) dextroamphetamine and sertraline,(6) and dextroamphetamine with fluoxetine.(7)	ADDERALL, ADDERALL XR, ADZENYS XR-ODT, AMPHETAMINE ER ODT, AMPHETAMINE SULFATE, DESOXYN, DEXEDRINE, DEXTROAMPHETAMINE SULFATE, DEXTROAMPHETAMINE SULFATE ER, DEXTROAMPHETAMINE-AMPHET ER, DEXTROAMPHETAMINE-AMPHETAMINE, DYANAVEL XR, EVEKEO, HYDROXYAMPHETAMINE HBR, LISDEXAMFETAMINE DIMESYLATE, LOMAIRA, METHAMPHETAMINE HCL, MYDAYIS, PHENTERMINE HCL, PHENTERMINE-TOPIRAMATE ER, PROCENTRA, QSYMIA, VYVANSE, XELSTRYM, ZENZEDI
SSRIs; SNRIs/Selected NSAIDs; Aspirin SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Serotonin release by platelets plays a role in hemostasis.(1,2) The increased risk of bleeding may be a result of a decrease in serotonin reuptake by platelets. CLINICAL EFFECTS: Concurrent use of a selective serotonin reuptake inhibitor(1-7,13) or a serotonin-norepinephrine reuptake inhibitor(8-10) and a NSAID may result in bleeding. PREDISPOSING FACTORS: The risk for bleeding episodes may be greater in patients with multiple disease-associated factors (e.g. thrombocytopenia, advanced liver disease). Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g., anticoagulants, antiplatelets, or corticosteroids. Risk of GI bleed may be increased in patients who are of older age, in poor health status, or who use alcohol or smoke. Risk may also be increased with longer duration of NSAID use and prior history of peptic ulcer disease and/or GI bleeding. Renal impairment has been associated with an elevated risk of GI bleed in patients on SSRIs.(15) PATIENT MANAGEMENT: Selective serotonin reuptake inhibitors(1-7,13) or serotonin-norepinephrine reuptake inhibitors(8-10) and NSAIDs should be used concurrently with caution. Patients should be warned about the increased risk of bleeding and be educated about signs and symptoms of bleeding.(1-11,13) If concurrent therapy is warranted, monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin, hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. Discontinue anti-platelet agents in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. DISCUSSION: In a retrospective review of 5 years of data from the Pharmaco-Epidemiologic Prescription Database, hospitalizations for upper gastro-intestinal bleeding in antidepressant users were compared to those in non-antidepressant users. The risk of a bleed in a patient using an NSAID only based on an observed-expected ratio was 4.5 and in a patient using low-dose aspirin only was 2.5. Concurrent use of a selective serotonin reuptake inhibitor with NSAIDs or low-dose aspirin increased the risk of bleeding to 12.2 and 5.2, respectively.(11) In another study, there were 16 cases of upper gastrointestinal bleeding in patients receiving concurrent therapy with selective serotonin reuptake inhibitors and NSAIDs. Adjusted relative risk of bleeding with NSAIDs, selective serotonin reuptake inhibitors, or both were 3.7, 2.6, or 15.6, respectively.(12)	ACETYL SALICYLIC ACID, ANAPROX DS, ARTHROTEC 50, ARTHROTEC 75, ASA-BUTALB-CAFFEINE-CODEINE, ASCOMP WITH CODEINE, ASPIRIN, ASPIRIN-DIPYRIDAMOLE ER, BUPIVACAINE-KETOROLAC-KETAMINE, BUTALBITAL-ASPIRIN-CAFFEINE, CALDOLOR, CARISOPRODOL-ASPIRIN, CARISOPRODOL-ASPIRIN-CODEINE, CELEBREX, CELECOXIB, COMBOGESIC, COMBOGESIC IV, CONSENSI, COXANTO, DICLOFENAC, DICLOFENAC POTASSIUM, DICLOFENAC SODIUM, DICLOFENAC SODIUM ER, DICLOFENAC SODIUM MICRONIZED, DICLOFENAC SODIUM-MISOPROSTOL, DIFLUNISAL, DOLOBID, DURLAZA, EC-NAPROSYN, ELYXYB, ETODOLAC, ETODOLAC ER, FELDENE, FENOPROFEN CALCIUM, FENOPRON, HYDROCODONE-IBUPROFEN, IBU, IBUPAK, IBUPROFEN, IBUPROFEN LYSINE, IBUPROFEN-FAMOTIDINE, INDOCIN, INDOMETHACIN, INDOMETHACIN ER, INFLAMMACIN, INFLATHERM(DICLOFENAC-MENTHOL), KETOPROFEN, KETOPROFEN MICRONIZED, KETOROLAC TROMETHAMINE, LODINE, LOFENA, MECLOFENAMATE SODIUM, MEFENAMIC ACID, MELOXICAM, NABUMETONE, NABUMETONE MICRONIZED, NALFON, NAPRELAN, NAPROSYN, NAPROTIN, NAPROXEN, NAPROXEN SODIUM, NAPROXEN SODIUM CR, NAPROXEN SODIUM ER, NAPROXEN-ESOMEPRAZOLE MAG, NEOPROFEN, NORGESIC, NORGESIC FORTE, ORPHENADRINE-ASPIRIN-CAFFEINE, ORPHENGESIC FORTE, OXAPROZIN, PIROXICAM, R.E.C.K.(ROPIV-EPI-CLON-KETOR), RELAFEN DS, ROPIVACAINE-CLONIDINE-KETOROLC, ROPIVACAINE-KETOROLAC-KETAMINE, SPRIX, SULINDAC, SUMATRIPTAN SUCC-NAPROXEN SOD, SYMBRAVO, TOLECTIN 600, TOLMETIN SODIUM, TORONOVA II SUIK, TORONOVA SUIK, TOXICOLOGY SALIVA COLLECTION, TRESNI, TREXIMET, VIMOVO, VIVLODEX, XIFYRM, YOSPRALA, ZIPSOR, ZORVOLEX, ZYNRELEF
Selected CYP2D6 Substrates/Terbinafine SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Terbinafine is a strong inhibitor of CYP2D6 and may convert patients from the extensive metabolizer to poor metabolizer phenotype for this enzyme.(1) CLINICAL EFFECTS: Concurrent use of terbinafine may result in increased serum levels and adverse effects of drugs primarily metabolized by or sensitive to changes in the activity of the CYP2D6 metabolic pathway.(1,2) PREDISPOSING FACTORS: With paroxetine, the risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(3) PATIENT MANAGEMENT: Terbinafine has a serum half-life of approximately 36 hours, so the maximal effect of this interaction may be delayed for one to two weeks. Extended monitoring may be necessary. Patients receiving therapy with agents primarily metabolized by CYP2D6 need increased monitoring for adverse effects and may need a dose reduction. Plasma level monitoring should be considered in patients receiving flecainide.(4) The effect of terbinafine on CYP2D6 substrates may last for up to four weeks after terbinafine discontinuation. Over time, patients previously stabilized on the combination of terbinafine and a selected CYP2D6 substrate may need an increase in the dose of the CYP2D6 metabolized drug. DISCUSSION: In a randomized, placebo-controlled trial in 12 healthy subjects, terbinafine (150 mg daily for 6 days) increased the area-under-curve (AUC) and maximum concentration (Cmax) of a single dose of paroxetine (20 mg) by 2.9-fold and 1.9-fold, respectively.(6) In a placebo-controlled trial in 12 healthy males, terbinafine (250 mg for 4 days) increased the Cmax and AUC of a single dose of venlafaxine (75 mg) by 2.67-fold and 4.9-fold, respectively.(7) CYP2D6 substrates linked to this monograph are: dapoxetine, flecainide, metoprolol, nebivolol, paroxetine, perphenazine, propafenone, propranolol, venlafaxine and yohimbine.	TERBINAFINE HCL
SSRIs;SNRIs/Slt Anticoagulants;Antiplatelets;Thrombolytics SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Serotonin release by platelets plays a role in hemostasis.(1,2) The increased risk of bleeding may be a result of a decrease in serotonin reuptake by platelets. CLINICAL EFFECTS: Concurrent use of a selective serotonin reuptake inhibitor(1-6) or a serotonin-norepinephrine reuptake inhibitor(7-9) and agents that affect coagulation may result in bleeding. PREDISPOSING FACTORS: The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Renal impairment has been associated with an elevated risk of GI bleed in patients on SSRIs.(15) Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs). PATIENT MANAGEMENT: Selective serotonin reuptake inhibitors(1-6) or serotonin-norepinephrine reuptake inhibitors(7-9) and agents that affect coagulation should be used concurrently with caution. If concurrent therapy is warranted, monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin, hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. When applicable, perform agent-specific laboratory test (e.g. INR, aPTT) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. DISCUSSION: In a retrospective review of 5 years of data from the Pharmaco-Epidemiologic Prescription Database, hospitalizations for upper gastro-intestinal bleeding in antidepressant users were compared to those in non-antidepressant users. The risk of a bleed in a patient using an NSAID only based on an observed-expected ration was 4.5 and in a patient using low-dose aspirin only was 2.5. Concurrent use of a selective serotonin reuptake inhibitor with NSAIDs or low-dose aspirin increased the risk of bleeding to 12.2 and 5.2, respectively.(10) In another study, there were 16 cases of upper gastrointestinal bleeding in patients receiving concurrent therapy with selective serotonin reuptake inhibitors and NSAIDs. Adjusted relative risk of bleeding with NSAIDs, selective serotonin reuptake inhibitors, or both were 3.7, 2.6, or 15.6, respectively.(11) In a case-control study conducted in users of acenocoumarol or phenprocoumon, 1848 patients who had been hospitalized with abnormal bleeding were each matched to 4 control patients. When patients took both a SSRI and a coumarin, an increased risk of hospitalization due to major non-gastrointestinal bleeding was observed (adjusted OR 1.7), but not due to gastrointestinal bleeding (adjusted OR 0.8).(12) A retrospective review examined patients discharged from a hospital with antiplatelet therapy following a myocardial infarction. When compared to aspirin therapy alone, both aspirin therapy with a SSRI and aspirin, clopidogrel, and SSRI therapy were associated with an increased risk of bleeding (hazard ratios 1.42 and 2.35, respectively.) Compared with dual antiplatelet therapy (aspirin and clopidogrel), use of aspirin and clopidogrel and a SSRI was also associated with increased risk of bleeding (hazard ratio 1.57).(13) In The Rotterdam Study, fluvoxamine increased the risk of over anticoagulation (hazard ratio 2.63). Paroxetine was not associated with an increased risk. There were insufficient numbers of patients taking other SSRIs to assess increased risk.(14) A self-controlled case study of 1,622 oral anticoagulant-precipitant drug pairs were reviewed and found 14% of drug pairs were associated with a statistically significant elevated risk of thromboembolism. Concurrent use of dabigatran and citalopram resulted in a ratio of rate ratios (95% CI) of 1.69 (1.11-2.57).(16) A systematic review and meta-analysis of 22 cohort and case-controlled studies including over 1 million patients found 1.55-fold higher odds of upper gastrointestinal (GI) bleeding in SSRI users compared with non-SSRI users (95% CI, 1.35-1.78). In subgroup analyses, the risk was found to be greatest among participants taking SSRIs concurrently with NSAIDs or antiplatelet medications.(17)	ACD-A, ACTIVASE, AGGRASTAT, ARGATROBAN, ARGATROBAN-0.9% NACL, ARIXTRA, ASPIRIN-DIPYRIDAMOLE ER, BRILINTA, CATHFLO ACTIVASE, CITRATE PHOSPHATE DEXTROSE, DABIGATRAN ETEXILATE, DEFITELIO, DICUMAROL, DIPYRIDAMOLE, EFFIENT, ELIQUIS, ELMIRON, ENOXAPARIN SODIUM, ENOXILUV, EPTIFIBATIDE, FONDAPARINUX SODIUM, FRAGMIN, HEPARIN SODIUM, HEPARIN SODIUM IN 0.45% NACL, HEPARIN SODIUM-0.45% NACL, HEPARIN SODIUM-0.9% NACL, HEPARIN SODIUM-D5W, KENGREAL, LOVENOX, PENTOSAN POLYSULFATE SODIUM, PHENINDIONE, PRADAXA, PRASUGREL HCL, RIVAROXABAN, SAVAYSA, TICAGRELOR, TIROFIBAN HCL, TNKASE, XARELTO, ZONTIVITY
Selected SSRIs; SNRIs/Clopidogrel SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Serotonin release by platelets plays a role in hemostasis.(1,2) The increased risk of bleeding may be a result of a decrease in serotonin reuptake by platelets. CLINICAL EFFECTS: Concurrent use of a selective serotonin reuptake inhibitor(1-5) or a serotonin-norepinephrine reuptake inhibitor(7-9) and agents that affect coagulation may result in bleeding.(12) PREDISPOSING FACTORS: The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Renal impairment has been associated with an elevated risk of GI bleed in patients on SSRIs.(13) Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs). PATIENT MANAGEMENT: Selective serotonin reuptake inhibitors(1-5) or serotonin-norepinephrine reuptake inhibitors(6-8) and agents that affect coagulation should be used concurrently with caution. If concurrent therapy is warranted, monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin, hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. Discontinue antiplatelet agents in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. DISCUSSION: In a retrospective review of 5 years of data from the Pharmaco-Epidemiologic Prescription Database, hospitalizations for upper gastro-intestinal bleeding in antidepressant users were compared to those in non-antidepressant users. The risk of a bleed in a patient using an NSAID only based on an observed-expected ratio was 4.5 and in a patient using low-dose aspirin only was 2.5. Concurrent use of a selective serotonin reuptake inhibitor with NSAIDs or low-dose aspirin increased the risk of bleeding to 12.2 and 5.2, respectively.(9) In another study, there were 16 cases of upper gastrointestinal bleeding in patients receiving concurrent therapy with selective serotonin reuptake inhibitors and NSAIDs. Adjusted relative risk of bleeding with NSAIDs, selective serotonin reuptake inhibitors, or both were 3.7, 2.6, or 15.6, respectively.(10)	CLOPIDOGREL, CLOPIDOGREL BISULFATE, PLAVIX
Select Serotonergic Agents/Fentanyl SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Although the exact mechanism is not known, fentanyl is thought to have mild serotonergic effects.(1,7) Concurrent administration with one or more potent serotonergic agents may increase serotonin effects, leading to toxicity. CLINICAL EFFECTS: Concurrent use of serotonergic agents and fentanyl may result in serotonin syndrome. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity.(1) PREDISPOSING FACTORS: Based upon case reports, high fentanyl doses in the perioperative period, concomitant use of multiple serotonergic agents, or a recent increase in dosage of either agent may be risk factors for this interaction.(2-6) PATIENT MANAGEMENT: Most patients tolerate the combination of fentanyl with serotonin-increasing agents. Serotonin syndrome constitutes a range of toxicities from mild to life threatening.(1) Monitor patients on multiple serotonergic agents for symptoms of serotonin toxicity. If concurrent therapy is warranted, patients should be monitored for signs and symptoms of serotonin syndrome. Instruct patients to report muscle twitching, tremors, shivering and stiffness, fever, heavy sweating, heart palpitations, restlessness, confusion, agitation, trouble with coordination, or severe diarrhea. Patients in whom serotonin syndrome is suspected should receive immediate medical attention. DISCUSSION: Health Canada recently reported 5 cases of serotonin syndrome associated with patients receiving fentanyl and at least one other serotonergic agent.(2) Additional cases have been reported in the medical literature.(3-6) Serotonin increasing agents linked to this monograph are: citalopram, clomipramine, desvenlafaxine, duloxetine, fluoxetine, imipramine, levomilnacipran, milnacipran, paroxetine, sertraline, venlafaxine, vilazodone and vortioxetine.	FENTANYL, FENTANYL CITRATE, FENTANYL CITRATE-0.9% NACL, FENTANYL CITRATE-D5W, FENTANYL CITRATE-STERILE WATER, FENTANYL CITRATE-WATER, FENTANYL-BUPIVACAINE-0.9% NACL, FENTANYL-BUPIVACAINE-NACL, FENTANYL-ROPIVACAINE-0.9% NACL, FENTANYL-ROPIVACAINE-NACL
Eliglustat/Weak CYP2D6 Inhibitors SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Weak inhibitors of CYP2D6 may inhibit the metabolism of eliglustat. If the patient is also taking an inhibitor of CYP3A4, eliglustat metabolism can be further inhibited.(1) CLINICAL EFFECTS: Concurrent use of an agent that is a weak inhibitor of CYP2D6 may result in elevated levels of and clinical effects of eliglustat, including prolongation of the PR, QTc, and/or QRS intervals, which may result in life-threatening cardiac arrhythmias.(1) PREDISPOSING FACTORS: If the patient is also taking an inhibitor of CYP3A4 and/or has hepatic impairment, eliglustat metabolism can be further inhibited.(1) The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(2) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(2) PATIENT MANAGEMENT: The dosage of eliglustat with weak inhibitors of CYP2D6 in poor CYP2D6 metabolizers should be limited to 84 mg daily.(1) The dosage of eliglustat with weak inhibitors of CYP2D6 in extensive CYP2D6 metabolizers with mild (Child-Pugh Class A) hepatic impairment should be limited to 84 mg daily.(1) If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting. DISCUSSION: Paroxetine (30 mg daily), a strong inhibitor of CYP2D6, increased eliglustat (84 mg BID) maximum concentration (Cmax) and area-under-curve (AUC) by 7-fold and 8.4-fold, respectively, in extensive metabolizers. Physiologically-based pharmacokinetic (PKPB) models suggested paroxetine would increase eliglustat Cmax and AUC by 2.1-fold and 2.3-fold, respectively, in intermediate metabolizers. PKPB models suggested ketoconazole may increase the Cmax and AUC of eliglustat (84 mg daily) by 4.3-fold and 6.2-fold, respectively, in poor metabolizers.(1) PKPB models suggested terbinafine, a moderate inhibitor of CYP2D6, would increase eliglustat Cmax and AUC by 3.8-fold and 4.5-fold, respectively, in extensive metabolizers and by 1.6-fold and 1.6-fold, respectively in intermediate metabolizers. PKPB models suggest that concurrent eliglustat (84 mg BID), paroxetine (a strong inhibitor of CYP2D6), and ketoconazole would increase eliglustat Cmax and AUC by 16.7-fold and 24.2-fold, respectively, in extensive metabolizers. In intermediate metabolizers, eliglustat Cmax and AUC would be expected to increase 7.5-fold and 9.8-fold, respectively.(1) PKPB models suggest that concurrent eliglustat (84 mg BID), terbinafine (a moderate inhibitor of CYP2D6), and ketoconazole would increase eliglustat Cmax and AUC by 10.2-fold and 13.6-fold, respectively, in extensive metabolizers. In intermediate metabolizers, eliglustat Cmax and AUC would be expected to increase 4.2-fold and 5-fold, respectively.(1) A single dose of rolapitant increased dextromethorphan, a CYP2D6 substrate, about 3-fold on days 8 and day 22 following administration. Dextromethorphan levels remained elevated by 2.3-fold on day 28 after single dose rolapitant. The inhibitory effects of rolapitant on CYP2D6 are expected to persist beyond 28 days.(5) Weak inhibitors of CYP2D6 include: alogliptin, artesunate, celecoxib, chloroquine, clobazam, clomipramine, desvenlafaxine, dimenhydrinate, diphenhydramine, dronabinol, dupilumab, echinacea, enasidenib, felodipine, gefitinib, hydralazine, hydroxychloroquine, lorcaserin, methadone, panobinostat, propafenone, sertraline, vemurafenib, and venlafaxine.(3,4)	CERDELGA
Bupropion/SNRIs; SSRIs SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Both bupropion and the SSRIs and SNRIs are known to lower the seizure threshold.(1,2) In addition, bupropion, a strong inhibitor of CYP2D6, may inhibit the metabolism of SSRIs and SNRIs metabolized by CYP2D6. The potential for bupropion to inhibit the metabolism of the antidepressant differs. Antidepressants that are very sensitive to CYP2D6 inhibition have a greater potential for increased effects. Antidepressants which are very sensitive to CYP2D6 inhibition and have the greatest potential for increased effects are: fluoxetine,(3) paroxetine,(4) and venlafaxine.(5) Antidepressants which are moderately sensitive to CYP2D6 inhibition are: fluvoxamine.(6) Antidepressants which are metabolized by CYP2D6 but less susceptible to CYP2D6 inhibition and therefore have a lower potential for increased effects are: citalopram(7) and duloxetine.(8) CLINICAL EFFECTS: Concurrent use of bupropion and a SSRI or SNRI may result in additive effects on the seizure threshold, increasing the risk of seizures.(1,2) Concurrent use may also increase levels of and side effects from antidepressants metabolized by CYP2D6, such as citalopram, duloxetine, fluoxetine, fluvoxamine, paroxetine, and venlafaxine.(3-10) PREDISPOSING FACTORS: The risk of seizures may be increased in patients with a history of head trauma or prior seizure; CNS tumor; severe hepatic cirrhosis; excessive use of alcohol or sedatives; addiction to opiates, cocaine, or stimulants; use of over-the-counter stimulants an anorectics; a total daily dose of bupropion greater than 450 mg or single doses greater than 150 mg; rapid escalation of bupropion dosage; diabetics treated with oral hypoglycemics or insulin; or with concomitant medications known to lower seizure threshold (antipsychotics, theophylline, systemic steroids).(1,2) With paroxetine, the risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(11) PATIENT MANAGEMENT: The concurrent use of bupropion and SSRIs or SNRIs should be undertaken only with extreme caution and with low initial bupropion dosing and small gradual dosage increases.(1,2) Single doses should not exceed 150 mg.(1,2) The maximum daily dose of bupropion should not exceed 300 mg for smoking cessation(2) or 450 mg for depression.(1) DISCUSSION: Because of the risk of seizure from concurrent bupropion and other agents that lower seizure threshold, the manufacturer of bupropion states that the concurrent use of bupropion and antidepressants should be undertaken only with extreme caution and with low initial bupropion dosing and small gradual dosage increases.(1,2) In a study in 15 male subjects who were extensive metabolizers of CYP2D6, bupropion (150 mg twice daily) increased the maximum concentration (Cmax), area-under-curve (AUC), and half-life (T1/2) of a single dose of desipramine (50 mg) by 2-fold, 5-fold, and 2-fold, respectively.(1,2) In a clinical study, citalopram steady state levels were not significantly different in poor metabolizers and extensive metabolizers of CYP2D6. Coadministration of a drug that inhibits CYP2D6 with citalopram is unlikely to have clinically significant effects on citalopram metabolism, based on the study results in CYP2D6 poor metabolizers.(7) Concomitant use of duloxetine (40 mg once daily) with paroxetine (20 mg once daily) increased the AUC of duloxetine by about 60%.(8) An in vivo study of single-dose fluvoxamine evaluated pharmacokinetic changes in 13 poor metabolizers (PM) compared to 16 extensive metabolizers (EM). The mean Cmax, AUC, and half-life were increased by 52%, 200%, and 62%, respectively, in the PM compared to the EM group.(6) Fluoxetine, paroxetine, and venlafaxine are classified as sensitive CYP2D6 substrates with an increase in AUC >= 5-fold.(9) The FDA defines sensitive substrates as drugs that have an increase in AUC >= 5-fold and moderate sensitive substrates have an increase in AUC >= 2-fold to <5-fold when administered with strong inhibitors.(10)	APLENZIN, AUVELITY, BUPROPION HCL, BUPROPION HCL SR, BUPROPION XL, CONTRAVE, FORFIVO XL, WELLBUTRIN SR, WELLBUTRIN XL
Desvenlafaxine; Venlafaxine/Selected Tricyclic Compounds SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Desvenlafaxine or venlafaxine may impair the oxidative hepatic metabolism of tricyclic compounds via CYP2D6. CLINICAL EFFECTS: Concurrent administration of desvenlafaxine or venlafaxine with a tricyclic compound may result in an increase in serum levels, toxicities, and/or clinical effects of the tricyclic compound. PREDISPOSING FACTORS: The risk of seizures may be increased in patients with a history of head trauma or prior seizure; CNS tumor; severe hepatic cirrhosis; excessive use of alcohol or sedatives; addiction to opiates, cocaine, or stimulants; use of over-the-counter stimulants and anorectics; diabetics treated with oral hypoglycemics or insulin; or with concomitant medications known to lower seizure threshold (antipsychotics, theophylline, systemic steroids). The risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(5) PATIENT MANAGEMENT: Patients should be observed for increased adverse effects and clinical effects of tricyclic compounds at the initiation of concurrent therapy with desvenlafaxine or venlafaxine. Plasma concentrations of the tricyclic compound should be monitored and the dosage adjusted accordingly. If desvenlafaxine or venlafaxine is discontinued in a patient receiving a tricyclic compound, the dosage of the tricyclic compound may need to be adjusted. The US manufacturer of desvenlafaxine recommends the dose of desipramine be reduced by up to one-half when administered with desvenlafaxine 400 mg. DISCUSSION: In a 70 year old patient, the use of venlafaxine, fluoxetine, and nortriptyline was associated with severe anticholinergic side effects. This interaction was thought to be due to increased nortriptyline levels. A case report of anticholinergic toxic syndrome with venlafaxine and desipramine combination exist as well. Concomitant administration of desvenlafaxine 400 mg with a single 50 mg dose of desipramine resulted in an increase in the Cmax and AUC of desipramine by approximately 50% and 90%. The affinity of the different SSRIs, SNRIs, and tricyclics for CYP P-450 may vary.	AMITRIPTYLINE HCL, AMOXAPINE, ANAFRANIL, CHLORDIAZEPOXIDE-AMITRIPTYLINE, CLOMIPRAMINE HCL, DESIPRAMINE HCL, DOXEPIN HCL, IMIPRAMINE HCL, IMIPRAMINE PAMOATE, NORPRAMIN, NORTRIPTYLINE HCL, PAMELOR, PERPHENAZINE-AMITRIPTYLINE, PROTRIPTYLINE HCL, SILENOR, TRIMIPRAMINE MALEATE
Selected SSRIs; SNRIs/Cyclobenzaprine SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Selected serotonin or serotonin-norepinephrine reuptake inhibitors (SSRIs or SNRIs) may impair the oxidative hepatic metabolism of cyclobenzaprine. Cyclobenzaprine is metabolized by CYP1A2, CYP3A4, and to a lesser extent CYP2D6.(4) Fluvoxamine is a strong inhibitor of CYP1A2 and a weak inhibitor of CYP3A4 and CYP2D6. Sertraline and venlafaxine are weak inhibitors of CYP2D6. CLINICAL EFFECTS: Concurrent administration of selected SSRIs or SNRIs with cyclobenzaprine may result in an increase in serum levels, toxicities, and/or clinical effects of cyclobenzaprine, including serotonin syndrome.(4) Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity. PREDISPOSING FACTORS: The risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(5) PATIENT MANAGEMENT: Patients should be observed for increased adverse effects and clinical effects of cyclobenzaprine at the initiation of concurrent therapy with selected SSRIs or SNRIs. Plasma concentrations of cyclobenzaprine should be monitored and the dosage adjusted accordingly. If concurrent therapy is warranted, patients should be monitored for signs and symptoms of serotonin syndrome, and seizure activity. Instruct patients to report muscle twitching, tremors, shivering and stiffness, fever, heavy sweating, heart palpitations, restlessness, confusion, agitation, trouble with coordination, or severe diarrhea. If the SSRI or SNRI is discontinued in a patient receiving cyclobenzaprine, the dosage of the cyclobenzaprine may need to be adjusted. DISCUSSION: There have been case reports of serotonin syndrome with trazodone and amitriptyline with lithium, and cyclobenzaprine with duloxetine.(6) The affinity of the different SSRIs, SNRIs, and tricyclics for CYP P-450 may vary.	AMRIX, CYCLOBENZAPRINE HCL, CYCLOBENZAPRINE HCL ER, CYCLOPAK, CYCLOTENS, FEXMID
Selected SSRIs; SNRIs/Trazodone SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Selected serotonin or serotonin-norepinephrine reuptake inhibitors (SSRIs or SNRIs) may impair the oxidative hepatic metabolism of trazodone. Trazodone is metabolized by CYP3A4 and its active metabolite meta-chlorophenylpiperazine (m-CPP) is metabolized by CYP2D6. Duloxetine is a moderate inhibitor of CYP2D6. Desvenlafaxine, fluvoxamine, sertraline, and venlafaxine are weak inhibitors of CYP2D6. Fluvoxamine is also a weak inhibitor of CYP3A4. CLINICAL EFFECTS: Concurrent administration of selected SSRIs or SNRIs with trazodone may result in an increase in serum levels, toxicities (e.g. torsades de pointes), and/or clinical effects of trazodone. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity. PREDISPOSING FACTORS: The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(5) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibitors its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(5) PATIENT MANAGEMENT: Patients should be observed for increased adverse effects and clinical effects of trazodone at the initiation of concurrent therapy with selected SSRIs or SNRIs. Plasma concentrations of trazodone should be monitored and the dosage adjusted accordingly. If the SSRI or SNRI is discontinued in a patient receiving trazodone, the dosage of trazodone may need to be adjusted. If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting. If concurrent therapy is warranted, patients should be monitored for signs and symptoms of serotonin syndrome. Instruct patients to report muscle twitching, tremors, shivering and stiffness, fever, heavy sweating, heart palpitations, restlessness, confusion, agitation, trouble with coordination, or severe diarrhea. DISCUSSION: There have been case reports of serotonin syndrome with trazodone and amitriptyline with lithium, and cyclobenzaprine (structurally related to the TCAs) with duloxetine.(3) The affinity of the different selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors, and tricyclics for CYP P-450 may vary.	RALDESY, TRAZODONE HCL
SNRIs/Flurbiprofen SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Serotonin release by platelets plays a role in hemostasis.(1,2) The increased risk of bleeding may be a result of a decrease in serotonin reuptake by platelets. CLINICAL EFFECTS: Concurrent use of a serotonin-norepinephrine reuptake inhibitor(1-3) and flurbiprofen may result in bleeding. PREDISPOSING FACTORS: The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs). PATIENT MANAGEMENT: Serotonin-norepinephrine reuptake inhibitors(1-3) and flurbiprofen should be used concurrently with caution. Patients should be warned about the increased risk of bleeding and be educated about signs and symptoms of bleeding.(1-4) If concurrent therapy is warranted, monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin, hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. Discontinue anti-platelet agents in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. DISCUSSION: In a retrospective review of 5 years of data from the Pharmaco-Epidemiologic Prescription Database, hospitalizations for upper gastro-intestinal bleeding in antidepressant users were compared to those in non-antidepressant users. The risk of a bleed in a patient using an NSAID only based on an observed-expected ratio was 4.5 and in a patient using low-dose aspirin only was 2.5. Concurrent use of a selective serotonin reuptake inhibitor with NSAIDs or low-dose aspirin increased the risk of bleeding to 12.2 and 5.2, respectively.(4) In another study, there were 16 cases of upper gastrointestinal bleeding in patients receiving concurrent therapy with selective serotonin reuptake inhibitors and NSAIDs. Adjusted relative risk of bleeding with NSAIDs, selective serotonin reuptake inhibitors, or both were 3.7, 2.6, or 15.6, respectively.(5)	FLURBIPROFEN, LURBIRO
SNRIs/Selected NSAIDs SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Serotonin release by platelets plays a role in hemostasis.(1,2) The increased risk of bleeding may be a result of a decrease in serotonin reuptake by platelets. CLINICAL EFFECTS: Concurrent use of a serotonin-norepinephrine reuptake inhibitor(1-3) and a NSAID may result in bleeding. PREDISPOSING FACTORS: The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs). PATIENT MANAGEMENT: Serotonin-norepinephrine reuptake inhibitors(1-3) and NSAIDs should be used concurrently with caution. Patients should be warned about the increased risk of bleeding and be educated about signs and symptoms of bleeding.(1-4) If concurrent therapy is warranted, monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin, hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. Discontinue anti-platelet agents in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. DISCUSSION: In a retrospective review of 5 years of data from the Pharmaco-Epidemiologic Prescription Database, hospitalizations for upper gastro-intestinal bleeding in antidepressant users were compared to those in non-antidepressant users. The risk of a bleed in a patient using an NSAID only based on an observed-expected ratio was 4.5 and in a patient using low-dose aspirin only was 2.5. Concurrent use of a selective serotonin reuptake inhibitor with NSAIDs or low-dose aspirin increased the risk of bleeding to 12.2 and 5.2, respectively.(4) In another study, there were 16 cases of upper gastrointestinal bleeding in patients receiving concurrent therapy with selective serotonin reuptake inhibitors and NSAIDs. Adjusted relative risk of bleeding with NSAIDs, selective serotonin reuptake inhibitors, or both were 3.7, 2.6, or 15.6, respectively.(5)	BROMFENAC SODIUM, PHENYLBUTAZONE
Tramadol/Selected SSRIs; SNRIs SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: The concurrent administration of tramadol with a selective serotonin reuptake inhibitor (SSRI) or a serotonin/norepinephrine reuptake inhibitor (SNRI) may result in additive blockade of serotonin reuptake, leading to central serotonergic hyperstimulation.(1) The combination of tramadol and SSRIs or SNRIs may also lower the seizure threshold.(1) CLINICAL EFFECTS: Concurrent administration may increase the risk for serotonin syndrome. Symptoms of serotonin syndrome may include tremor, agitation, diaphoresis, hyperreflexia, clonus, tachycardia, hyperthermia, and muscle rigidity.(2) Concurrent administration may increase the risk for seizures, especially in susceptible individuals.(1) PREDISPOSING FACTORS: Treatment with multiple medications which increase serotonin levels or with medications which inhibit the metabolism of serotonin increasing drugs are risk factors for serotonin syndrome.(2) Predisposing factors for a lower seizure threshold include a history of seizures, epilepsy, or a recognized risk for seizures (e.g. head trauma, metabolic disorders, alcohol, drug withdrawal, infections of the central nervous system). A genetic defect in CYP2D6 leading to the slow metabolizer phenotype may increase the risk for serotonin syndrome due to tramadol. PATIENT MANAGEMENT: If concurrent therapy of tramadol with a SSRI or SNRI is warranted, patients should be closely monitored for signs and symptoms of serotonin syndrome and increased seizure activity.(1) DISCUSSION: There are a number of serotonin syndrome case reports following the addition of tramadol to a stable selective serotonin reuptake inhibitor regimen. The syndrome developed between 12 hours to 3 weeks after the initiation of tramadol therapy. Patients recovered after tramadol and/or the SSRI/SNRI was discontinued.(3-14) One patient also developed mania.(3) Another patient developed nightmares and hallucinations after taking concurrent tramadol and paroxetine for 56 days.(15) One author suggests that although the combination of tramadol and SSRIs or SNRIs is associated with a risk for serotonin syndrome, given the high rate of co-prescribing for the combination it is an uncommon outcome.(16) A review of the 124 reports of seizures following tramadol therapy received by the FDA through July 31, 1996 revealed that 20 patients were receiving concurrent therapy with an selective serotonin reuptake inhibitor.(17) The manufacturer of tramadol states that the risk of seizure is increased in patients receiving concurrent therapy with selective serotonin reuptake inhibitors.(1) Selected SSRIs and SNRIs linked to this monograph include: citalopram, desvenlafaxine, escitalopram, fluvoxamine, levomilnacipran, milnacipran, sertraline, sibutramine, venlafaxine, vilazodone, and vortioxetine.	CONZIP, QDOLO, TRAMADOL HCL, TRAMADOL HCL ER, TRAMADOL HCL-ACETAMINOPHEN
Selected SSRIs;SNRIs/Cilostazol; Ticlopidine SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Serotonin release by platelets plays a role in hemostasis.(1) The increased risk of bleeding may be a result of a decrease in serotonin reuptake by platelets. CLINICAL EFFECTS: Concurrent use of a selective serotonin reuptake inhibitor(1-4) or a serotonin-norepinephrine reuptake inhibitor(5-7) and agents that affect coagulation may result in bleeding. PREDISPOSING FACTORS: The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Renal impairment has been associated with an elevated risk of GI bleed in patients on SSRIs.(8) Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs). PATIENT MANAGEMENT: Selective serotonin reuptake inhibitors(1-4) or serotonin-norepinephrine reuptake inhibitors(5-7) and agents that affect coagulation should be used concurrently with caution. If concurrent therapy is warranted, monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin, hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. When applicable, perform agent-specific laboratory test (e.g. INR, aPTT) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. DISCUSSION: In a retrospective review of 5 years of data from the Pharmaco-Epidemiologic Prescription Database, hospitalizations for upper gastro-intestinal bleeding in antidepressant users were compared to those in non-antidepressant users. The risk of a bleed in a patient using an NSAID only based on an observed-expected ration was 4.5 and in a patient using low-dose aspirin only was 2.5. Concurrent use of a selective serotonin reuptake inhibitor with NSAIDs or low-dose aspirin increased the risk of bleeding to 12.2 and 5.2, respectively.(9) In another study, there were 16 cases of upper gastrointestinal bleeding in patients receiving concurrent therapy with selective serotonin reuptake inhibitors and NSAIDs. Adjusted relative risk of bleeding with NSAIDs, selective serotonin reuptake inhibitors, or both were 3.7, 2.6, or 15.6, respectively.(10) In a case-control study conducted in users of acenocoumarol or phenprocoumon, 1848 patients who had been hospitalized with abnormal bleeding were each matched to 4 control patients. When patients took both a SSRI and a coumarin, an increased risk of hospitalization due to major non-gastrointestinal bleeding was observed (adjusted OR 1.7), but not due to gastrointestinal bleeding (adjusted OR 0.8).(11) A retrospective review examined patients discharged from a hospital with antiplatelet therapy following a myocardial infarction. When compared to aspirin therapy alone, both aspirin therapy with a SSRI and aspirin, clopidogrel, and SSRI therapy were associated with an increased risk of bleeding (hazard ratios 1.42 and 2.35, respectively.) Compared with dual antiplatelet therapy (aspirin and clopidogrel), use of aspirin and clopidogrel and a SSRI was also associated with increased risk of bleeding (hazard ration 1.57).(12) In The Rotterdam Study, fluvoxamine increased the risk of over anticoagulation (hazard ratio 2.63). Paroxetine was not associated with an increased risk. There were insufficient numbers of patients taking other SSRIs to assess increased risk.(13)	CILOSTAZOL
Tamoxifen/Selected Weak CYP2D6 Inhibitors SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Inhibitors of CYP2D6 may inhibit the conversion of tamoxifen to endoxifen (an active metabolite of tamoxifen).(1-2) The role of endoxifen in tamoxifen's efficacy has been debated and may involve a minimum concentration level.(3-5) CLINICAL EFFECTS: Concurrent use of inhibitors of CYP2D6 may decrease the effectiveness of tamoxifen in preventing breast cancer recurrence. PREDISPOSING FACTORS: Concurrent use of weak CYP2D6 inhibitors in patients who are CYP2D6 intermediate metabolizers should be avoided. Patients who are CYP2D6 poor metabolizers lack CYP2D6 function and are not affected by CYP2D6 inhibition. PATIENT MANAGEMENT: Although data on this interaction are conflicting, it may be prudent to use alternatives to CYP2D6 inhibitors when possible in patients taking tamoxifen. The US manufacturer of tamoxifen states that the impact on the efficacy of tamoxifen by strong CYP2D6 inhibitors is uncertain and makes no recommendation regarding coadministration with inhibitors of CYP2D6.(12) The manufacturer of paroxetine (a strong CYP2D6 inhibitor) states that alternative agents with little or no CYP2D6 inhibition should be considered.(13) The National Comprehensive Cancer Network's breast cancer guidelines advises caution when coadministering strong CYP2D6 inhibitors with tamoxifen.(14) If concurrent therapy is warranted, the risks versus benefits should be discussed with the patient. DISCUSSION: Some studies have suggested that administration of fluoxetine, paroxetine, and quinidine with tamoxifen or a CYP2D6 poor metabolizer phenotype may result in a decrease in the formation of endoxifen (an active metabolite of tamoxifen) and a shorter time to breast cancer recurrence.(1-2,9) A retrospective study of 630 breast cancer patients found an increasing risk of breast cancer mortality with increasing durations of coadministration of tamoxifen and paroxetine. In the adjusted analysis, absolute increases of 25%, 50%, and 75% in the proportion of time of overlapping use of tamoxifen with paroxetine was associated with 24%, 54%, and 91% increase in the risk of death from breast cancer, respectively.(15) The CYP2D6 genotype of the patient may have a role in the effects of this interaction. Patients with wild-type CYP2D6 genotype may be affected to a greater extent by this interaction. Patients with a variant CYP2D6 genotype may have lower baseline levels of endoxifen and may be affected to a lesser extent by this interaction.(6-10) In a retrospective review, 1,325 patients treated with tamoxifen for breast cancer were classified as being poor 2D6 metabolizers (lacking functional CYP2D6 enzymes), intermediate metabolizers (heterozygous alleles), or extensive metabolizers (possessing 2 functional alleles). After a mean follow-up period of 6.3 years, the recurrence rates were 14.9%, 20.9%, and 29.0%, in extensive metabolizers, intermediate metabolizers, and poor metabolizers, respectively.(11) In October of 2006, the Advisory Committee Pharmaceutical Science, Clinical Pharmacology Subcommittee of the US Food and Drug Administration recommended that the US tamoxifen labeling be updated to include information about the increased risk of breast cancer recurrence in poor CYP2D6 metabolizers (either by genotype or drug interaction).(16-17) The labeling changes were never made due to ongoing uncertainty about the effects of CYP2D6 genotypes on tamoxifen efficacy. In contrast to the above information, two studies have shown no relationship between CYP2D6 genotype and breast cancer outcome.(18-20) As well, a number of studies found no association between use of CYP2D6 inhibitors and/or antidepressants in patients on tamoxifen and breast cancer recurrence,(21-25) though the studies were limited by problematic selection of CYP2D6 inhibitors and short follow-up. Weak CYP2D6 inhibitors include: amiodarone, chlorpromazine, citalopram, escitalopram, flecainide, methadone, panobinostat, propafenone, telithromycin, vemurafenib, and venlafaxine.(26-27)	SOLTAMOX, TAMOXIFEN CITRATE
Dextromethorphan/Selected Serotonergic Agents SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Dextromethorphan inhibits neuronal reuptake of serotonin. Concurrent administration with one or more serotonergic agents may increase serotonin effects, leading to serotonin toxicity.(1-11) CLINICAL EFFECTS: The concurrent use of dextromethorphan with serotonergic agents may increase the risk for serotonin syndrome. Serotonin syndrome constitutes a range of toxicities from mild to life threatening.(3) Mild serotonin symptoms may include: shivering, diaphoresis, mydriasis, intermittent tremor, and/or myoclonus.(3) Moderate serotonin symptoms may include: tachycardia, hypertension, hyperthermia, mydriasis, diaphoresis, hyperactive bowel sounds, hyperreflexia, and/OR clonus.(3) Severe serotonin symptoms may include: severe hypertension and tachycardia, shock, agitated delirium, muscular rigidity, and/or hypertonicity.(3) PREDISPOSING FACTORS: Concurrent use of additional drugs which increase CNS serotonin levels would be expected to further increase risk for serotonin syndrome.(1-11) PATIENT MANAGEMENT: Monitor patients on multiple serotonergic agents for symptoms of serotonin toxicity. Patients in whom serotonin syndrome is suspected should receive immediate medical attention. If the interacting agents are prescribed by different providers, it would be prudent to assure that both are aware of concomitant therapy and monitoring the patient for serotonin toxicities. Advise patients not to exceed recommended dosages of dextromethorphan. If concurrent therapy is warranted, patients should be monitored for signs and symptoms of serotonin syndrome. Instruct patients to report muscle twitching, tremors, shivering and stiffness, fever, heavy sweating, heart palpitations, restlessness, confusion, agitation, trouble with coordination, or severe diarrhea. DISCUSSION: Dextromethorphan inhibits neuronal reuptake of serotonin and may potentially precipitate dose-dependant serotonin toxicity in conjunction with other serotonergic agents.(4,5) Serotonin syndrome has been reported in patients following the addition of dextromethorphan containing cough syrups to duloxetine,(6) escitalopram,(7) fluoxetine,(8,9) paroxetine,(10) and sertraline.(11) Selected serotonergic agents linked to this monograph include: citalopram, clomipramine, duloxetine, escitalopram, fluvoxamine, imipramine, levomilnacipran, milnacipran, sertraline, venlafaxine, vilazodone and vortioxetine.	AUVELITY, BROMFED DM, BROMPHENIRAMINE-PSEUDOEPHED-DM, DEXTROMETHORPHAN HBR, NUEDEXTA, PROMETHAZINE-DM
Ziprasidone/Serotonergic Agents SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Ziprasidone is a 5-HT1A agonist and serotonin and norepinephrine reuptake inhibitor. Concurrent administration with one or more serotonergic agents may increase serotonin effects, resulting in serotonin toxicity.(1,2) CLINICAL EFFECTS: Concurrent use of ziprasidone and other serotonergic agents may result in serotonin syndrome, a potentially life-threatening condition with symptoms including altered mental status, hypertension, restlessness, myoclonus, hyperthermia, hyperreflexia, diaphoresis, shivering, and tremor.(1) PREDISPOSING FACTORS: Serotonin syndrome risk is dose-related. Higher systemic concentrations of either drug would be predicted to increase risk for serotonin toxicity.(2) Concomitant therapy with multiple agents which increase brain serotonin concentrations may also increase risk for serotonin syndrome.(2) PATIENT MANAGEMENT: Caution patients about the risk of serotonin syndrome with the concomitant use of ziprasidone with other serotonergic drugs. Instruct patients to contact their healthcare provider, or report to the emergency room, should they experience signs or symptoms of serotonin syndrome.(1) DISCUSSION: Several cases of serotonin syndrome have been reported in patients receiving ziprasidone.(4-6)	GEODON, ZIPRASIDONE HCL, ZIPRASIDONE MESYLATE

The following contraindication information is available for VENLAFAXINE HCL (venlafaxine hcl):

Overview
Contraindicated
Severe
Moderate

Drug contraindication overview.

*Known hypersensitivity to venlafaxine hydrochloride, venlafaxine besylate, desvenlafaxine succinate, or to any excipients in the formulation. *Concurrent or recent (i.e., within 14 days) therapy with monoamine oxidase inhibitors (MAOIs), including linezolid and IV methylene blue.

There are 0 contraindications.

There are 17 severe contraindications. Adequate patient monitoring is recommended for safer drug use.

Severe List
Angle-closure glaucoma
Bipolar disorder
Child-pugh class A hepatic impairment
Child-pugh class B hepatic impairment
Child-pugh class C hepatic impairment
Chronic kidney disease stage 2 (mild) GFR 60-89 ml/min
Chronic kidney disease stage 3A (moderate) GFR 45-59 ml/min
Chronic kidney disease stage 3B (moderate) GFR 30-44 ml/min
Chronic kidney disease stage 4 (severe) GFR 15-29 ml/min
Chronic kidney disease stage 5 (failure) GFr<15 ml/min
Disease of liver
Hypertension
Risk of angle-closure glaucoma due to narrow angle of anterior chamber of eye
Seizure disorder
Serotonin syndrome
Severe hepatic disease
Suicidal ideation

There are 7 moderate contraindications. Clinically significant contraindication, where the condition can be managed or treated before the drug may be given safely.

Moderate List
Hypercholesterolemia
Hyponatremia
Increased risk of bleeding
Increased risk of bleeding due to coagulation disorder
Kidney disease with likely reduction in glomerular filtration rate (GFr)
SIADH syndrome
Weight loss

The following adverse reaction information is available for VENLAFAXINE HCL (venlafaxine hcl):

Overview
Severe
Less Severe

Adverse reaction overview.

Adverse events reported in >=5% of patients receiving venlafaxine hydrochloride conventional tablets include asthenia, sweating, nausea, constipation, anorexia, vomiting, somnolence, dry mouth, dizziness, nervousness, anxiety, tremor and blurred vision, and abnormal ejaculation/orgasm and impotence in men. Adverse events reported in >=5% of patients receiving venlafaxine hydrochloride extended-release capsules (Effexor XR(R)) include sweating, nausea, anorexia, somnolence, dry mouth, constipation, abnormal ejaculation, impotence in men, and libido decreased. The safety of venlafaxine besylate extended-release tablets is based on the extended-release capsules.

Adverse events reported in >=5% of patients receiving venlafaxine hydrochloride extended-release tablets for major depressive disorder include sweating, GI complaints (nausea, dry mouth, anorexia), CNS complaints (dizziness, somnolence, abnormal dreams), and abnormal ejaculation. Adverse events reported in >=5% of patients receiving venlafaxine hydrochloride extended-release tablets for social anxiety disorder include asthenia, sweating, GI complaints (anorexia, dry mouth, nausea), CNS complaints (anxiety, insomnia, libido decreased, nervousness, somnolence, dizziness), abnormalities of sexual function (abnormal ejaculation, orgasmic dysfunction, impotence), yawning, and abnormal vision.

There are 50 severe adverse reactions.

More Frequent	Less Frequent
Headache disorder	Abnormal sexual function Akathisia Chest pain Hypertension Increased urinary frequency Pruritus of skin Tachycardia Urinary retention

Rare/Very Rare
Accommodation disorder Acquired dystonia Agranulocytosis Altered mental status Anaphylaxis Angioedema Aplastic anemia Chronic heart failure Deep venous thrombosis Dyspnea Dysuria Eosinophilic pneumonia Erythema multiforme Extrapyramidal disease Gastrointestinal hemorrhage Hemorrhage Hepatitis Hyponatremia Hypotension Interstitial pneumonitis Manic disorder Mood changes Neuroleptic malignant syndrome Ocular hypertension Orthostatic hypotension Pancreatitis Peripheral edema Rhabdomyolysis Secondary angle-closure glaucoma Seizure disorder Serotonin syndrome SIADH syndrome Stevens-johnson syndrome Suicidal ideation Syncope Takotsubo cardiomyopathy Tardive dyskinesia Thrombocytopenic disorder Torsades de pointes Toxic epidermal necrolysis Ventricular fibrillation

Rare/Very Rare

Accommodation disorder
Acquired dystonia
Agranulocytosis
Altered mental status
Anaphylaxis
Angioedema
Aplastic anemia
Chronic heart failure
Deep venous thrombosis
Dyspnea
Dysuria
Eosinophilic pneumonia
Erythema multiforme
Extrapyramidal disease
Gastrointestinal hemorrhage
Hemorrhage
Hepatitis
Hyponatremia
Hypotension
Interstitial pneumonitis
Manic disorder
Mood changes
Neuroleptic malignant syndrome
Ocular hypertension
Orthostatic hypotension
Pancreatitis
Peripheral edema
Rhabdomyolysis
Secondary angle-closure glaucoma
Seizure disorder
Serotonin syndrome
SIADH syndrome
Stevens-johnson syndrome
Suicidal ideation
Syncope
Takotsubo cardiomyopathy
Tardive dyskinesia
Thrombocytopenic disorder
Torsades de pointes
Toxic epidermal necrolysis
Ventricular fibrillation

There are 77 less severe adverse reactions.

More Frequent	Less Frequent
Anorexia Blurred vision Constipation Disorder of ejaculation Dizziness Drowsy Dysgeusia Erectile dysfunction General weakness Hyperhidrosis Libido changes Nausea Symptoms of anxiety Tremor Visual changes Vomiting Xerostomia	Acute cognitive impairment Bronchitis Chills Diarrhea Dream disorder Dyspepsia Edema Flatulence Hostility Hypercholesterolemia Irritability Migraine Muscle fasciculation Neck pain Nervousness Orgasm disorder Skin rash Tinnitus Vaginitis Vertigo Weight gain Weight loss

Rare/Very Rare
Abnormal hepatic function tests Abnormal vaginal bleeding Accidental fall Acute abdominal pain Aggressive behavior Agitation Alopecia Anticholinergic toxicity Ataxia Bruxism Delirium Depersonalization Dysmenorrhea Ecchymosis Epistaxis Eructation Exophthalmos Flu-like symptoms Flushing Hyperacusis Hyperprolactinemia Hypertonia Hypomania Impulse control disorder Insomnia Menorrhagia Muscle rigidity Mydriasis Palpitations Paresthesia Proteinuria Rhinitis Sinusitis Skin photosensitivity Trismus Urticaria Vasodilation of blood vessels Yawning

Rare/Very Rare

Abnormal hepatic function tests
Abnormal vaginal bleeding
Accidental fall
Acute abdominal pain
Aggressive behavior
Agitation
Alopecia
Anticholinergic toxicity
Ataxia
Bruxism
Delirium
Depersonalization
Dysmenorrhea
Ecchymosis
Epistaxis
Eructation
Exophthalmos
Flu-like symptoms
Flushing
Hyperacusis
Hyperprolactinemia
Hypertonia
Hypomania
Impulse control disorder
Insomnia
Menorrhagia
Muscle rigidity
Mydriasis
Palpitations
Paresthesia
Proteinuria
Rhinitis
Sinusitis
Skin photosensitivity
Trismus
Urticaria
Vasodilation of blood vessels
Yawning

The following precautions are available for VENLAFAXINE HCL (venlafaxine hcl):

Pediatric
Pregnant
Lactation
Geriatric

The safety and effectiveness of venlafaxine in pediatric patients have not been established; venlafaxine is not approved for use in pediatric patients. In 2 placebo-controlled trials in 766 pediatric patients with major depressive disorder and 2 placebo-controlled trials in 793 pediatric patients with generalized anxiety disorder, there were insufficient data to establish the safety and efficacy of venlafaxine for pediatric patients with these conditions. Additionally, studies with venlafaxine hydrochloride extended-release capsules suggest that their use in pediatric patients may adversely affect weight and height; decreases in appetite and weight loss have also been observed.

Studies conducted in pediatric patients 6 to 17 years of age have found that blood pressure and cholesterol increases observed with venlafaxine are clinically relevant and similar to increases seen in adults. An increased risk of suicidal thoughts and behaviors was observed in pediatric patients treated with antidepressants.

Contraindicated

None

Severe Precaution

None

Management or Monitoring Precaution

None

A National Pregnancy Registry for Antidepressants is available that monitors pregnancy outcomes in females exposed to antidepressants during pregnancy. Clinicians are encouraged to register patients by calling the National Pregnancy Registry for Antidepressants at 1-844-405-6185 or by visiting online at https://womensmentalhealth.org/clinical-and-research-programs/pregnancyregi stry/antidepressants/.

Available epidemiologic data with venlafaxine in pregnant females have not established a drug-associated risk of major birth defects, miscarriage, or other adverse developmental outcomes. Epidemiologic data found that exposure to SNRIs (including venlafaxine), particularly in the month before delivery, has been associated with a less than 2-fold increase in the risk of postpartum hemorrhage. Observational studies have identified a potential increased risk for preeclampsia when venlafaxine is used during mid to late pregnancy.

There are risks associated with untreated depression in pregnancy and poor neonatal adaptation in newborns with exposure to SNRIs during pregnancy. In animal reproductive studies, no evidence of malformations or fetotoxicity was observed when venlafaxine was administered during the period of organogenesis at doses up to 2.5 or 4 times the maximum recommended human dose (MRHD) on a mg/m2 basis in rats and rabbits, respectively.

However, an increase in postnatal mortality and decreased pup weights at 2.5 times the MRHD were observed with administration of venlafaxine to pregnant rats during gestation and lactation. Neonates exposed to SNRIs late in the third trimester of pregnancy have developed complications requiring hospitalization, respiratory support, and tube feeding that can arise immediately upon delivery.

Clinical findings reported to date in neonates have included respiratory distress, cyanosis, apnea, seizures, temperature instability, feeding difficulty, vomiting, hypoglycemia, hypotonia, hypertonia, hyperreflexia, tremors, jitteriness, irritability, and constant crying. These clinical features appear to be consistent with either a direct toxic effect of the SNRI or possibly a drug withdrawal syndrome. It should be noted that, in some cases, the clinical picture was consistent with serotonin syndrome.

Neonates exposed to venlafaxine during the third trimester of pregnancy should be monitored for discontinuation syndrome. When treating a pregnant female during the third trimester, carefully consider the potential risks and benefits of treatment.

Venlafaxine and its active metabolite are present in human milk and have not shown adverse reactions in breast-fed infants. It is not known if venlafaxine affects milk production. Consider the developmental and health benefits of breastfeeding, the mother's clinical need for the drug, and the potential for adverse effects on the breast-fed infant from exposure to venlafaxine or the underlying maternal condition.

In clinical studies with venlafaxine hydrochloride extended-release tablets in major depressive disorder, generalized anxiety disorder, social anxiety disorder, and panic disorder, there were 4, 6, 1, and 2% of patients who were >=65 years of age, respectively. In clinical studies with venlafaxine hydrochloride conventional tablets, 12% of patients were >=65 years of age. Overall differences in efficacy and safety have not been observed between geriatric patients and younger patients. Geriatric patients may have greater sensitivity to medications and may also be at greater risk of developing hyponatremia.

The following icd codes are available for VENLAFAXINE HCL (venlafaxine hcl)'s list of indications:

Major depressive disorder
F32.0	Major depressive disorder, single episode, mild
F32.1	Major depressive disorder, single episode, moderate
F32.2	Major depressive disorder, single episode, severe without psychotic features
F32.3	Major depressive disorder, single episode, severe with psychotic features
F32.4	Major depressive disorder, single episode, in partial remission
F32.5	Major depressive disorder, single episode, in full remission
F32.9	Major depressive disorder, single episode, unspecified
F33	Major depressive disorder, recurrent
F33.0	Major depressive disorder, recurrent, mild
F33.1	Major depressive disorder, recurrent, moderate
F33.2	Major depressive disorder, recurrent severe without psychotic features
F33.3	Major depressive disorder, recurrent, severe with psychotic symptoms
F33.4	Major depressive disorder, recurrent, in remission
F33.40	Major depressive disorder, recurrent, in remission, unspecified
F33.41	Major depressive disorder, recurrent, in partial remission
F33.42	Major depressive disorder, recurrent, in full remission
F33.9	Major depressive disorder, recurrent, unspecified