PREZISTA (darunavir ethanolate)

There are 30 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
Protease Inhibitors/Oral Midazolam; Triazolam 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: The protease inhibitors may inhibit the metabolism of the benzodiazepines midazolam and triazolam at CYP3A4.(1-30) CLINICAL EFFECTS: Concurrent administration may result in increased levels and clinical effects of the benzodiazepines, which may result in profound sedation, respiratory depression, coma, and/or death.(1-30) Higher triazolam levels may increase risk for anterograde amnesia, "sleep driving" and other complex behavior disorders.(30) PREDISPOSING FACTORS: The elderly are particularly sensitive to increased plasma concentrations of triazolam.(30) PATIENT MANAGEMENT: The manufacturers of the protease inhibitors and US guidelines on use of antiretroviral agents (31) state that concurrent administration of triazolam or oral midazolam with ritonavir-boosted(1-3) darunavir,(4-6) lopinavir,(7-9) nirmatrelvir,(10) paritaprevir,(11) saquinavir,(12-14) or tipranavir (15-17); ritonavir-boosted or unboosted amprenavir,(18-19) atazanavir,(20-21) fosamprenavir,(22-23) indinavir,(24-26); or nelfinavir,(27-29) is contraindicated. Midazolam may be administered by the intravenous route in patients with close clinical monitoring for respiratory depression and/or prolonged sedation. Caution should be exercised and dosage adjustments should be considered if these effects occur. DISCUSSION: In an open-label, randomized study in 14 subjects, lopinavir/ ritonavir (400/100 mg twice daily) decreased the metabolism of single doses of oral and intravenous midazolam (0.025 mg/kg and 5 mg, respectively) by 77% and 92%, respectively.(32) In a double-blind, randomized, cross-over study in 12 subjects, concurrent administration of saquinavir base with oral midazolam increased the bioavailability of oral midazolam from 41% to 90%. The midazolam maximum concentration (Cmax) and area-under-curve (AUC) increased two-fold and five-fold, respectively. The concurrent administration of saquinavir base with intravenous midazolam resulted in a decrease in midazolam clearance by 56% and increased the midazolam half-life from 4.1 hours to 9.5 hours.(33) In a study in 6 healthy subjects, saquinavir base (1200 mg twice daily) increased the AUC and Cmax of a single dose of midazolam (7.5 mg) by 514% and 235%, respectively.(12) In a study in 16 healthy subjects, saquinavir/ritonavir (1000/100 mg twice daily) increased the AUC and Cmax of a single dose of midazolam (7.5 mg) by 1144% and 327%, respectively.(14) In a double-blind study, ritonavir (four doses of 200 mg) decreased the clearance of a single dose of triazolam (0.125 mg) by 96%.(34) Amprenavir,(35), lopinavir,(36) and ritonavir(33,34) have been shown to inhibit triazolam metabolism in vitro in human liver microsomes. In a clinical trial of 13 healthy patients patients receiving concurrent midazolam (3mg) and ritonavir (100 mg three times daily), midazolam AUC increased by a factor of 28.4 +/- 4.2 and oral clearance was reduced to 4.2% of normal.(37) Protease inhibitors linked to this monograph include: amprenavir, atazanavir, fosamprenavir, darunavir, indinavir, lopinavir, nelfinavir, nirmatrelvir, paritaprevir, saquinavir, and tipranavir. Ritonavir, as a pharmacokinetic booster, will alert through the primary protease inhibitor.	HALCION, MIDAZOLAM, MIDAZOLAM HCL, TRIAZOLAM
Selected Protease Inhibitors; Cobicistat/Pimozide 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: Protease inhibitors(1-13,15) and cobicistat(14) may inhibit the metabolism of pimozide at CYP3A4. CLINICAL EFFECTS: Concurrent administration may result in elevated levels of pimozide, which may result in prolongation of the QTc interval and potentially life-threatening ventricular arrhythmias.(1-15) 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.(17) 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).(17) 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.(18) PATIENT MANAGEMENT: The concurrent use of pimozide and the protease inhibitors amprenavir,(1) atazanavir,(2,3) darunavir,(4) fosamprenavir,(5) indinavir,(6,7) nelfinavir,(6,8) nirmatrelvir coadministered with ritonavir,(15) and tipranavir coadministered with ritonavir(13) and cobicistat(14) is contraindicated. If concurrent therapy is deemed medically necessary, 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: An in vitro study indicates that pimozide is metabolized at CYP3A4.(15) Elevated levels of pimozide may prolong the QTc interval resulting in life-threatening ventricular arrhythmias.(6) Selected CYP3A inhibitors linked include: amprenavir, atazanavir, cobicistat, darunavir, fosamprenavir, indinavir, nelfinavir, nirmatrelvir, paritaprevir, and tipranavir.	PIMOZIDE
Protease Inhibitors/Ergot Alkaloids 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: The protease inhibitors may inhibit the metabolism of the ergot alkaloids by CYP3A4, including dihydroergotamine, ergotamine, ergonovine, and methylergonovine. (1-13) CLINICAL EFFECTS: The concurrent administration of a protease inhibitor with an ergot alkaloid may result in elevated levels, clinical effects, and adverse effects of the ergot alkaloids.(1-13) Signs of ergotism may include peripheral vasospasm and ischemia. PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The concurrent administration of ergot alkaloids with amprenavir,(1) atazanavir,(2,3) darunavir,(4) fosamprenavir,(5) indinavir, (6) the combination of lopinavir and ritonavir,(7) nelfinavir,(8) nirmatrelvir coadministered with ritonavir,(25) ritonavir, (12) saquinavir,(9,10) and tipranavir coadministered with ritonavir(11) is contraindicated. The US manufacturer of methylergonovine states that methylergonovine should not be administered with potent CYP3A4 inhibitors such as protease inhibitors.(13) Protease inhibitors linked include: amprenavir, atazanavir, darunavir, fosamprenavir, indinavir, lopinavir, nelfinavir, nirmatrelvir, ritonavir, saquinavir, and tipranavir. DISCUSSION: There have been several case reports of ergotism developing in patients receiving concurrent ergotamine derivatives with indinavir,(14) nelfinavir,(15) or ritonavir.(16-23) 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.	DIHYDROERGOTAMINE MESYLATE, ERGOLOID MESYLATES, ERGOMAR, ERGOTAMINE TARTRATE, ERGOTAMINE-CAFFEINE, METHYLERGONOVINE MALEATE, METHYSERGIDE MALEATE, MIGERGOT, MIGRANAL, TRUDHESA
Selected CYP3A4 Substrates/Rifampin 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: Rifampin may increase the metabolism of the protease inhibitors(1-12) and cobicistat(13) by inducing CYP3A4. CLINICAL EFFECTS: Concurrent use of rifampin with protease inhibitors may result in decreased levels and clinical effectiveness of the protease inhibitors(1-12,14) and cobicistat.(13) Concurrent use of rifampin with the combination of saquinavir/ritonavir may result in drug-induced hepatitis.(1,14-16) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The manufacturers of atazanavir,(3,4), cobicistat,(12) darunavir,(5) fosamprenavir,(6) the combination of lopinavir and ritonavir,(8) nelfinavir,(9) saquinavir,(1,11) and tipranavir(12) state that concurrent use of rifampin is contraindicated. The manufacturers of amprenavir,(2) indinavir,(7) and ritonavir(10) state that these agents should not be used with rifampin. The manufacturer of rifampin states that concurrent use of atazanavir, darunavir, fosamprenavir, saquinavir, and tipranavir is contraindicated.(14) The Department of Health and Human Services (DHHS) Guidelines for the Use of Antiretroviral Agents states that rifampin is contraindicated for patients on boosted or unboosted protease inhibitors. Additional ritonavir does not overcome the interaction and may increase hepatotoxicity, and additional cobicistat is not recommended. DHHS recommends use of rifabutin as an alternative.(17) The CDC/NIH guidelines on treatment of opportunistic infections (OI) in HIV(18) and the CDC's guidelines on managing drug interactions in HIV-related tuberculosis (TB)(19) provide guidance for the use of rifampin with the combination product of lopinavir/ritonavir when rifabutin is not available. The OI guidelines recommend increasing the dose of lopinavir/ritonavir by 50%, and subsequently, increasing to a full double dose, when used with rifampin. Transaminases should be monitored more frequently than usual. The guidelines on drug interactions in HIV-related TB state that higher doses of lopinavir/ritonavir should be used only when close monitoring for hepatotoxicity is possible, and when there is a pressing need to start antiretroviral therapy and other antiretrovirals are not an option. In adults, it is recommended to increase the dose of lopinavir/ritonavir by 50% (to 600/150 mg) for one week, then to double the dose (to 800/200 mg). In children, "super-boosted" lopinavir/ritonavir is recommended, achieved by using pediatric weight-based dosing for lopinavir/ritonavir, plus additional ritonavir to reach milligram to milligram parity of lopinavir and ritonavir doses. For both double dosing and super-boosting, the guidelines caution that unacceptable rates of hepatotoxicity was seen in healthy volunteers, though early clinical experience in HIV+ adults found that double dosing was reasonably well tolerated. DISCUSSION: The concurrent administration of amprenavir and rifampin decreased amprenavir maximum concentration (Cmax), area-under-curve (AUC), and minimum concentration (Cmin) by 70%, 82%, and 92%, respectively. There was no change in rifampin Cmax or AUC.(2,6,20) In a study in 16 subjects, concurrent rifampin (600 mg daily) and atazanavir/ritonavir (300/100 mg daily) decreased atazanavir Cmax, AUC, and Cmin by 53%, 72%, and 98%, respectively.(3) In a study in 12 healthy, HIV-negative subjects, concurrent rifampin (600 mg daily) and indinavir (800 mg three times daily) decreased indinavir Cmax and AUC by 87% and 92%, respectively.(7) In a study in 6 HIV-positive subjects, concurrent indinavir/ritonavir (800/100 mg twice daily) and rifampin (300 mg daily) decreased the AUC of indinavir and ritonavir by 87% and 94%, respectively.(21) In a study in 11 HIV-positive subjects, concurrent indinavir (800 mg three times daily) increased the AUC of a dose of rifampin (600 mg) by 73%.(22) The concurrent administration of lopinavir/ritonavir (400/100 mg twice daily for 20 days) and rifampin (600 mg daily for 10 days) in 22 subjects decreased lopinavir Cmax, AUC, and Cmin by 55%, 75%, and 99%, respectively. Concurrent administration of lopinavir/ritonavir (800/200 mg twice daily for 9 days) and rifampin (600 mg daily for 14 days) in 10 subjects did not change lopinavir Cmax and decreased lopinavir AUC and Cmin by 16% and 57%, respectively. Concurrent lopinavir/ritonavir (400/400 mg twice daily for 9 days) and rifampin (600 mg daily for 14 days) in 9 subjects decreased lopinavir Cmax and AUC by 7% and 2%, respectively, and did not change lopinavir Cmin. In these studies, 28% of subjects experienced a grade 2 increase in ALT/AST, of which 7 (21%) prematurely discontinued the study per protocol.(8) In an open-label, randomized study in 32 healthy subjects, all subjects initially received lopinavir/ritonavir 400/100 mg twice daily. During concurrent rifampin (600 mg daily), subjects received either 800/200 mg or 400/400 mg of lopinavir/ritonavir twice daily. Concurrent 800/200 mg lopinavir/ritonavir and rifampin decreased lopinavir Cmin by 57% but did not affect lopinavir Cmax. During concurrent 400/400 mg lopinavir/ritonavir and rifampin, lopinavir Cmin and Cmax were similar to levels seen with 400/100 mg lopinavir/ritonavir. Twelve subjects dropped out of the study and 9 developed elevated liver enzymes during concurrent therapy with lopinavir/ritonavir and rifampin.(23) Three studies examining double dosing (800/200 mg) or super-boosting (400/400 mg) of lopinavir/ritonavir with concurrent rifampin in HIV+ patients have been conducted. A study of double dosing and super-boosting in 18 HIV-TB patients(24) and a study of double dosing in 21 HIV+ patients without TB(25) both found that adequate lopinavir/ritonavir levels were achieved with lopinavir/ritonavir dose adjustments. In the study of HIV-TB patients, there were 3 isolated subtherapeutic lopinavir levels which were attributed to poor adherence. Ten of the 11 patients who were followed to completion of TB therapy had undetectable viral loads. There were no grade 3/4 adverse events, and 10 patients had mild side effects. In the study of patients without TB, two patients experienced grade 3/4 transaminitis, and other adverse events were mild. The third study of 25 HIV-TB patients confirmed the frequent but mild GI toxicity and reported that 2 patients had grade 3 transaminitis.(26) Concurrent administration of nelfinavir (750 mg three times daily) and rifampin (600 mg daily) in 12 subjects decreased nelfinavir AUC, Cmax, and Cmin by 83%, 76%, and 92%, respectively.(9) The concurrent administration of ritonavir and rifampin decreased the area-under-curve (AUC), maximum concentration (Cmax), and minimum concentration (Cmin) of ritonavir by 35%, 25%, and 49%, respectively.(10) The concurrent administration of saquinavir and rifampin in 14 subjects reduced the AUC and Cmax of saquinavir by 70% and 65%, respectively.(1,11) In a study in 28 healthy subjects, concurrent administration of rifampin (600 mg daily) with saquinavir (1000 mg twice daily) and ritonavir (100 mg twice daily), 65% (11/17) of subjects developed significant hepatocellular toxicity during the 28 day study. Transaminase elevations of up to greater than 20 times the upper limit of normal values were noted. One subject was admitted to the hospital. All study medications were discontinued in all subjects and all liver function tests were returning to normal. No deaths had been reported.(1,15,16) In an open-label, prospective, single arm study, 32 HIV-positive subjects received concurrent daily didanosine, lamivudine, ritonavir (200 mg), saquinavir (1600 mg), rifampin (600 mg), and isoniazid (300 mg). After 48 weeks, 62.5% had an HIV RNA level less than 50 copies/ml. Two patients had hepatic toxicity. In 10 subjects, saquinavir Cmin was less than 0.05 mcg/ml and 5 of these had virologic failure. Saquinavir Cmin was 44% lower during concurrent rifampin.(27) In an open-label, randomized, cross-over study, rifampin decreased saquinavir AUC by 70% in healthy subjects and by 46% in HIV-positive subjects.(28) 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.	RIFADIN, RIFAMPIN
Lovastatin; Simvastatin/Selected CYP3A4 Inhibitors 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: Strong CYP3A4 inhibitors may inhibit the metabolism of HMG-CoA reductase inhibitors that are metabolized by CYP3A4. CLINICAL EFFECTS: Concurrent administration may result in elevated HMG levels, which may increase the risk of myopathy, including rhabdomyolysis.(1-18) PREDISPOSING FACTORS: The risk for myopathy or rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of myopathy or rhabdomyolysis. Patients with a SLCO1B1 polymorphism that leads to decreased function of the hepatic uptake transporter OATP1B1 may have increased statin concentrations and be predisposed to myopathy or rhabdomyolysis. PATIENT MANAGEMENT: Do not use simvastatin with protease inhibitors,(1-3) with or without cobicistat(2,3) or ritonavir. The manufacturer of simvastatin states that the concurrent use of strong CYP3A4 inhibitors is contraindicated. The manufacturer of lovastatin states that the concurrent use of strong CYP3A4 inhibitors is contraindicated, including protease inhibitors, with or without cobicistat or ritonavir.(4, 25) The manufacturers of atazanavir,(5) cobicistat,(18) darunavir,(6) fosamprenavir,(7) indinavir,(8) the combination of lopinavir with ritonavir,(9) the combination of nirmatrelvir with ritonavir,(17) saquinavir,(11) and tipranavir(12) state that concurrent use of lovastatin or simvastatin is contraindicated. The manufacturer of nirmatrelvir/ritonavir recommends discontinuing use of lovastatin and simvastatin at least 12 hours prior to initiation of nirmatrelvir/ritonavir and holding statin therapy until 5 days after completing nirmatrelvir/ritonavir therapy.(17) The manufacturers of amprenavir(13) and nelfinavir(14) state that lovastatin and simvastatin should not be used with these agents. It would be prudent to utilize fluvastatin in patients treated with protease inhibitors who require HMG-CoA reductase therapy. DISCUSSION: A study in 15 subjects found that darunavir/ritonavir (300/100 mg twice daily) decreased the maximum concentration (Cmax) and area-under curve (AUC) of atorvastatin (10 mg daily) by 64% and 15%, when compared to atorvastatin (40 mg daily) administered alone. Atorvastatin minimum concentration (Cmin) increased by 81% during concurrent therapy.(6) A study in 16 subjects found that fosamprenavir increased atorvastatin Cmax and AUC by 304% and 130%, respectively. Atorvastatin Cmin decreased by 10%.(7) A study in 12 subjects found that lopinavir increased atorvastatin Cmax, AUC, and Cmin by 4.67-fold, 5.88-fold, and 2.28-fold, respectively. Atorvastatin had no clinically significant effect on lopinavir pharmacokinetics.(9) A study in 12 subjects found that lopinavir increased pravastatin Cmax and AUC by 1.26-fold and 1.33-fold, respectively. Pravastatin had no clinically significant effect on lopinavir pharmacokinetics.(9) A randomized, controlled trial in healthy subjects examined the effects of a combination of ritonavir and saquinavir on the pharmacokinetics of atorvastatin, pravastatin, and simvastatin and the effects of pravastatin on nelfinavir pharmacokinetics. The combination of ritonavir and saquinavir decreased pravastatin levels by 50% and increased atorvastatin and simvastatin levels by 79% and 3059%, respectively. Pravastatin had no statistically significant effect on nelfinavir pharmacokinetics.(14) An open-label study in healthy subjects examined the effects of nelfinavir on atorvastatin and simvastatin pharmacokinetics. Nelfinavir increased atorvastatin AUC, Cmax, and Cmin by 74%, 122%, and 39%, respectively. Nelfinavir increased simvastatin AUC and Cmax by 505% and 517%, respectively. There was no effect on nelfinavir pharmacokinetics when compared to historical controls.(14,16) A study in 14 healthy HIV-seronegative adults found that nelfinavir decreased median pravastatin AUC by 46.5%. Nelfinavir also decreased median pravastatin Cmax by 40.1%.(19) In a study of 25 HIV-positive patients, 13 patients were treated with pravastatin and 12 patients were treated with fluvastatin. Within the 25 patients, 8 patients were also on concomitant indinavir-containing highly active antiretroviral therapy (HAART). Indinavir plasma levels were not significantly influenced by pravastatin or fluvastatin therapy.(20) Rhabdomyolysis has been reported during concurrent use of simvastatin and nelfinavir(21) or ritonavir.(22) Lovastatin was tested in a single dose, open-labeled, randomized crossover study of ten healthy volunteers. Grapefruit juice increased Cmax of lovastatin 12-fold, and the area under the AUC 15-fold. Likewise, the active metabolite lovastatin acid demonstrated a 4-fold increase in Cmax and a 5-fold increase in AUC. Lovastatin and lovastatin acid concentrations and AUC increased in each subject.(23) A study found that itraconazole (200 mg for 4 days) increased lovastatin (40 mg on day 4)Cmax by greater than 25-fold and lovastatin acid AUC and Cmax by greater than 20-fold and 13-fold. A study found that itraconazole (100 mg for 4 days) increased lovastatin (40 mg on day 4) AUC and Cmax by greater than 14.8-fold and lovastatin acid AUC and Cmax by 15.4 and 11.5-fold.(25) 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.	ALTOPREV, EZETIMIBE-SIMVASTATIN, FLOLIPID, LOVASTATIN, SIMVASTATIN, VYTORIN, ZOCOR
Irinotecan/Strong CYP3A4 Inhibitors; Darunavir 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: Inhibitors of CYP3A4 may inhibit the metabolism of SN-38, the active metabolite of irinotecan. Strong CYP3A4 inhibitors and darunavir may prevent the breakdown of SN-38 to its inactive metabolites APC, NPC, M2, M3, and M4.(1,2) CLINICAL EFFECTS: Coadministration of irinotecan with a strong CYP3A4 inhibitor may result in increased irinotecan plasma concentration, and therefore increased exposure to its active metabolite SN-38. Increased SN-38 exposure may lead to serious toxicity, including severe neutropenia, interstitial pulmonary disease, and even death.(3) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Concurrent use of irinotecan and strong CYP3A4 inhibitors or darunavir is contraindicated.(2-4) Strong CYP3A4 inhibitors should be discontinued at least 1 week prior to starting irinotecan.(4) The US manufacturer of itraconazole states that concomitant administration with irinotecan is contra-indicated during and two weeks after itraconazole treatment.(5) If concurrent therapy is warranted, consider a four-fold reduction in irinotecan dose.(3) Patients receiving concurrent therapy should be closely monitored for toxicity. DISCUSSION: A randomized cross-over study involving seven patients was performed in which each was given irinotecan 350 mg/m2 IV alone for 90 minutes and followed 3 weeks later by irinotecan 100 mg/m2 given with ketoconazole 200 mg orally 1 hour before or 23 hours after the infusion of irinotecan, or both cycles were given vice versa. With ketoconazole coadministration, the conversion of irinotecan to its inactive metabolite was reduced by 87%, whereas the relative exposure to the active prodrug was increased by 109%. Both hematologic (degree of myelosuppression; percent decrease in neutrophil count) and nonhematologic (nausea, vomiting, and diarrhea) parameters were similar between the courses, despite a 3.5 fold reduced irinotecan dose when given in combination with ketoconazole. The authors concluded that the coadministration of various CYP3A4 inhibitors could potentiate a fatal outcome.(3) A prospective, open-label, randomized study was conducted to determine the pharmacokinetics of lopinavir (LPV)/ritonavir (RTV) administration with irinotecan (CPT11). Eight HIV-infected, Caucasian male patients with Kaposi's sarcoma, stage IV (according to New York University classification) were administered highly active antiretroviral therapy (HAART). HAART consisted of 400 mg lopinavir/ 100 mg ritonavir (Kaletra) twice daily (b.i.d) in association with NRTIs b.i.d. for at least 1 month before the start of anticancer chemotherapy. Patients were then treated with irinotecan as a single agent (150 mg/m2) over a 90 min infusion at days 1 and 10, every 3 weeks. Concomitant LPV/RTV treatment reduced the irinotecan clearance from 21.3 +/- 6.3 to 11.3 +/- 3.5 l/h/m2 (P=0.0008) causing an 89% increase of CPT11 AUC (P=0.001) and a 20% increase in the Cmax of CPT11 (p=0.02). The LPV/RTV treatment increased the AUC of SN38 by 204% (p=0.0001) and AUC of SN38G by 94% (P=0.002). Conversely, LPV/RTV treatment caused an 81% reduction in AUC of APC (p=0.02). Overall, the authors concluded that CYP3A4 inhibitors like LPV/RTV decrease CPT11 clearance and increase SN-38 exposure, potentially leading to CPT11 toxicity if not monitored closely.(7) Strong CYP3A4 Inhibitors include: adagrasib, boceprevir, ceritinib, clarithromycin, cobicistat, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, lonafarnib, lopinavir, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir, posaconazole, ribociclib, saquinavir, telaprevir, telithromycin, tipranavir, troleandomycin, tucatinib, and voriconazole.(8) 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.	CAMPTOSAR, IRINOTECAN HCL, ONIVYDE
Eplerenone/Strong CYP3A4 Inhibitors; Protease Inhibitors 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: Strong inhibitors of CYP3A4 and protease inhibitors may inhibit the metabolism of eplerenone.(1-3) CLINICAL EFFECTS: Concurrent use of eplerenone with a strong inhibitor of CYP3A4 or a protease inhibitor may result in 5-fold increases in eplerenone concentrations and toxicity (e.g. hyperkalemia, hypotension).(1-3) PREDISPOSING FACTORS: Severe renal disease increases the risk for hyperkalemia. PATIENT MANAGEMENT: The manufacturer of eplerenone states that the concurrent use of strong CYP3A4 inhibitors is contraindicated.(1) The US Department of Health and Human Services HIV guidelines state that protease inhibitors are contraindicated with eplerenone.(3) The US manufacturer of itraconazole states that concurrent use of eplerenone is contraindicated during and two weeks after itraconazole treatment.(4) The starting dose of eplerenone for hypertension should be reduced to 25 mg in patients receiving moderate CYP3A4 inhibitors.(1) In all patients taking eplerenone who start taking a moderate CYP3A4 inhibitor, check serum potassium and creatinine levels after 3-7 days of concurrent therapy.(1) DISCUSSION: Ketoconazole (200 mg BID) increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of eplerenone (100 mg) by 1.7-fold and 5.4-fold, respectively.(1) The concurrent use of eplerenone with less potent CYP3A4 inhibitors (erythromycin 500 mg BID, fluconazole 200 mg daily, saquinavir 1200 mg TID, and verapamil 240 mg daily) increased the Cmax of eplerenone by 1.4-fold to 1.6-fold and the AUC of eplerenone by 2.0-fold and 2.9-fold.(1) Strong inhibitors of CYP3A4 and protease inhibitors linked to this monograph include: adagrasib, amprenavir, atazanavir, boceprevir, ceritinib, clarithromycin, cobicistat, darunavir, fosamprenavir, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, lonafarnib, lopinavir, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir, posaconazole, ribociclib, saquinavir, telaprevir, telithromycin, tipranavir, troleandomycin, tucatinib, and voriconazole.(1,2)	EPLERENONE, INSPRA
Vardenafil (Greater Than 2.5 mg)/Selected Protease Inhibitors 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: Protease inhibitors may inhibit the metabolism of vardenafil by CYP3A4. CLINICAL EFFECTS: Concurrent use of vardenafil with protease inhibitors may result in increased levels of and adverse effects from vardenafil, including hypotension, visual changes, and sustained erections. PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: US guidelines for the use of antiretroviral agents recommends patients receiving protease inhibitors should receive no more than 2.5 mg of vardenafil every 72 hours. US labeling recommendations for concurrent use of vardenafil with protease inhibitors state: -Patients receiving any ritonavir- or cobicistat-containing regimens, including atazanavir, darunavir, fosamprenavir, indinavir, lopinavir, nirmatrelvir, paritaprevir, saquinavir, and tipranavir should receive no more than 2.5 mg of vardenafil every 72 hours. -Patients receiving unboosted atazanavir, unboosted fosamprenavir, unboosted indinavir, or nelfinavir should take no more than 2.5 mg of vardenafil every 24 hours. Canadian labeling contraindicates concurrent use of atazanavir/ritonavir, lopinavir/ritonavir, and nirmatrelvir/ritonavir with vardenafil.(6,13,17) Patients should be counseled that they are at an increased risk of vardenafil adverse effects, including hypotension, visual changes, and priapism. DISCUSSION: Concurrent use of indinavir (800 mg three times daily) with vardenafil (10 mg) increased the vardenafil area-under-curve (AUC) and maximum concentration (Cmax) by 16-fold and 7-fold, respectively. Vardenafil half-life increased 2-fold. At 24-hours post-dose, vardenafil levels fell to approximately 4% of vardenafil Cmax. The AUC and Cmax of indinavir decreased by 30% and 40%, respectively. Concurrent use of ritonavir (600 mg twice daily)with vardenafil (5 mg) increased vardenafil AUC and Cmax by 49-fold and 13-fold, respectively. The half-life of vardenafil increased to 26 hours. The ritonavir AUC and Cmax decreased by 20%.	VARDENAFIL HCL
Alfuzosin;Silodosin;Tamsulosin/Protease Inhibitors 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: The protease inhibitors may inhibit the metabolism of alfuzosin,(1) silodosin,(2) and tamsulosin(3) by CYP3A4. CLINICAL EFFECTS: Co-administration of a protease inhibitor may result in increased alfuzosin,(1) silodosin,(2) and tamsulosin(3) levels and serious effects such as hypotension. PREDISPOSING FACTORS: In patients receiving tamsulosin, the interaction may be worse in patients who are CYP2D6 poor metabolizers because tamsulosin also undergoes metabolism by this pathway.(3) PATIENT MANAGEMENT: The US manufacturers of alfuzosin(1) and silodosin(2) state that concurrent use of strong CYP3A4 inhibitors is contraindicated. The US manufacturer of tamsulosin states that tamsulosin should not be used with strong CYP3A4 inhibitors.(3) The US manufacturers of atazanavir,(4) darunavir,(5) fosamprenavir,(6) indinavir,(7) lopinavir/ritonavir,(8) nelfinavir,(9), nirmatrelvir/ritonavir,(10 paritaprevir, (11) saquinavir,(12) and tipranavir(13) state that concurrent use of alfuzosin is contraindicated. DISCUSSION: Administration of ketoconazole (400 mg daily), another inhibitor of CYP3A4, increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of alfuzosin (10 mg) by 2.3-fold and 3.2-fold, respectively.(1) Administration of ketoconazole (200 mg daily) increased the Cmax and AUC of a single dose of alfuzosin (10 mg) by 2.1-fold and 2.5-fold, respectively.(1) Administration of ketoconazole (200 mg daily for 4 days), increased the Cmax and AUC of a single dose of silodosin (4 mg) by 3.7-fold and 2.9-fold, respectively.(2) Administration of ketoconazole (400 mg daily for 4 days) increased the Cmax and AUC of a single dose of silodosin (8 mg) by 3.8-fold and 3.2-fold, respectively.(2) In a study in 24 healthy subjects, administration of ketoconazole (400 mg daily for 5 days) increased the Cmax and AUC of a single dose of tamsulosin (0.4 mg) by 2.2-fold and 2.8-fold, respectively.(3)	ALFUZOSIN HCL ER, DUTASTERIDE-TAMSULOSIN, FLOMAX, JALYN, RAPAFLO, SILODOSIN, TAMSULOSIN HCL, UROXATRAL
Ivabradine/Strong CYP3A4 Inhibitors; Protease Inhibitors 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: Strong inhibitors of CYP3A4 and protease inhibitors may inhibit the metabolism of ivabradine. Increased levels of ivabradine may cause ivabradine-induced reduction in heart rate which can contribute to increased QT prolongation risk.(1,2) CLINICAL EFFECTS: Concurrent use of strong inhibitors of CYP3A4 or protease inhibitors may result in elevated levels of and toxicity from ivabradine including a reduction in heart rate which can contribute to QT prolongation or torsades de pointes.(1,2) PREDISPOSING FACTORS: The risk of QT prolongation or torsade de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsade de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(3) 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 torsade 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).(3) PATIENT MANAGEMENT: The manufacturer of ivabradine states that concurrent use with strong CYP3A4 inhibitors is contraindicated.(1,2) Guideline recommendations state ivabradine should not be used with protease inhibitors.(4,5) The US manufacturer of itraconazole states that concurrent use with ivabradine is contraindicated during and two weeks after itraconazole treatment.(6) If concurrent therapy is deemed medically necessary, monitor patients receiving concurrent therapy for bradycardia (heart rate less than 50 bpm), dizziness, fatigue, hypotension, and/or symptoms of atrial fibrillation (heart palpitations, chest pressure, shortness of breath). DISCUSSION: Concurrent use of potent CYP3A4 inhibitors ketoconazole (200 mg daily) and josamycin (1000 mg twice daily) increased mean ivabradine plasma exposure by 7- to 8-fold.(1) CYP3A4 inhibitors linked to this monograph include: atazanavir, boceprevir, cobicistat, darunavir, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir, telaprevir, tipranavir, troleandomycin, and tucatinib.	CORLANOR, IVABRADINE HCL
Ranolazine/Strong CYP3A4 Inhibitors; Protease Inhibitors 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: Strong inhibitors of CYP3A4 and protease inhibitors may inhibit the metabolism of ranolazine.(1,2) CLINICAL EFFECTS: Concurrent use of strong inhibitors of CYP3A4 or protease inhibitors may result in elevated levels of and clinical effects from ranolazine. Elevated ranolazine levels may result in QTc prolongation, which may result in life-threatening cardiac arrhythmia, including torsades de pointes.(1,2) 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.(3) 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).(3) PATIENT MANAGEMENT: The concurrent use of ranolazine with strong CYP3A4 inhibitors or protease inhibitors is contraindicated.(1,2,4-8) The US HIV guidelines state that ranolazine (regardless of dose) is contraindicated with atazanavir when it is boosted with ritonavir. If atazanavir is not boosted with ritonavir, ranolazine should not be coadministered.(8) The US manufacturer of itraconazole states that concurrent administration of ranolazine is contraindicated during and two weeks after itraconazole treatment.(9) If concurrent therapy is deemed medically necessary, 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: Concurrent use of ketoconazole (200 mg twice daily), a strong CYP3A4 inhibitor, increased plasma levels of ranolazine (1000 mg twice daily) by 220%.(1) Concurrent use of diltiazem, a moderate inhibitor of CYP3A4 inhibitor, at daily doses of 180 mg to 360 mg increased plasma levels of ranolazine (1000 mg twice daily) by 50% and 140%, respectively.(1,2) Concurrent use of ranolazine (1000 mg twice daily) did not affect the pharmacokinetics of diltiazem (60 mg TID).(1) Concurrent use of verapamil (120 mg three times daily), a moderate inhibitor of CYP3A4 increased plasma levels of ranolazine (750 mg twice daily) by 100%.(1) Ranolazine-induced QTc prolongation is dose and concentration-related.(1,2) Strong CYP3A4 inhibitors and protease inhibitors linked to this monograph include: boceprevir; cobicistat; idelalisib; itraconazole; josamycin; ketoconazole; mibefradil; mifepristone; nefazodone; telaprevir; troleandomycin; tucatinib; ritonavir-boosted darunavir, nirmatrelvir, paritaprevir, and tipranavir; ritonavir-boosted or unboosted atazanavir or indinavir; and nelfinavir.(1,2,10,11) Ritonavir is always used with another protease inhibitor as a pharmacokinetic booster and is captured as part of the protease inhibitor regimen.	ASPRUZYO SPRINKLE, RANOLAZINE ER
Rivaroxaban/HIV Protease Inhibitors; Cobicistat 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: Rivaroxaban is metabolized by CYP3A4 and is a substrate of the P-glycoprotein (P-gp) efflux transport protein.(1-3) HIV protease inhibitors are CYP3A4 and P-gp inhibitors and may increase the absorption and decrease the elimination of rivaroxaban.(1-4) CLINICAL EFFECTS: Concurrent use of protease inhibitors may result in elevated levels and clinical effects of rivaroxaban, including an increased risk of bleeding.(1-4) 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: Recommendations for concurrent use of rivaroxaban and HIV protease inhibitors vary in different regions. The Australian(1) and Canadian(2) manufacturers of rivaroxaban state that the concurrent use of strong inhibitors of both P-gp and CYP3A4 with rivaroxaban is contraindicated. The UK manufacturer of rivaroxaban states that concurrent use of these agents is not recommended.(3) The US manufacturer of rivaroxaban states that concurrent use should be avoided.(4) The US manufacturer of atazanavir states that coadministration of atazanavir with ritonavir is not recommended. Coadministration of atazanavir alone should be monitored closely.(5) If concurrent therapy is warranted, monitor patients 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: Concurrent use of rivaroxaban with ritonavir (600 mg twice daily) increased rivaroxaban area-under-curve (AUC) and maximum concentration (Cmax) by 2.5-fold and 1.6-fold, respectively. There were also significant increases in pharmacodynamic effects.(1,2) HIV protease inhibitors linked to this monograph are: atazanavir, cobicistat, darunavir, fosamprenavir, indinavir, lopinavir, nelfinavir, saquinavir, and tipranavir.	RIVAROXABAN, XARELTO
Dronedarone/Strong CYP3A4 Inhibitors; Darunavir 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: Strong inhibitors of CYP3A4 may inhibit the metabolism of dronedarone.(1) CLINICAL EFFECTS: Concurrent use of a strong CYP3A4 inhibitor may result in prolongation of the QTc interval and life-threatening cardiac arrhythmias, including torsades de pointes.(1) PREDISPOSING FACTORS: The risk of QT prolongation or torsade de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsade 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 torsade 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, and/or renal/hepatic dysfunction).(2) PATIENT MANAGEMENT: The US manufacturer of dronedarone states that concurrent administration of strong CYP3A4 inhibitors is contraindicated.(1) The US manufacturer of darunavir states that concurrent use of dronedarone is contraindicated.(3) The US manufacturer of itraconazole states that concurrent administration of dronedarone is contraindicated during and two weeks after itraconazole treatment.(5) If alternatives are not available and concurrent therapy is deemed medically necessary, obtain serum calcium, magnesium, and potassium levels and monitor ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting. DISCUSSION: Concurrent use of ketoconazole and dronedarone (dosages not stated) increased the area-under-curve (AUC) and maximum concentration (Cmax) of dronedarone by 17-fold and 9-fold, respectively.(1) Strong CYP3A4 inhibitors linked to this monograph include: boceprevir, cobicistat, idelalisib, itraconazole, josamycin, ketoconazole, mibefradil, nefazodone, telaprevir, tucatinib, ritonavir-boosted darunavir, paritaprevir, and tipranavir, ritonavir-boosted or unboosted indinavir, and nelfinavir. Ritonavir is always used with another protease inhibitor as a pharmacokinetic booster and is captured as part of the protease inhibitor regimen. 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.	MULTAQ
Saxagliptin (>2.5 mg)/Strong CYP3A4 Inhibitors; Atazanavir; Darunavir 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: Strong inhibitors of CYP3A4 may inhibit the metabolism of saxagliptin.(1,2) CLINICAL EFFECTS: Concurrent use of a strong inhibitor of CYP3A4 may result in elevated levels and increased effects of saxagliptin.(1,2) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The US manufacturer of saxagliptin states that the dose of saxagliptin should be limited to 2.5 mg daily in patients taking strong inhibitors of CYP3A4.(1) DISCUSSION: Pretreatment with ketoconazole (200 mg every 12 hours for 9 days) increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of saxagliptin (100 mg) by 62% and 2.5-fold, respectively. The Cmax and AUC of the active metabolite of saxagliptin decreased 95% and 91%, respectively. The Cmax and AUC of ketoconazole decreased 16% and 13%, respectively.(1,2) Pretreatment with ketoconazole (200 mg every 12 hours for 7 days) increased the Cmax and AUC of a single dose of saxagliptin (100 mg) by 2.4-fold and 3.7-fold, respectively. The Cmax and AUC of the active metabolite of saxagliptin decreased 96% and 90%, respectively.(1) Inhibitors of CYP3A4 linked to this monograph include: adagrasib, atazanavir, boceprevir, ceritinib, clarithromycin, cobicistat, darunavir, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, lonafarnib, lopinavir/ritonavir, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir, posaconazole, ribociclib, saquinavir, telaprevir, telithromycin, tipranavir, tucatinib, and voriconazole.(1,3,4)	QTERN, SAXAGLIPTIN HCL, SAXAGLIPTIN-METFORMIN ER
Sildenafil (for PAH)/HIV Protease Inhibitors; Cobicistat 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: The metabolism of sildenafil by CYP3A4 may be inhibited by the protease inhibitors and cobicistat. CLINICAL EFFECTS: The concurrent administration of sildenafil with a protease inhibitor or cobicistat may result in elevated levels of sildenafil, which may result in increased adverse effects such as hypotension, syncope, visual changes, and priapism. PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The US manufacturers of atazanavir,(1) darunavir,(2) fosamprenavir,(3) indinavir,(4) lopinavir/ritonavir,(5) nelfinavir,(6) nirmatrelvir/ritonavir,(7) saquinavir,(9) tipranavir,(10) cobicistat(11), and ombitasvir-paritaprevir-ritonavir-dasabuvir(15) state that the concurrent use of sildenafil when used for the treatment of pulmonary arterial hypertension (PAH) is contraindicated. The US manufacturer of Revatio states that concurrent use is not recommended.(12) DISCUSSION: In a study in 16 subjects, administration of darunavir/ritonavir (400/100 mg twice daily) decreased the area-under-curve (AUC) and maximum concentration (Cmax) of a single dose of sildenafil (25 mg) by 38% and 3%, respectively, when compared to the administration of a 100 mg single dose of sildenafil given without darunavir.(3) In a study in 6 HIV-infected males, indinavir (800 mg every 8 hours) increased the AUC and Cmax of indinavir by 11% and 48%, respectively. Sildenafil AUC increased by 340%.(4) The concurrent administration of ritonavir (400 mg twice daily) at steady state with sildenafil (100 mg single dose) resulted in increases in the sildenafil Cmax and AUC by 300% (4-fold) and 1000% (11-fold), respectively.(7,12-14) After 24 hours, plasma levels of sildenafil were still approximately 200 ng/ml (normally 5 ng/ml 24 hours post-dose).(14) In a study in 27 healthy volunteers, the concurrent use of saquinavir (1200 mg 3 times daily for 8 days) increased the AUC and Cmax of a single dose of sildenafil (100 mg) by 210% and 140%, respectively.(9) Because a safe and effective dosage regimen for the use of sildenafil for PAH with concurrent protease inhibitor therapy has not been determined, the US manufacturer of the protease inhibitors state that concurrent use is contraindicated.(1-10,15)	REVATIO, SILDENAFIL CITRATE
Lurasidone/Protease Inhibitors; Cobicistat 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: Lurasidone is a sensitive substrate for CYP3A4.(1) Sensitive substrates will have at least a 5-fold increase in area-under-curve (AUC) when given with a strong inhibitor of the enzyme.(2) Protease inhibitors and cobicistat are strong and moderate inhibitors of CYP3A4 and may inhibit the metabolism of lurasidone.(1,3-5) CLINICAL EFFECTS: Concomitant use of lurasidone with inhibitors of CYP3A4 may lead to orthostatic hypotension, akathisia, acute dystonia, Parkinsonism, confusion, postural instability or other lurasidone toxicities.(1) PREDISPOSING FACTORS: Elderly patients, particularly those with a history of falls, swallowing disorders, Parkinson Disease, Lewy Body Disease, or other dementias are more sensitive to antipsychotics and have a greater risk for adverse effects.(1) PATIENT MANAGEMENT: The US manufacturer of lurasidone states that concurrent use of a strong CYP3A4 inhibitor is contraindicated.(1) The US Department of Health and Human Services HIV guidelines state that all protease inhibitors boosted with ritonavir or cobicistat are contraindicated.(5) If a patient maintained on lurasidone requires a protease inhibitor for treatment of HIV or hepatitis C, then the patient should be converted to another antipsychotic prior to initiation of protease inhibitor therapy. If a patient is currently on lurasidone and addition of unboosted atazanavir is necessary, the dose of lurasidone should be decreased by 50% of the original dose.(5) If a patient is currently on unboosted atazanavir and lurasidone is added to therapy, the recommended starting dose of lurasidone is 20 mg per day, and the maximum dose is 80 mg daily.(5) DISCUSSION: Pretreatment with ketoconazole (400 mg daily for 5 days), a strong inhibitor of CYP3A4, increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of lurasidone (10 mg) by 6.9-fold, and 9.0-fold, respectively.(1) Pretreatment with diltiazem (240 mg daily for 5 days), a moderate inhibitor of CYP3A4, increased the Cmax and AUC of a single dose of lurasidone (20 mg) by 2.1-fold, and 2.2-fold, respectively.(1) Agents linked to this monograph are atazanavir, boceprevir, cobicistat, darunavir, fosamprenavir, indinavir, lopinavir, nelfinavir, nirmatrelvir, paritaprevir, saquinavir, telaprevir, and tipranavir.	LATUDA, LURASIDONE HCL
Ticagrelor/Strong CYP3A4 Inhibitors; Protease Inhibitors 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: Strong inhibitors of CYP3A4 may inhibit the metabolism of ticagrelor.(1,2) CLINICAL EFFECTS: Concurrent use of a strong inhibitor of CYP3A4 may result in a substantial increase in exposure to and effects from ticagrelor, including increased risk of bleeding.(1,2) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The UK manufacturer of ticagrelor states that concurrent use of strong CYP3A4 inhibitors is contraindicated.(1) The US manufacturer of ticagrelor states that concurrent use of strong CYP3A4 inhibitors should be avoided.(2) The US manufacturer of itraconazole states that concurrent use of ticagrelor is contraindicated during and two weeks after itraconazole treatment.(3) DISCUSSION: Concurrent ketoconazole increased ticagrelor maximum concentration (Cmax) and area-under-curve (AUC) by 2.4-fold and 7.3-fold, respectively. The Cmax and AUC of the active ticagrelor metabolite decreased by 89% and 56%, respectively.(1) Strong CYP3A4 inhibitors linked include: adagrasib, atazanavir, boceprevir, ceritinib, clarithromycin, cobicistat, darunavir, fosamprenavir, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, lonafarnib, lopinavir/ritonavir, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir/ritonavir, posaconazole, ribociclib, saquinavir, telaprevir, telithromycin, tucatinib, and voriconazole.(4,5)	BRILINTA, TICAGRELOR
Atorvastatin (>20 mg)/Selected Protease Inhibitors 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: Protease inhibitors may inhibit the metabolism of atorvastatin by CYP3A4.(1-5) CLINICAL EFFECTS: Concurrent use of protease inhibitors may result in elevated levels of atorvastatin, which could result in rhabdomyolysis.(1-5) PREDISPOSING FACTORS: The risk for myopathy or rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of myopathy or rhabdomyolysis. Patients with a SLCO1B1 polymorphism that leads to decreased function of the hepatic uptake transporter OATP1B1 may have increased statin concentrations and be predisposed to myopathy or rhabdomyolysis. PATIENT MANAGEMENT: In patients receiving protease inhibitors, consider the use of fluvastatin. If atorvastatin is used with concurrent darunavir, fosamprenavir, lopinavir, or saquinavir, limit the dose of atorvastatin to 20 mg daily with careful monitoring.(1-5) DISCUSSION: A study in 15 subjects found that darunavir/ritonavir (300/100 mg twice daily) decreased the maximum concentration (Cmax) and area-under curve (AUC) of atorvastatin (10 mg daily) by 44% and 15%, when compared to atorvastatin (40 mg daily) administered alone. Atorvastatin minimum concentration (Cmin) increased by 81% during concurrent therapy.(2) In a study in 16 subjects, concurrent atorvastatin (10 mg daily for 4 days) and fosamprenavir (1400 mg twice daily for 2 weeks) increased atorvastatin Cmax and AUC by 304% and 130%, respectively. Atorvastatin Cmin decreased by 10%.(3) The Cmax, AUC, and Cmin of amprenavir decreased by by 18%, 27%, and 12%, respectively.(3) In a study in 16 subjects, the administration of atorvastatin (10 mg daily for 4 days) and fosamprenavir (700 mg twice daily for 2 weeks) with ritonavir (100 mg twice daily for 2 weeks) increased the atorvastatin Cmax, AUC, and Cmin by 184%, 153%, and 73%, respectively.(1,4) There were no changes in amprenavir Cmax, AUC, or Cmin.(3) A randomized, controlled trial in healthy subjects examined the effects of a combination of ritonavir and saquinavir on the pharmacokinetics of atorvastatin, pravastatin, and simvastatin and the effects of pravastatin on nelfinavir pharmacokinetics. The combination of ritonavir and saquinavir decreased pravastatin levels by 50% and increased atorvastatin and simvastatin levels by 79% and 3059%, respectively. Pravastatin had no statistically significant effect on nelfinavir pharmacokinetics.(6) Concurrent administration of atorvastatin (40 mg for 4 days) with ritonavir-saquinavir (400 mg twice daily) increased atorvastatin AUC and Cmax by 3.9-fold and 4.3-fold, respectively.(1) Concurrent administration of atorvastatin (20 mg) with lopinavir-ritonavir (400-100 mg twice daily) increased atorvastatin by 5.9-fold.(1)	AMLODIPINE-ATORVASTATIN, ATORVALIQ, ATORVASTATIN CALCIUM, CADUET, LIPITOR
Flibanserin/Strong or Moderate CYP3A4 Inhibitors 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: Flibanserin is primarily metabolized by CYP3A4, though CYP2C19 also plays a role in metabolism.(1) CLINICAL EFFECTS: Concurrent use of a strong or moderate inhibitor of CYP3A4 may result in high to very high levels of and toxicity from flibanserin, including severe hypotension or syncope.(1) PREDISPOSING FACTORS: Patients with any degree of hepatic impairment, who are poor CYP2C19 metabolizers, or who also receive concomitant therapy with strong CYP2C19 inhibitors are expected to have increased systemic concentrations of flibanserin, adding to the risk for hypotension or syncopal episodes.(1) Hypotensive or syncopal episodes are more common when flibanserin is taken during waking hours.(1) PATIENT MANAGEMENT: The concomitant use of flibanserin with moderate or strong CYP3A4 inhibitors significantly increases flibanserin concentrations which may lead to hypotension and syncope. The manufacturer of flibanserin states moderate or strong CYP3A4 inhibitors are contraindicated.(1) If the benefit of initiating a CYP3A4 inhibitor within 2 days of stopping flibanserin clearly outweighs the risk flibanserin-associated hypotension or syncope, monitor and counsel the patient regarding symptoms of hypotension or syncope. Discontinue moderate or strong CYP3A4 inhibitors for 2 weeks before initiating or restarting flibanserin therapy.(1) DISCUSSION: In a drug interaction study with 15 healthy subjects, the combination of flibanserin (100 mg on day 6) and fluconazole (a moderate CYP3A4 and strong CYP2C19 inhibitor, 400 mg once then 200 mg daily for 5 days) resulted in an increased flibanserin exposure of 7-fold. Hypotension or syncope requiring supine placement with leg elevation occurred in 3 subjects (20%). One patient became unresponsive with a blood pressure of 64/41 mm Hg and required emergency room treatment where she required intravenous saline.(1) Though the combination has not been studied, a similar result is plausible with voriconazole, a strong CYP3A4 inhibitor and moderate CYP2C19 inhibitor.(1) In a drug interaction study with flibanserin 50 mg (one-half of the recommended dose) and ketoconazole 400 mg, flibanserin exposure increased 4.5-fold. One of 24 patients(4%) developed syncope.(1) A study of 12 healthy men and women on itraconazole (400 mg once then 200 mg daily for 4 days) with flibanserin 50 mg given 2 hours after itraconazole found that flibanserin exposure was increased 2.6-fold.(1) Strong inhibitors of CYP3A4 include: adagrasib, boceprevir, ceritinib, clarithromycin, cobicistat, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, lonafarnib, lopinavir/ritonavir, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir, posaconazole, ribociclib, saquinavir, telaprevir, telithromycin, tipranavir, troleandomycin, tucatinib, and voriconazole.(1-3) Moderate inhibitors of CYP3A4 include: amprenavir, aprepitant, atazanavir, avacopan, berotralstat, clofazimine, conivaptan, crizotinib, darunavir/ritonavir, diltiazem, dronedarone, duvelisib, erythromycin, fedratinib, fluconazole (also a CYP2C19 inhibitor), fluvoxamine, fosamprenavir, fosnetupitant, imatinib, isavuconazonium, lenacapavir, letermovir, ledipasvir, netupitant, schisandra, nilotinib, treosulfan and verapamil.(1-3)	ADDYI, FLIBANSERIN
Avanafil/Strong CYP3A4 Inhibitors; Atazanavir; Darunavir 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: Inhibitors of CYP3A4 may inhibit the metabolism of avanafil.(1-2) CLINICAL EFFECTS: The concurrent administration of a CYP3A4 inhibitor may result in elevated levels of avanafil, which may result in increased adverse effects such as hypotension, visual changes, and priapism.(1-2) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The US manufacturer of avanafil states that the concurrent use of strong inhibitors of CYP3A4 is contraindicated.(1) The US Department of Health and Human Services HIV guidelines state that boosted atazanavir or darunavir should not be coadministered with avanafil. Unboosted atazanavir may be coadministered with avanafil doses not exceeding 50 mg every 24 hours.(2) The US manufacturer of itraconazole states that concurrent use of avanafil is contraindicated during and two weeks after itraconazole treatment.(3) DISCUSSION: Ketoconazole (400 mg daily), a strong inhibitor of CYP3A4, increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of avanafil (50 mg) by 3-fold and 13-fold, respectively. The half-life of avanafil increased from 5 hours to 9 hours.(1) Ritonavir (600 mg BID), a strong inhibitor of CYP3A4 and an inhibitor of CYP2C19, increased the Cmax and AUC of a single dose of avanafil (50 mg) by 2.4-fold and 13-fold, respectively. The half-life of avanafil increased from 5 hours to 9 hours.(1) Erythromycin (500 mg BID), a moderate inhibitor of CYP3A4, increased the Cmax and AUC of a single dose of avanafil (200 mg) by 2-fold and 3-fold, respectively. The half-life of avanafil increased from 5 hours to 8 hours.(1) Strong inhibitors of CYP3A4 include: adagrasib, boceprevir, ceritinib, clarithromycin, cobicistat, elvitegravir, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, lonafarnib, lopinavir/ritonavir, mibefradil, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir, posaconazole, ribociclib, saquinavir, telaprevir, telithromycin, tipranavir, troleandomycin, tucatinib, and voriconazole.(4-5)	AVANAFIL, STENDRA
Naloxegol (Greater Than 12.5 mg)/Moderate CYP3A4 Inhibitors 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: Inhibitors of CYP3A4 may inhibit the metabolism of naloxegol.(1) CLINICAL EFFECTS: Concurrent use of a moderate inhibitor of CYP3A4 without a dosage adjustment of naloxegol may result in increased levels of naloxegol, which may precipitate opioid withdrawal symptoms.(1) PREDISPOSING FACTORS: Patients taking methadone may be more likely to experience gastrointestinal side effects such as abdominal pain and diarrhea as a result of opioid withdrawal.(1) PATIENT MANAGEMENT: The daily dose of naloxegol should be limited to 12.5 mg daily in patients taking moderate inhibitors of CYP3A4.(1) If concurrent use is deemed medically necessary, monitor patients for signs of opioid withdrawal such as sweating, chills, diarrhea, stomach pain, anxiety, irritability, yawning, restlessness, muscle/joint aches, increased lacrimation, running nose, and piloerection. Monitor patients taking methadone for abdominal pain and diarrhea as well.(1) DISCUSSION: Ketoconazole (400 mg daily for 5 days), a strong inhibitor of CYP3A4, increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of naloxegol by 9.58-fold and 12.85-fold, respectively.(2) Diltiazem (240 mg XR daily), a moderate inhibitor of CYP3A4, increased the Cmax and AUC of a single dose of naloxegol by 2.85 and 3.41, respectively.(2) According to Physiologically-based-Pharmacokinetic (PBPK) models, erythromycin, a moderate inhibitor of CYP3A4, at a dose of 250 mg QID is expected to increase the Cmax and AUC of naloxegol by 2.77-fold and 3.47-fold, respectively.(2) According to PBPK models, erythromycin at a dose of 400 mg QID is expected to increase the Cmax and AUC of naloxegol by 3.42-fold and 4.63-fold, respectively.(2) According to PBPK models, fluconazole, a moderate inhibitor of CYP3A4, at a dose of 200 mg daily is expected to increase the Cmax and AUC of naloxegol by 2.4-fold and 2.81-fold, respectively.(2) According to PBPK models, verapamil moderate inhibitor of CYP3A4, at a dose of 120 mg daily is expected to increase the Cmax and AUC of naloxegol by 1.97-fold and 2.21-fold, respectively.(2) Moderate inhibitors of CYP3A4 include: amprenavir, aprepitant, atazanavir, avacopan, berotralstat, clofazimine, conivaptan, crizotinib, darunavir, diltiazem, dronedarone, duvelisib, erythromycin, fedratinib, fluconazole, fluvoxamine, fosamprenavir, fosnetupitant, imatinib, isavuconazonium, lefamulin, lenacapavir, letermovir, netupitant, nilotinib, nirogacestat, schisandra, tofisopam, treosulfan and verapamil.(1,3,4)	MOVANTIK
Elbasvir-Grazoprevir/OATP1B1-3 Inhibitors 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: Inhibitors of OATP1B1/3 may decrease the hepatocyte uptake and increase the plasma concentrations of elbasvir and grazoprevir.(1-3) CLINICAL EFFECTS: Concurrent use of an inhibitor of OATP1B1/3 may result in elevated levels of grazoprevir and an increased risk of ALT elevations.(1-3) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Concurrent use of elbasvir-grazoprevir and OATP1B1/3 inhibitors is contraindicated.(1-2,4) If concurrent use is deemed medically necessary, monitor the patient for toxicity and elevated AST levels. DISCUSSION: In a study in 10 subjects, atazanavir/ritonavir (300/100 mg daily) increased the maximum concentration (Cmax), area-under-curve (AUC), and minimum concentration (Cmin) of elbasvir (50 mg daily) by 4.15-fold, 4.76-fold, and 6.45-fold, respectively. There were no clinically significant effects on atazanavir levels.(1,2) In a study in 12 subjects, atazanavir/ritonavir (300/100 mg daily) increased the Cmax, AUC, and Cmin of grazoprevir (200 mg daily) by 6.24-fold, 10.58-fold, and 11.64-fold, respectively. There were no clinically significant effects on atazanavir levels.(1,2) In a study in 14 subjects, cyclosporine (400 mg single dose) increased the Cmax, AUC, and Cmin of elbasvir (50 mg daily) by 1.95-fold, 1.98-fold, and 2.21-fold, respectively. The Cmax, AUC, and Cmin of grazoprevir (200 mg daily) increased by 17-fold, 15.21-fold, and 3.39-fold, respectively. There were no clinically significant effects on cyclosporine levels.(1,2) In a study in 10 subjects, darunavir/ritonavir (600/100 mg twice daily) increased the Cmax, AUC, and Cmin of elbasvir (50 mg daily) by 1.67-fold, 1.66-fold, and 1.82-fold, respectively. There were no clinically significant effects on darunavir levels.(1,2) In a study in 13 subjects, darunavir/ritonavir (600/100 mg twice daily) increased the Cmax, AUC, and Cmin of grazoprevir (200 mg daily) by 5.27-fold, 7.50-fold, and 8.05-fold, respectively. There were no clinically significant effects on darunavir levels.(1,2) In a study in 10 subjects, lopinavir/ritonavir (400/100 mg twice daily) increased the Cmax, AUC, and Cmin of elbasvir (50 mg daily) by 2.87-fold, 3.71-fold, and 4.58-fold, respectively. There were no clinically significant effects on lopinavir levels.(1,2) In a study in 13 subjects, lopinavir/ritonavir (400/100 mg twice daily) increased the Cmax, AUC, and Cmin of grazoprevir (200 mg daily) by 7.31-fold, 12.86-fold, and 21.70-fold, respectively. There were no clinically significant effects on lopinavir levels.(1,2) In single dose studies, rifampin increased levels of both elbasvir and grazoprevir. In a study in 14 subjects, rifampin (600 mg single IV dose) increased the Cmax, AUC, and Cmin of a single dose of elbasvir (50 mg) by 41%, 22%, and 31%, respectively. In a study in 14 subjects, rifampin (600 mg single oral dose) increased the Cmax, AUC, and Cmin of a single dose of elbasvir (50 mg) by 29%, 17%, and 21%, respectively. In a study in 12 subjects, rifampin (600 mg single IV dose) increased the Cmax, AUC, and Cmin of a single dose of grazoprevir (200 mg) by 10.94-fold, 10.21-fold, and 1.77-fold, respectively. In a study in 12 subjects, rifampin (600 mg single oral dose) increased the Cmax, AUC, and Cmin of a single dose of grazoprevir (200 mg) by 6.52-fold, 8.35-fold, and 1.61-fold, respectively.(1) OATP1B1/3 inhibitors include asciminib, atazanavir, belumosudil, cyclosporine, darunavir, fostemsavir, letermovir, lopinavir, nirmatrelvir/ritonavir, paritaprevir, resmetirom, roxadustat, saquinavir, tipranavir, vadadustat, and voclosporin.(1-3)	ZEPATIER
Lomitapide/Strong or Moderate CYP3A4 Inhibitors 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: Lomitapide is primarily metabolized via CYP3A4.(1) CLINICAL EFFECTS: Concurrent use of a strong or moderate inhibitor of CYP3A4 may result in high to very high levels of and toxicity from lomitapide.(1) PREDISPOSING FACTORS: The interaction may be more severe in patients with hepatic impairment or with end-stage renal disease.(1) PATIENT MANAGEMENT: Given the magnitude of this interaction and the potential toxicity of lomitapide, moderate and strong CYP3A4 inhibitors are contraindicated.(1) When possible use an alternative to the CYP3A4 inhibitor. If a moderate or strong CYP3A4 inhibitor is required, discontinue lomitapide. Due to its long half-life, it will take 1 to 2 weeks for remaining lomitapide to be eliminated; thus lomitapide adverse effects could occur after discontinuation. The US manufacturer of itraconazole states that concurrent use with lomitapide is contraindicated during and two weeks after itraconazole treatment.(4) DISCUSSION: Concurrent administration with ketoconazole (a strong inhibitor of CYP3A4) increased lomitapide area-under-curve (AUC) by 27-fold.(1) Strong inhibitors of CYP3A4 include: adagrasib, boceprevir, ceritinib, clarithromycin, cobicistat, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, lonafarnib, lopinavir/ritonavir, mibefradil, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir, posaconazole, ribociclib, saquinavir, telaprevir, telithromycin, tipranavir, tucatinib, and voriconazole.(1-3,5) Moderate inhibitors of CYP3A4 include: amprenavir, aprepitant, atazanavir, avacopan, berotralstat, clofazimine, conivaptan, crizotinib, darunavir/ritonavir, diltiazem, dronedarone, duvelisib, erythromycin, fedratinib, fluconazole (also a CYP2C19 inhibitor), fluvoxamine, fosamprenavir, fosnetupitant, imatinib, isavuconazonium, lenacapavir, lefamulin, letermovir, netupitant, nilotinib, nirogacestat, schisandra, treosulfan and verapamil.(1-3)	JUXTAPID
Cilostazol (Greater than 50 mg BID)/Selected Strong & Moderate CYP3A4 Inhibitors 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: Strong and moderate inhibitors of CYP3A4 may inhibit the metabolism of cilostazol.(1) CLINICAL EFFECTS: The concurrent use of cilostazol and strong and moderate inhibitors of CYP3A4 may result in elevated levels of cilostazol, which may produce increased effects of cilostazol and adverse effects.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The dose of cilostazol should be limited to 50 mg twice daily in patients receiving concurrent therapy with strong and moderate inhibitors of CYP3A4.(1) DISCUSSION: In a study in 16 healthy males, the administration of a single dose of cilostazol (10 mg) with erythromycin (500 mg every eight hours) increased the maximum concentration (Cmax) and area-under-curve (AUC) of cilostazol by 47% and 73%, respectively. The Cmax and AUC of 4'-trans-hydroxy-cilostazol were increased by 29% and 141%, respectively.(2) Analysis of population pharmacokinetics indicated that the concurrent administration of diltiazem with cilostazol increased cilostazol concentrations by 53%. Concurrent administration of diltiazem and cilostazol decreased cilostazol clearance by 30%, increased the Cmax by 30%, and increased AUC by 40%.(1) In a study, the administration of a single dose of cilostazol (10 mg) with erythromycin (500 mg every eight hours) increased the Cmax and AUC of cilostazol by 47% and 73%, respectively. The AUC of 4'-trans-hydroxy-cilostazol was increased by 141%.(1) In an vitro study in human liver microsomes, ketoconazole inhibited the metabolism of cilostazol.(3)	CILOSTAZOL
Lumateperone (>10.5 mg)/Strong CYP3A4 Inhib; Protease Inhib 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: Strong inhibitors of CYP3A4 and protease inhibitors may inhibit the metabolism of lumateperone.(1,2) CLINICAL EFFECTS: Concurrent use of lumateperone with strong CYP3A4 inhibitors or protease inhibitors increases lumateperone exposure, which may increase the risk of adverse reactions.(1,2) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The manufacturer of lumateperone recommends decreasing the dosage of lumateperone to 10.5 mg once daily in patients receiving strong CYP3A4 inhibitors.(1) The US Department of Health and Human Services HIV guidelines state that protease inhibitors should not be coadministered with lumateperone.(2) DISCUSSION: Coadministration of lumateperone with itraconazole, a strong CYP3A4 inhibitor, resulted in a 4-fold and 3.5-fold increase in area-under-curve (AUC) and concentration maximum (Cmax), respectively.(1) Coadministration of lumateperone with diltiazem, a moderate CYP3A4 inhibitor, resulted in a 2.5-fold and 2-fold increase AUC and Cmax, respectively.(1) Strong inhibitors of CYP3A4 include: adagrasib, amprenavir, atazanavir, boceprevir, ceritinib, clarithromycin, cobicistat, darunavir, fosamprenavir, grapefruit, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, levoketoconazole, lonafarnib, lopinavir/ritonavir, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir, posaconazole, ribociclib, saquinavir, telaprevir, telithromycin, tipranavir, troleandomycin, tucatinib, and voriconazole.(2-4)	CAPLYTA
Protease Inhibitors/Apalutamide 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: Apalutamide is a strong inducer of CYP3A4 and is expected to increase the metabolism of the HIV protease inhibitors.(1-5) HIV protease inhibitors are moderate to strong inhibitors of CYP3A4 and may decrease the metabolism of apalutamide.(1-5) CLINICAL EFFECTS: The net effect of the opposing effects of apalutamide and the protease inhibitors on CYP3A4 is unknown. Concurrent or recent use of apalutamide with a protease inhibitor may result in decreased levels and effectiveness of the protease inhibitor. Virologic failure and drug resistance may occur.(1-3) Alternatively, protease inhibitors may increase the plasma concentration and toxicities of apalutamide.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The manufacturer of lopinavir-ritonavir and of ritonavir states that concurrent use with apalutamide is contraindicated due to the risk of virologic failure and development of drug resistance.(2,3) Since the other protease inhibitors are also CYP3A4 substrates and frequently used with ritonavir, they are included in this monograph. If alternatives are not available and concurrent use is deemed medically necessary, follow HIV viral loads closely. DISCUSSION: Co-administration of apalutamide with a single dose of midazolam (a CYP3A4 substrate) led to a 92 % decrease in the area-under-curve (AUC) of midazolam.(1) Ketoconazole, a strong CYP3A4 inhibitor, was predicted to increase the AUC of single-dose apalutamide by 24% and of steady-state apalutamide by 51%.(1)	ERLEADA
Mitapivat (Greater Than 20 mg)/Moderate CYP3A4 Inhibitors 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: Moderate inhibitors of CYP3A4 may inhibit the metabolism of mitapivat.(1) CLINICAL EFFECTS: Concurrent use of a moderate inhibitor of CYP3A4 may result in increased levels of and effects from mitapivat including decreased estrone and estradiol levels in males, increased urate, back pain, and arthralgias.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The concurrent use of moderate CYP3A4 inhibitors with mitapivat should be monitored closely for increased risk of adverse reactions. Mitapivat dose should not exceed 20 mg twice daily with concurrent moderate CYP3A4 inhibitors.(1) DISCUSSION: Mitapivat is a CYP3A4 substrate. In a pharmacokinetic study with mitapivat 5, 20, or 50 mg twice daily dosing, fluconazole increased mitapivat area-under-curve (AUC) and concentration maximum (Cmax) by 2.6-fold and 1.6-fold, respectively.(1) Moderate inhibitors of CYP3A4 include: amprenavir, aprepitant, atazanavir, berotralstat, clofazimine, conivaptan, darunavir, diltiazem, dronedarone, erythromycin, fluconazole, fluvoxamine, fosamprenavir, fosnetupitant, imatinib, isavuconazonium, letermovir, netupitant, nilotinib, schisandra, treosulfan and verapamil.(2)(2)	PYRUKYND
Pimavanserin (Greater Than 10 mg)/Strong CYP3A4 Inhibitors; Protease Inhibitors 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: Agents which inhibit the CYP3A4 enzyme may inhibit the metabolism of pimavanserin.(1) CLINICAL EFFECTS: Concurrent use of strong CYP3A4 inhibitors or HIV protease inhibitors may increase systemic exposure and the risk for pimavanserin toxicities such as peripheral edema, confusion, or QT prolongation.(1,2) PREDISPOSING FACTORS: The risk of QT prolongation or torsade de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsade de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(3) 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 torsade 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).(3) PATIENT MANAGEMENT: When concomitant use of pimavanserin and a strong CYP3A4 inhibitor or HIV protease inhibitor is needed, the pimavanserin dose should be reduced to 10 mg once daily.(1,2) With unboosted atazanavir, consider using alternative antipsychotic agents.(2) During concomitant therapy with a strong CYP3A4 inhibitor or HIV protease inhibitor, monitor patients closely for prolongation of the QT interval. Obtain serum calcium, magnesium, and potassium levels and monitor ECG at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting. DISCUSSION: In a drug interaction study, ketoconazole increased pimavanserin maximum concentration (Cmax) 1.5-fold and area-under-curve(AUC) 3-fold. A thorough QTc study performed in 252 subjects found a mean maximum change from baseline of 13.5 msec (upper bound of the 90% confidence interval was 16.6 msec) at twice the therapeutic dose.(1) Thus, coadministration of pimavanserin and a QT prolonging agent, even at a reduced dose, may increase the risk for significant QT prolongation. CYP3A4 inhibitors linked to this monograph include: atazanavir, boceprevir, cobicistat, darunavir, fosamprenavir, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir/ritonavir, paritaprevir, telaprevir, tipranavir, troleandomycin, and tucatinib.(4)	NUPLAZID
Daridorexant (Greater Than 25 mg)/Moderate CYP3A4 Inhibitors 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: Moderate inhibitors of CYP3A4 may inhibit the metabolism of daridorexant.(1) CLINICAL EFFECTS: Concurrent use of a moderate inhibitor of CYP3A4 may result in increased levels of and effects from daridorexant including somnolence, fatigue, CNS depressant effects, daytime impairment, or headache.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The dose of daridorexant should be limited to 25 mg daily when used with a moderate CYP3A4 inhibitor.(1) DISCUSSION: Daridorexant is a CYP3A4 substrate. In a PKPB model, concurrent use of daridorexant with diltiazem, a moderate CYP3A4 inhibitor, increased daridorexant area-under-curve (AUC) and maximum concentration (Cmax) by 2.4-fold and 1.4-fold, respectively.(1) Moderate CYP3A4 inhibitors include: amprenavir, aprepitant, atazanavir, avacopan, berotralstat, clofazimine, conivaptan, crizotinib, darunavir, diltiazem, dronedarone, duvelisib, erythromycin, fedratinib, fluconazole, fluvoxamine, fosamprenavir, fosnetupitant, imatinib, isavuconazonium, lenacapavir, letermovir, netupitant, nilotinib, nirogacestat, schisandra, treosulfan and verapamil.(2)	QUVIVIQ
Colchicine (for Cardioprotection)/Strong CYP3A4 Inhibitors;Atazanavir;Darunavir 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: Strong CYP3A4 inhibitors may inhibit the metabolism of colchicine.(1,2) CLINICAL EFFECTS: Concurrent use of a strong CYP3A4 inhibitor may result in elevated levels of and toxicity from colchicine. Symptoms of colchicine toxicity include muscle weakness or pain; numbness or tingling in the fingers or toes; myelosuppression; abdominal pain; nausea; severe diarrhea or vomiting; feeling weak or tired; increased infections; and pale or gray color of the lips, tongue, or palms of hands.(1,2) PREDISPOSING FACTORS: This interaction is expected to be more severe in patients with renal or hepatic impairment.(1,2) PATIENT MANAGEMENT: The manufacturer of colchicine used for cardiovascular risk reduction states that concurrent use of colchicine with strong CYP3A4 inhibitors is contraindicated.(1) DISCUSSION: There are several reports of colchicine toxicity(4-6) and death(7,8) following the addition of clarithromycin to therapy. In a retrospective review of 116 patients who received clarithromycin and colchicine during the same hospitalization, 10.2% (9/88) of patients who received simultaneous therapy died, compared to 3.6% (1/28) of patients who received sequential therapy.(9) An FDA review of 117 colchicine-related deaths that were not attributable to overdose found that 60 deaths (51%) involved concurrent use of clarithromycin.(2) In a study in 23 subjects, pretreatment with clarithromycin (250 mg twice daily for 7 days) increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of colchicine (0.6 mg) by 227.2% (range 65.7% to 591.1%) and by 281.5% (range 88.7% to 851.6%), respectively.(1) In a study in 24 subjects, pretreatment with ketoconazole (200 mg twice daily for 5 days) increased the Cmax and AUC of a single dose of colchicine (0.6 mg) by 101.7% (range 19.6% to 219%) and by 212.2% (range 76.7% to 419.6%), respectively.(1) In a study in 18 subjects, pretreatment with ritonavir (100 mg twice daily for 5 days) increased the Cmax and AUC of a single dose of colchicine (0.6 mg) by 184.4% (range 79.2% to 447.4%) and by 296% (range 53.8% to 924.4%), respectively.(1) Colchicine toxicity has been reported with concurrent use of CYP3A4 and P-gp inhibitors such as clarithromycin, cyclosporine, diltiazem, erythromycin, and verapamil.(1,2) Strong inhibitors of CYP3A4 include: adagrasib, atazanavir, boceprevir, ceritinib, clarithromycin, cobicistat, darunavir, idelalisib, indinavir, itraconazole, josamycin, ketoconazole, levoketoconazole, lonafarnib, lopinavir/ritonavir, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir, paritaprevir, posaconazole, ribociclib, saquinavir, telaprevir, telithromycin, tipranavir, troleandomycin, tucatinib, and voriconazole.(1,10)	LODOCO

Drug contraindication overview.

*Concomitant use of ritonavir-boosted darunavir or cobicistat-boosted darunavir with drugs highly dependent on cytochrome P-450 (CYP) isoenzyme CYP3A for metabolism and for which elevated plasma concentrations are associated with serious and/or life-threatening events. *Concomitant use of cobicistat-boosted darunavir with drugs that are CYP3A inducers which may lead to lower darunavir and cobicistat exposures and potential loss of efficacy and the development of resistance. *Examples of drugs contraindicated for administration with ritonavir-boosted darunavir or cobicistat-boosted darunavir include: alfuzosin, carbamazepine, phenobarbital, phenytoin, colchicine in patients with renal or hepatic impairment, rifampin, lurasidone, pimozide, dronedarone, ivabradine, ranolazine, dihydroergotamine (DHE), ergotamine, methylergonovine, St. John's wort (Hypericum perforatum), the fixed combination of elbasvir and grazoprevir (elbasvir/grazoprevir), lomitapide, lovastatin, simvastatin, naloxegol, orally administered midazolam and triazolam, and sildenafil (Revatio(R)) for treatment of pulmonary arterial hypertension.

Adverse reaction overview.

Adverse effects of at least moderate intensity (greater than or equal to Grade 2) reported in more than 5% of patients receiving ritonavir-boosted or cobicistat-boosted darunavir in conjunction with other antiretrovirals are diarrhea, nausea, vomiting, abdominal pain, headache, and rash.

Darunavir is not recommended in pediatric patients younger than 3 years of age since toxicity and mortality have been observed in juvenile rats given darunavir. Safety, pharmacokinetic profile, and efficacy of ritonavir-boosted darunavir have been evaluated in antiretroviral-naive and antiretroviral-experienced pediatric patients 3 years to less than 18 years of age weighing at least 10 kg. Adverse effects reported in pediatric patients were similar to those reported in adults.

Safety and efficacy of cobicistat-boosted darunavir was established in pediatric patients weighing at least 40 kg. Use of cobicistat-boosted darunavir in this patient group is supported by evidence from studies in adults, with additional pharmacokinetic, safety, and virologic data from a study of the components of Prezcobix(R) in pediatric subjects 12 to less than 18 years of age.

Contraindicated

None

Severe Precaution

None

Management or Monitoring Precaution

None