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Drug overview for UNITHROID (levothyroxine sodium):
Generic name: LEVOTHYROXINE SODIUM (lee-voe-thye-ROX-een)
Drug class: Thyroid Hormones
Therapeutic class: Endocrine
Levothyroxine sodium, the sodium salt of the l-isomer of thyroxine, is a thyroid agent.
No enhanced Uses information available for this drug.
Generic name: LEVOTHYROXINE SODIUM (lee-voe-thye-ROX-een)
Drug class: Thyroid Hormones
Therapeutic class: Endocrine
Levothyroxine sodium, the sodium salt of the l-isomer of thyroxine, is a thyroid agent.
No enhanced Uses information available for this drug.
DRUG IMAGES
LEVOTHYROXINE 25 MCG TABLET
The following indications for UNITHROID (levothyroxine sodium) have been approved by the FDA:
Indications:
Adjunct to surgery or radiotherapy for thyroid carcinoma
Hypothyroidism
Professional Synonyms:
None.
Indications:
Adjunct to surgery or radiotherapy for thyroid carcinoma
Hypothyroidism
Professional Synonyms:
None.
The following dosing information is available for UNITHROID (levothyroxine sodium):
The FDA states that all approved levothyroxine sodium preparations should be considered therapeutically inequivalent unless equivalence has been established and noted in FDA's Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book). Theoretically, such preparations can be used interchangeably, and in some cases, pharmacists may be able to substitute generic for proprietary (brand) preparations without notifying the prescriber. However, because of the narrow therapeutic index of the drug, the American Thyroid Association (ATA) and the American Association of Clinical Endocrinologists (AACE) state that levothyroxine sodium preparations generally should not be used interchangeably.
If a patient switches levothyroxine sodium preparations (e.g., from brand to generic), pharmacists are encouraged to notify the patient and prescriber of the switch. In addition, serum thyrotropin (thyroid-stimulating hormone, TSH) concentration should be measured about 4-8 weeks after starting the new preparation and the levothyroxine dosage adjusted if needed.
Dosage of levothyroxine sodium must be carefully adjusted according to individual requirements and response. The age, body weight, and general physical condition of the patient and the severity and duration of hypothyroid symptoms determine the initial dosage and rate at which dosage may be increased to the eventual maintenance dosage. Under- or over-treatment, which may result in adverse effects on growth and development in pediatric patients, cardiovascular function, bone metabolism, reproductive function, cognitive function, emotional state, GI function, and glucose and lipid metabolism, should be avoided.
Dosage should be initiated at a lower level in geriatric patients, in patients with functional or ECG evidence of cardiovascular disease, and in patients with severe, long-standing hypothyroidism, since an abrupt increase in metabolic rate and demand for increased cardiac output associated with levothyroxine therapy may precipitate angina pectoris, myocardial infarction, congestive heart failure, arrhythmias, or sudden cardiac death in such patients. In patients with severe, long-standing hypothyroidism in whom pituitary and adrenal function may be secondarily decreased, rapid replacement therapy with levothyroxine sodium also may precipitate adrenal insufficiency; in addition, psychosis or agitation occasionally may develop during initiation of levothyroxine therapy, necessitating a lower initial dosage in these patients. Adjustment of thyroid replacement therapy should be determined mainly by the patient's clinical response and confirmed by appropriate laboratory tests.
The manufacturer of levothyroxine sodium for injection states that caution should be used when switching patients from oral to IV levothyroxine sodium since the relative bioavailability and an accurate dosing conversion between the oral and IV preparations have not been established. Relative bioavailability between oral and IV administration has been estimated to range from 48-74%.
For the management of hypothyroidism in otherwise healthy individuals younger than 50 years of age and in those older than 50 years of age who have been recently treated for hyperthyroidism or who have been hypothyroid for only a short time (i.e., several months), the usual initial oral dosage (full replacement dosage) of levothyroxine sodium is 1.7 mcg/kg daily (e.g., 100-125 mcg daily for a 70-kg adult) given as a single dose. Older patients may require less than 1 mcg/kg daily.
In one study, the usual maintenance dosage for geriatric patients was about 25% less than that for younger and heavier adults. Some manufacturers state that levothyroxine sodium dosages greater than 200 mcg daily are seldom required, and that failure to respond adequately to oral dosages of 300 mcg daily or greater is rare and should prompt reevaluation of the diagnosis, or suggest the presence of malabsorption, patient noncompliance, and/or drug interactions.
Patients should be evaluated initially about every 6-8 weeks to monitor the response to therapy. Once normalization of thyroid function and serum thyrotropin (thyroid-stimulating hormone, TSH) concentrations has been achieved, patients may be evaluated less frequently (i.e., every 6-12 months). However, if the dosage of levothyroxine sodium tablets is changed, serum TSH concentrations should be measured after 8-12 weeks or 4-8 weeks after switching from one levothyroxine sodium preparation to another.
For most patients older than 50 years of age or in patients younger than 50 years of age with underlying cardiovascular disease, the usual initial oral dosage of levothyroxine sodium is 25-50 mcg daily given as a single dose; dosage may be increased at intervals of 6-8 weeks. The usual initial dosage in geriatric patients with underlying cardiovascular disease is 12.5-25 mcg daily, with gradual dosage increments at intervals of 4-6 weeks.
Dosage may be increased by increments of 12.5-25 mcg at recommended intervals until the patient becomes euthyroid and serum TSH concentrations return to normal.
For the management of severe, long-standing hypothyroidism in adults, the usual initial oral dosage of levothyroxine sodium is 12.5-25 mcg daily given as a single dose. Although the manufacturers state that dosage may be increased by increments of 25 mcg at intervals of 2-4 weeks until serum TSH concentrations return to normal, some clinicians suggest that dosage may be adjusted at intervals of 4-8 weeks.
If treatment is considered necessary in patients with subclinical hypothyroidism, the manufacturers state that lower initial levothyroxine dosages (e.g., 1 mcg/kg daily) may be adequate to normalize TSH concentrations. If levothyroxine replacement therapy is not initiated, patients still should be monitored annually for changes in clinical status and thyroid laboratory parameters.
Although the average full replacement dosage of levothyroxine sodium is about 1.6-1.7 mcg/kg daily, some patients (e.g., younger pediatric patients, pregnant women) may require higher dosages.
Despite the smaller body size of pediatric patients, the dosage of levothyroxine sodium (on a weight basis) required to sustain a full rate of growth, development, and general thriving is higher in these patients than in adults. In general, levothyroxine sodium therapy should be initiated at full replacement dosages in pediatric patients as soon as possible after diagnosis of hypothyroidism to prevent deleterious effects on intellectual and physical growth and development; however, dosage should be initiated at a lower level in children with long-standing or severe hypothyroidism.
For the treatment of congenital hypothyroidism (cretinism) or acquired hypothyroidism in pediatric patients, levothyroxine sodium therapy usually is initiated at full replacement dosages; daily dose per body weight decreases with age. The following dosages have been recommended:
Age Daily Dose 0-3 months 10-15 mcg/kg 3-6 months 25-50 mcg or 8-10 mcg/kg 6-12 months 50-75 mcg or 6-8 mcg/kg 1-5 years 75-100 mcg or 5-6 mcg/kg 6-12 years 100-150 mcg or 4-5 mcg/kg Older than 12 years > 150 mcg or 2-3 mcg/kg Growth and puberty complete 1.6-1.7 mcg/kg
The usual initial oral dosage of levothyroxine sodium in otherwise healthy, full-term neonates is 10-15 mcg/kg daily given as a single dose. A lower initial dosage (e.g., 25 mcg daily) should be considered in neonates at risk of cardiac failure; dosage may be increased at intervals of 4-6 weeks as needed based on clinical and laboratory response to treatment. In neonates with very low (less than 5 mcg/dL) or undetectable serum thyroxine (T4) concentrations, the usual initial dosage is 50 mcg daily.
The manufacturers state that hyperactivity in an older child may be minimized by initiating therapy at a dosage approximately one-fourth of the recommended full replacement dosage; the dosage may then be increased by an amount equal to one-fourth the full recommended replacement dosage at weekly intervals until the full recommended replacement dosage is reached.
For the treatment of severe, long-standing hypothyroidism in pediatric patients, the usual initial oral dosage of levothyroxine sodium is 25 mcg daily. Dosage may be increased in increments of 25 mcg at intervals of 2-4 weeks until the desired response is obtained.
If a patient switches levothyroxine sodium preparations (e.g., from brand to generic), pharmacists are encouraged to notify the patient and prescriber of the switch. In addition, serum thyrotropin (thyroid-stimulating hormone, TSH) concentration should be measured about 4-8 weeks after starting the new preparation and the levothyroxine dosage adjusted if needed.
Dosage of levothyroxine sodium must be carefully adjusted according to individual requirements and response. The age, body weight, and general physical condition of the patient and the severity and duration of hypothyroid symptoms determine the initial dosage and rate at which dosage may be increased to the eventual maintenance dosage. Under- or over-treatment, which may result in adverse effects on growth and development in pediatric patients, cardiovascular function, bone metabolism, reproductive function, cognitive function, emotional state, GI function, and glucose and lipid metabolism, should be avoided.
Dosage should be initiated at a lower level in geriatric patients, in patients with functional or ECG evidence of cardiovascular disease, and in patients with severe, long-standing hypothyroidism, since an abrupt increase in metabolic rate and demand for increased cardiac output associated with levothyroxine therapy may precipitate angina pectoris, myocardial infarction, congestive heart failure, arrhythmias, or sudden cardiac death in such patients. In patients with severe, long-standing hypothyroidism in whom pituitary and adrenal function may be secondarily decreased, rapid replacement therapy with levothyroxine sodium also may precipitate adrenal insufficiency; in addition, psychosis or agitation occasionally may develop during initiation of levothyroxine therapy, necessitating a lower initial dosage in these patients. Adjustment of thyroid replacement therapy should be determined mainly by the patient's clinical response and confirmed by appropriate laboratory tests.
The manufacturer of levothyroxine sodium for injection states that caution should be used when switching patients from oral to IV levothyroxine sodium since the relative bioavailability and an accurate dosing conversion between the oral and IV preparations have not been established. Relative bioavailability between oral and IV administration has been estimated to range from 48-74%.
For the management of hypothyroidism in otherwise healthy individuals younger than 50 years of age and in those older than 50 years of age who have been recently treated for hyperthyroidism or who have been hypothyroid for only a short time (i.e., several months), the usual initial oral dosage (full replacement dosage) of levothyroxine sodium is 1.7 mcg/kg daily (e.g., 100-125 mcg daily for a 70-kg adult) given as a single dose. Older patients may require less than 1 mcg/kg daily.
In one study, the usual maintenance dosage for geriatric patients was about 25% less than that for younger and heavier adults. Some manufacturers state that levothyroxine sodium dosages greater than 200 mcg daily are seldom required, and that failure to respond adequately to oral dosages of 300 mcg daily or greater is rare and should prompt reevaluation of the diagnosis, or suggest the presence of malabsorption, patient noncompliance, and/or drug interactions.
Patients should be evaluated initially about every 6-8 weeks to monitor the response to therapy. Once normalization of thyroid function and serum thyrotropin (thyroid-stimulating hormone, TSH) concentrations has been achieved, patients may be evaluated less frequently (i.e., every 6-12 months). However, if the dosage of levothyroxine sodium tablets is changed, serum TSH concentrations should be measured after 8-12 weeks or 4-8 weeks after switching from one levothyroxine sodium preparation to another.
For most patients older than 50 years of age or in patients younger than 50 years of age with underlying cardiovascular disease, the usual initial oral dosage of levothyroxine sodium is 25-50 mcg daily given as a single dose; dosage may be increased at intervals of 6-8 weeks. The usual initial dosage in geriatric patients with underlying cardiovascular disease is 12.5-25 mcg daily, with gradual dosage increments at intervals of 4-6 weeks.
Dosage may be increased by increments of 12.5-25 mcg at recommended intervals until the patient becomes euthyroid and serum TSH concentrations return to normal.
For the management of severe, long-standing hypothyroidism in adults, the usual initial oral dosage of levothyroxine sodium is 12.5-25 mcg daily given as a single dose. Although the manufacturers state that dosage may be increased by increments of 25 mcg at intervals of 2-4 weeks until serum TSH concentrations return to normal, some clinicians suggest that dosage may be adjusted at intervals of 4-8 weeks.
If treatment is considered necessary in patients with subclinical hypothyroidism, the manufacturers state that lower initial levothyroxine dosages (e.g., 1 mcg/kg daily) may be adequate to normalize TSH concentrations. If levothyroxine replacement therapy is not initiated, patients still should be monitored annually for changes in clinical status and thyroid laboratory parameters.
Although the average full replacement dosage of levothyroxine sodium is about 1.6-1.7 mcg/kg daily, some patients (e.g., younger pediatric patients, pregnant women) may require higher dosages.
Despite the smaller body size of pediatric patients, the dosage of levothyroxine sodium (on a weight basis) required to sustain a full rate of growth, development, and general thriving is higher in these patients than in adults. In general, levothyroxine sodium therapy should be initiated at full replacement dosages in pediatric patients as soon as possible after diagnosis of hypothyroidism to prevent deleterious effects on intellectual and physical growth and development; however, dosage should be initiated at a lower level in children with long-standing or severe hypothyroidism.
For the treatment of congenital hypothyroidism (cretinism) or acquired hypothyroidism in pediatric patients, levothyroxine sodium therapy usually is initiated at full replacement dosages; daily dose per body weight decreases with age. The following dosages have been recommended:
Age Daily Dose 0-3 months 10-15 mcg/kg 3-6 months 25-50 mcg or 8-10 mcg/kg 6-12 months 50-75 mcg or 6-8 mcg/kg 1-5 years 75-100 mcg or 5-6 mcg/kg 6-12 years 100-150 mcg or 4-5 mcg/kg Older than 12 years > 150 mcg or 2-3 mcg/kg Growth and puberty complete 1.6-1.7 mcg/kg
The usual initial oral dosage of levothyroxine sodium in otherwise healthy, full-term neonates is 10-15 mcg/kg daily given as a single dose. A lower initial dosage (e.g., 25 mcg daily) should be considered in neonates at risk of cardiac failure; dosage may be increased at intervals of 4-6 weeks as needed based on clinical and laboratory response to treatment. In neonates with very low (less than 5 mcg/dL) or undetectable serum thyroxine (T4) concentrations, the usual initial dosage is 50 mcg daily.
The manufacturers state that hyperactivity in an older child may be minimized by initiating therapy at a dosage approximately one-fourth of the recommended full replacement dosage; the dosage may then be increased by an amount equal to one-fourth the full recommended replacement dosage at weekly intervals until the full recommended replacement dosage is reached.
For the treatment of severe, long-standing hypothyroidism in pediatric patients, the usual initial oral dosage of levothyroxine sodium is 25 mcg daily. Dosage may be increased in increments of 25 mcg at intervals of 2-4 weeks until the desired response is obtained.
No enhanced Administration information available for this drug.
| DRUG LABEL | DOSING TYPE | DOSING INSTRUCTIONS |
|---|---|---|
| LEVOTHYROXINE 25 MCG TABLET | Maintenance | Adults take 1 tablet (25 mcg) by oral route once daily |
| DRUG LABEL | DOSING TYPE | DOSING INSTRUCTIONS |
|---|---|---|
| LEVOTHYROXINE 25 MCG TABLET | Maintenance | Adults take 1 tablet (25 mcg) by oral route once daily |
The following drug interaction information is available for UNITHROID (levothyroxine sodium):
There are 0 contraindications.
There are 2 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 |
|---|---|
| Radioactive Iodide/Agents that Affect Iodide SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction. MECHANISM OF ACTION: Many compounds can affect iodide protein binding and alter iodide pharmacokinetics and pharmacodynamics.(1) CLINICAL EFFECTS: Compounds that affect iodide pharmacokinetics and pharmacodynamics may impact the effectiveness of radioactive iodide.(1) PREDISPOSING FACTORS: Compounds that affect iodide pharmacokinetics and pharmacodynamics are expected to have the most impact during therapy using radioactive iodide. Diagnostic procedures would be expected to be impacted less. PATIENT MANAGEMENT: Discuss the use of agents that affect iodide pharmacokinetics and pharmacodynamics with the patient's oncologist.(1) Because indocyanine green contains sodium iodide, the iodine-binding capacity of thyroid tissue may be reduced for at least one week following administration. Do not perform radioactive iodine uptake studies for at least one week following administration of indocyanine green.(2) The manufacturer of iopamidol states administration may interfere with thyroid uptake of radioactive iodine and decrease therapeutic and diagnostic efficacy. Avoid thyroid therapy or testing for up to 6 weeks post administration of iopamidol.(3) DISCUSSION: Many agents interact with radioactive iodine. The average duration of effect is: anticoagulants - 1 week antihistamines - 1 week anti-thyroid drugs, e.g: carbimazole, methimazole, propylthiouracil - 3-5 days corticosteroids - 1 week iodide-containing medications, e.g: amiodarone - 1-6 months expectorants - 2 weeks Lugol solution - 3 weeks saturated solution of potassium iodine - 3 weeks vitamins - 10-14 days iodide-containing X-ray contrast agents - up to 1 year lithium - 4 weeks phenylbutazone - 1-2 weeks sulfonamides - 1 week thyroid hormones (natural or synthetic), e.g.: thyroxine - 4 weeks tri-iodothyronine - 2 weeks tolbutamide - 1 week topical iodide - 1-9 months (1) |
ADREVIEW, JEANATOPE, MEGATOPE, SODIUM IODIDE I-123 |
| Sodium Iodide I 131/Agents that Affect Iodide SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction. MECHANISM OF ACTION: Many compounds can affect iodide protein binding and alter iodide pharmacokinetics and pharmacodynamics.(1,2) CLINICAL EFFECTS: Compounds that affect iodide pharmacokinetics and pharmacodynamics may impact the effectiveness of radioactive iodide.(1,2) PREDISPOSING FACTORS: Compounds that affect iodide pharmacokinetics and pharmacodynamics are expected to have the most impact during therapy using radioactive iodide. Diagnostic procedures would be expected to be impacted less. PATIENT MANAGEMENT: Discuss the use of agents that affect iodide pharmacokinetics and pharmacodynamics with the patient's oncologist.(1,2) Because indocyanine green contains sodium iodide, the iodine-binding capacity of thyroid tissue may be reduced for at least one week following administration. Do not perform radioactive iodine uptake studies for at least one week following administration of indocyanine green.(3) The manufacturer of iopamidol states administration may interfere with thyroid uptake of radioactive iodine and decrease therapeutic and diagnostic efficacy. Avoid thyroid therapy or testing for up to 6 weeks post administration of iopamidol.(4) DISCUSSION: Many agents interact with radioactive iodine. The average duration of effect is: anticoagulants - 1 week antihistamines - 1 week anti-thyroid drugs, e.g: carbimazole, methimazole, propylthiouracil - 3-5 days corticosteroids - 1 week iodide-containing medications, e.g: amiodarone - 1-6 months expectorants - 2 weeks Lugol solution - 3 weeks saturated solution of potassium iodine - 3 weeks vitamins - 10-14 days iodide-containing X-ray contrast agents - up to 1 year lithium - 4 weeks phenylbutazone - 1-2 weeks sulfonamides - 1 week thyroid hormones (natural or synthetic), e.g.: thyroxine - 4 weeks tri-iodothyronine - 2 weeks tolbutamide - 1 week topical iodide - 1-9 months (1,2) |
HICON, SODIUM IODIDE I-131 |
There are 13 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 |
|---|---|
| Thyroid Preps/Bile Acid Sequestrants; Lanthanum; Sevelamer SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Bile acid sequestrants, lanthanum and sevelamer may decrease the gastrointestinal absorption of thyroid drugs.(1) CLINICAL EFFECTS: Simultaneous administration of a bile acid sequestrant, lanthanum or sevelamer may result in decreased absorption and effectiveness of thyroid drugs.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: For maximal bioavailability, thyroid preparations should be taken on an empty stomach at least 4 hours apart from bile acid sequestrants and sevelamer.(1-3) Thyroid preparations should be taken at least 2 hours apart from lanthanum.(4) DISCUSSION: The effect of cholestyramine on the absorption of thyroid drugs appears to be clinically significant, resulting in approximately a 50% decrease in thyroid absorption. Cholestyramine has been used to treat thyroid overdoses. When administered with colesevelam (3.75 g), the area-under-curve (AUC) and maximum concentration (Cmax) of levothyroxine (600 mcg) decreased by 22% and by 33%, respectively. When administered 1 hour prior to colesevelam, the AUC of levothyroxine increased by 6% and the Cmax of levothyroxine decreased by 2%, respectively. When administered 4 hours prior to colesevelam, the AUC and Cmax of levothyroxine increased by 1% and 8%, respectively. Although used for hyperphosphatemia, sevelamer is linked to this monograph due to its structural and pharmacologic similarities to colesevelam. Both agents are non-absorbed cross linked polymers with a high affinity for bile acids.(2,3) An in vivo study in healthy subjects evaluated the bioavailability of levothyroxine 1 mg when given with or without sevelamer 800 mg. Concomitant administration of sevelamer decreased levothyroxine AUC by 46%.(13) One case report described a newly diagnosed hypothyroid patient with a TSH of 297 mU/L (reference 0.03 - 4.20 mU/L). She took her daily levothyroxine with her morning blood pressure medications, acetaminophen, B-vitamins and sevelamer 3200 mg. Over 3 months of treatment her levothyroxine dose was increased to 150 mcg daily but the TSH remained high at 196 mU/L. Her levothyroxine dose was changed to an evening dose taken at least 4 hours after medications. Three weeks later she was symptomatically improved and TSH had decreased to 19 mU/L. She was inadvertently rechallenged on the morning levothyroxine and sevelamer regimen due to a hospitalization. After the hospital stay her TSH risen to 76 mU/L; on return to her evening regimen her TSH again normalized.(14) |
CHOLESTYRAMINE, CHOLESTYRAMINE LIGHT, CHOLESTYRAMINE RESIN, COLESEVELAM HCL, COLESTID, COLESTIPOL HCL, FOSRENOL, LANTHANUM CARBONATE, PREVALITE, QUESTRAN, QUESTRAN LIGHT, RENVELA, SEVELAMER CARBONATE, SEVELAMER HCL, WELCHOL |
| Thyroid Preparations/Calcium; Iron; Sucralfate SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: The mechanism by which malabsorption of thyroid preparations occurs from calcium-containing products is presumed to be a binding of the medication to the thyroid hormone, forming an insoluble or nonabsorbable complex.(1-3) Iron may form a ferric-thyroxine complex with thyroid agents, preventing their absorption from the gastrointestinal tract.(1,4) Sucralfate binds to other agents in the gastrointestinal tract and alters absorption of other drugs, including thyroid agents.(1,5) CLINICAL EFFECTS: The simultaneous administration of thyroid preparations with calcium, iron, or sucralfate may result in decreased levels and clinical effects of thyroid preparations.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Instruct patients to separate the administration time of thyroid preparations from calcium or iron by as much time as possible, preferably by at least four hours.(1) Administer thyroid preparations at least 2 hours before sucralfate.(5) Patients taking thyroid preparations and calcium- or iron-containing products or sucralfate should be monitored for changes in thyroid function. The dosage of the thyroid preparation may need to be increased. Separating the administration times of the thyroid preparation and the calcium- or iron-containing products or sucralfate may decrease the effects of the interaction.(1-5) DISCUSSION: In a pharmacokinetic study 8 healthy, euthyroid adults were given levothyroxine alone and levothyroxine coadministered with calcium carbonate, calcium citrate, or calcium acetate in doses containing 500 mg elemental calcium. The coadministration of each of the three calcium preparations significantly reduced levothyroxine absorption by about 20%-25% compared with levothyroxine given alone.(3) In a study in 14 subjects, the simultaneous administration of thyroxine with ferrous sulfate for 12 weeks resulted in an increase in the mean level of thyroid stimulating hormone (TSH) from 1.6+/-0.4 mU/L to 5.4+/-2.8 mU/L. Mixing thyroxine with ferrous sulfate in vitro resulted in a poorly soluble complex.(4) In a study in 20 hypothyroid patients, the simultaneous administration of levothyroxine and calcium carbonate (1200 mg) daily for three months resulted in reductions in the mean free T4 and total T4 levels. These values increased in most patients following the discontinuation of calcium carbonate. A concurrent in-vitro study found that calcium carbonate adsorbed levothyroxine in solution at a pH of 2, gastric pH, but not at a pH of 7.4.(6) One author reported three cases of decreased levothyroxine efficacy following the addition of calcium carbonate to therapy.(7) In a study in 5 healthy subjects, levothyroxine (five 200 mcg tablets) was administered in 3 different dosing regimens: after an overnight fast, with the fifth and final dose of sucralfate (1 gram every 6 hours) and 8 hours after the second and final dose of sucralfate (2 grams every 12 hours). When administered alone, 80% of levothyroxine was absorbed within 6 hours of administration, compared to 23% when administered concurrently with sucralfate. There was no difference in levothyroxine absorption when administered alone or 8 hours after sucralfate.(8) There are several case reports documenting decreased effects of thyroid supplementation as the result of simultaneous administration of sucralfate.(9,10) One or more of the drug pairs linked to this monograph have been included in a list of interactions that could be considered for classification as "non-interruptive" 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. |
ACCRUFER, AUROVELA 24 FE, AUROVELA FE, AURYXIA, BALCOLTRA, BLISOVI 24 FE, BLISOVI FE, CALCIUM ACETATE, CALCIUM CHLORIDE, CALCIUM GLUCONATE, CALCIUM GLUCONATE MONOHYDRATE, CARAFATE, CHARLOTTE 24 FE, FEIRZA, FERRIC CITRATE, FINZALA, GEMMILY, HAILEY 24 FE, HAILEY FE, JOYEAUX, JUNEL FE, JUNEL FE 24, KAITLIB FE, LARIN 24 FE, LARIN FE, LAYOLIS FE, LEVONORG-ETH ESTRAD-FE BISGLYC, LO LOESTRIN FE, LOESTRIN FE, MERZEE, MIBELAS 24 FE, MICROGESTIN FE, MINZOYA, NORETHIN-ETH ESTRA-FERROUS FUM, NORETHINDRONE-E.ESTRADIOL-IRON, SUCRALFATE, TARINA 24 FE, TARINA FE, TARINA FE 1-20 EQ, TAYTULLA, TILIA FE, TRI-LEGEST FE, VELPHORO, WYMZYA FE, XARAH FE, XELRIA FE |
| Thyroid Preparations/Polystyrene Sulfonate SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Polystyrene sulfonate may bind and delay or prevent the absorption of thyroid preparations from the gastrointestinal tract.(1) CLINICAL EFFECTS: Simultaneous administration of polystyrene sulfonate may result in decreased levels of and effectiveness from thyroid preparations.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The US manufacturer of levothyroxine states that levothyroxine should be administered at least 4 hours apart from polystyrene sulfonate.(1) DISCUSSION: Because polystyrene sulfonate may bind and delay or prevent the absorption of levothyroxine from the gastrointestinal tract, the US manufacturer of levothyroxine states that levothyroxine should be administered at least 4 hours apart from polystyrene sulfonate.(1) |
KIONEX, SODIUM POLYSTYRENE SULFONATE, SPS |
| Thyroid Preparations/Orlistat SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Orlistat may bind to the thyroid preparation in the small intestine, decreasing systemic absorption.(1-4) CLINICAL EFFECTS: Concurrent administration of orlistat and thyroid preparations may decrease the clinical effects of the thyroid agent.(1-4) Hypothyroidism has been reported.(3) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Separate the administration times of orlistat and thyroid preparations by at least 4 hours. Patients receiving concurrent therapy should be monitored for changes in thyroid function.(1-3) DISCUSSION: In a case report, a post-thyroidectomy patient on a stable dose of levothyroxine (250 mcg daily) started concurrent orlistat therapy. Within two weeks of starting orlistat therapy, she felt experienced cold intolerance and felt lethargic and tired. She was found be severely hypothyroid and the orlistat was discontinued. Within two weeks, her symptoms improved and, within 4 weeks, her thyroid levels normalized.(4) |
ORLISTAT, XENICAL |
| Thyroid Preparations/Ciprofloxacin SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Ciprofloxacin may inhibit organic anion transporting polypeptide (OATP) 1A2 in the intestines, either through competitive or direct inhibition.(1) CLINICAL EFFECTS: The simultaneous administration of thyroid preparations and ciprofloxacin may result in decreased levels and clinical effects of thyroid hormones.(1) PREDISPOSING FACTORS: This interaction may be more significant in patients receiving long term courses of ciprofloxacin. PATIENT MANAGEMENT: Patients taking thyroid preparations and ciprofloxacin should be monitored for changes in thyroid function. Separating the administration times of the thyroid preparation and ciprofloxacin by 6 hours, may decrease the effects of the interaction.(1,2) DISCUSSION: In a study, 8 healthy individuals received single doses of levothyroxine (100 mcg) combined with placebo or ciprofloxacin (750 mg). The simultaneous administration of ciprofloxacin significantly decreased the T4 AUC by 39% (p=0.035). The reduction in T4 AUC after coadministration of ciprofloxacin with levothyroxine is consistent with inhibition of an intestinal T4 uptake transport.(1) In a case report, two patients with hypothyroidism and receiving levothyroxine developed decreased T4 levels after taking ciprofloxacin for 3-4 weeks.(2) |
CIPRO, CIPROFLOXACIN, CIPROFLOXACIN HCL |
| Thyroid Preparations/Imatinib;Sunitinib SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: The suspected mechanism responsible for this phenomenon is an induction of non-deiodination clearance. The induction of uridine diphosphate-glucuronyl transferases (UGTs) by imatinib and sunitinib decreases levels of the thyroid preparations.(1) CLINICAL EFFECTS: The coadministration of thyroid preparations and imatinib and sunitinib may result in decreased levels and clinical effects of thyroid hormones.(1-3) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Patients taking thyroid preparations and imatinib or sunitinib should be monitored for changes in thyroid function. The dosage of the thyroid preparation may need to be increased.(1-3) DISCUSSION: In a case report, 8 patients had undergone thyroidectomy and used levothyroxine and imatinib. These patients had an increase need for levothyroxine levels and were monitored for elevations in thyrotropin indicating worsening hypothyroidism.(2) A case report of a 73 year old man who was treated with imatinib and levothyroxine developed worsening hypothyroidism. An increase in levothyroxine dosage was needed.(3) In a case report, a 59 year old woman was taking levothyroxine therapy for hypothyroidism secondary to subtotal thyroidectomy and was recently started on imatinib for chronic myeloid leukemia. The patient developed clinical signs of hypothyroidism and required an increased dose of levothyroxine.(4) In a case report, a 73 year old woman was taking levothyroxine and developed fatigue, nausea, cold-intolerance, hair-loss, brittle nails, progressive weakness, and impressive facial oedema 6 months after starting imatinib. The patient levothyroxine was increased and she remained euthyroid, but the imatinib was discontinued due to extreme fatigue and periorbital oedema. Five months later the patient was stared on sunitinib and her levothyroxine dose was increased. The patient developed similar symptoms to imatinib reaction.(5) In a case report, a patient receiving sunitinib for metastatic papillary renal cell cancer developed high thyroid stimulating hormone levels and severe symptoms despite receiving L-thyroxine.(6) |
GLEEVEC, IMATINIB MESYLATE, IMKELDI, SUNITINIB MALATE, SUTENT |
| Thyroid Preparations/Rifampin SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Rifampin is an organic anion transporting polypeptide (OATP) inhibitor and has been found to decrease measured free T4 when taking thyroid replacements. The mechanism for the rifampin effect may be due to induction of hepatic metabolic and biliary clearance. It is also possible that rifampin may have increased net intestinal absorption of L-T4 through inhibition of P-glycoprotein, an intestinal efflux transporter. CLINICAL EFFECTS: The concurrent or recent use of rifampin may result in altered levels and clinical effects of thyroid hormones. Some patients may experience increased thyroid hormone effects, while others may experience decreased effects.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Patients taking thyroid preparations and rifampin should be monitored for changes in thyroid function. Symptoms of hyperthyroidism include weight loss, rapid heartbeat, nervousness, sweating, tremor, fatigue, and difficulty sleeping. Symptoms of hypothyroidism include fatigue, sluggishness, constipation, stiffness, muscle cramps, loss of appetite, excessive weight gain, or dry skin. The dosage of levothyroxine may need to be adjusted accordingly. DISCUSSION: In a study, 8 healthy individuals received 100 mcg of levothyroxine combined with placebo or rifampin 600 mg. The coadministration of rifampin significantly increased the 4 AUC by 25% (p=0.003). Levothyroxine absorptions with rifampin was 125% compared to controls.(1) In contrast to this study, two case reports exist documenting decreased effects of levothyroxine during concurrent rifampin. In a case report, a 31 year old woman had a total thyroidectomy and was receiving levothyroxine and was recently started on rifampin. The patient did not develop symptoms of hypothyroidism, but had a decrease in serum thyroxine levels and free thyroxine index during rifampin therapy and an increase in serum thyrotropin levels.(2) In a case report of a 50 year old male, stable on levothyroxine, who exhibited significantly elevated TSH levels during therapy with rifampin. The patient's TSH levels returned to baseline 9 days after discontinuing rifampin.(3) |
RIFADIN, RIFAMPIN |
| Patiromer/Thyroid Preparations SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Patiromer may bind to thyroid preparations.(1) CLINICAL EFFECTS: Concurrent use may result in decreased gastrointestinal absorption and loss of efficacy of the thyroid preparation.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: The US manufacturer of patiromer recommends that you administer patiromer at least 3 hours before or 3 hours after levothyroxine.(1) DISCUSSION: A study in healthy volunteers showed that patiromer decreased the systemic exposure of coadministered levothyroxine. No interaction was seen when these drugs were taken 3 hours apart.(1) |
VELTASSA |
| Thyroid Preparations/Ritonavir SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Thyroid preparations are substrates for uridine diphosphate glucuronosyltransferase (UGT). Also, levothyroxine is converted to the thyroid hormone triiodothyronine (T3) which is further metabolized via UGT.(1) Ritonavir may induce UGT and may increase metabolism of levothyroxine and T3.(1) CLINICAL EFFECTS: The concurrent use of ritonavir may result in decreased levels and clinical effects of the thyroid preparation. PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Patients taking thyroid preparations and ritonavir should be monitored for changes in thyroid function. Symptoms of hypothyroidism include fatigue, sluggishness, constipation, stiffness, muscle cramps, loss of appetite, excessive weight gain, or dry skin. The dosage of the thyroid preparation may need to be adjusted accordingly. DISCUSSION: A case report of a 29 year old male with auto-immune thyroiditis was stabilized on levothyroxine 125 mcg daily for one year when concurrent therapy with stavudine 40 mg twice daily, lamivudine 150 mg twice daily, ritonavir 600 mg twice daily, and saquinavir 400 mg twice daily was started. One month after concurrent therapy, the patient's thyroid stimulating hormone (TSH) increased to 18.47 mIU/L (a 2.7-fold increase) requiring a dose increase of levothyroxine to 250 mcg daily. Subsequently, ritonavir was discontinued with a decrease in levothyroxine dose to 125 mcg daily with stabilization of TSH at 7.32 mIU/L.(2) A case report of a 58 year old female on zidovudine, lamivudine, and lopinavir/ritonavir underwent a total thyroidectomy with subsequent introduction of levothyroxine. Levothyroxine was titrated to 225 mcg daily along with the addition of liothyronine. Due to persistently elevated TSH values (range 47.6 - 85.1 mIU/L), lopinavir/ritonavir was then withdrawn and two months later TSH and T4 levels returned to normal, 4.1 mIU/L and 12.1 pmol/L, respectively. Eight months later lopinavir/ritonavir was reintroduced and 1 month later TSH and T4 increased to 42.9 mIU/L and 10.6 mIU/L, respectively. Again, lopinavir/ritonavir was withdrawn and TSH and T4 values returned to normal, 1.1 mIU/L and 13.4 pmol/L, respectively.(3) A case report of a 37 year old female on abacavir/lamivudine and lopinavir/ritonavir details the management course of hypothyroidism over a six year period, including during 3 pregnancies. After a total thyroidectomy, the patient was started on levothyroxine 75 mcg daily. Post-surgical levels of TSH and T4 (during patient's second pregnancy) increased to 94.3 mIU/L and 6.1 mIU/L, respectively, and peaked at 125.89 mIU/L and 7.7 mIU/L, respectively. Levothyroxine doses were increased to 175 mcg daily over the following year (during the patient's second and third pregnancies) to achieve decreased TSH and T4 values of 8.58 mIU/L and 12.8 mIU/L, respectively. TSH values rose again to 17.23 mIU/L and ritonavir was withdrawn from therapy. The patient was then maintained on levothyroxine 125 mcg daily with a TSH of 0.12 - 0.42 mIU/L over the next 2 years.(1) |
KALETRA, LOPINAVIR-RITONAVIR, NORVIR, RITONAVIR |
| Thyroid Preparations/Sertraline SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: The mechanism by which sertraline lowers serum thyroid hormone concentrations is uncertain. One reported case in which sertraline caused a low serum total thyroxine concentration is believed to be caused by sertraline increasing the clearance of the thyroxine.(1) CLINICAL EFFECTS: The coadministration of thyroid preparations and sertraline may result in decreased levels and clinical effects of thyroid hormones.(1) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Patients taking thyroid preparations and sertraline should be monitored for changes in thyroid function. The dosage of the thyroid preparation may need to be increased. DISCUSSION: In a case report of 9 levothyroxine treated patients with hypothyroidism, who were treated with sertraline, all were found to have elevated serum thyrotropin concentrations. Elevated thyrotropin levels are indicative of a decrease in the efficacy of levothyroxine. The dose of levothyroxine was increased for all patients. Required dosage adjustments ranged from 11% to 50%.(1) In a study, patients with major depression and hypothyroidism on adequate levothyroxine therapy were treated with either fluoxetine or sertraline. The results of this study showed no change in thyroid levels among hypothyroid patients on levothyroxine therapy who were treated with either fluoxetine or sertraline.(2) |
SERTRALINE HCL, ZOLOFT |
| Thyroid Preparations/Estrogens SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Estrogens increase thyroxine-binding globulin (TBG) levels by increasing its biosynthesis and decreasing its clearance.(1) Hypothyroid patients who start estrogens may be unable to compensate for this increase and may have decreased serum free T4 (FT4) concentrations and increased TSH.(1,2) CLINICAL EFFECTS: The coadministration of thyroid preparations and estrogens may result in decreased levels and clinical effects of thyroid hormones.(1-4) PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Patients taking thyroid preparations and who start or stop estrogens should be monitored for changes in thyroid function. The dosage of the thyroid preparation may need to be increased.(1-4) DISCUSSION: In a prospective observational study, 25 post-menopausal women with hypothyroidism on stable levothyroxine therapy for at least 9 months started on estrogen replacement therapy. After 12 weeks, mean serum FT4 levels decreased significantly from 1.7 +/- 0.4 ng/dL to 1.4 +/-0.3 mg/dL and TSH increased significantly from 0.9 +/-1.1 to 3.2 +/- 3.1 milli-units/L.(1) |
2-METHOXYESTRADIOL, ACTIVELLA, AFIRMELLE, ALTAVERA, ALYACEN, AMETHIA, AMETHYST, ANGELIQ, ANNOVERA, APRI, ARANELLE, ASHLYNA, AUBRA, AUBRA EQ, AUROVELA, AUROVELA 24 FE, AUROVELA FE, AVIANE, AYUNA, AZURETTE, BALCOLTRA, BALZIVA, BEYAZ, BIJUVA, BLISOVI 24 FE, BLISOVI FE, BRIELLYN, CAMRESE, CAMRESE LO, CAZIANT, CHARLOTTE 24 FE, CHATEAL EQ, CLIMARA, CLIMARA PRO, COMBIPATCH, COVARYX, COVARYX H.S., CRYSELLE, CYRED, CYRED EQ, DASETTA, DAYSEE, DELESTROGEN, DEPO-ESTRADIOL, DESOGESTR-ETH ESTRAD ETH ESTRA, DIETHYLSTILBESTROL, DIVIGEL, DOLISHALE, DOTTI, DROSPIRENONE-ETH ESTRA-LEVOMEF, DROSPIRENONE-ETHINYL ESTRADIOL, DUAVEE, EEMT, EEMT H.S., ELESTRIN, ELINEST, ELURYNG, ENILLORING, ENPRESSE, ENSKYCE, ESTARYLLA, ESTRACE, ESTRADIOL, ESTRADIOL (ONCE WEEKLY), ESTRADIOL (TWICE WEEKLY), ESTRADIOL BENZOATE, ESTRADIOL CYPIONATE, ESTRADIOL HEMIHYDRATE, ESTRADIOL HEMIHYDRATE MICRO, ESTRADIOL MICRONIZED, ESTRADIOL VALERATE, ESTRADIOL-NORETHINDRONE ACETAT, ESTRATEST F.S., ESTRATEST H.S., ESTRING, ESTRIOL, ESTRIOL MICRONIZED, ESTROGEL, ESTROGEN-METHYLTESTOSTERONE, ESTRONE, ETHINYL ESTRADIOL, ETHYNODIOL-ETHINYL ESTRADIOL, ETONOGESTREL-ETHINYL ESTRADIOL, EVAMIST, FALMINA, FEIRZA, FEMLYV, FEMRING, FINZALA, FYAVOLV, GEMMILY, HAILEY, HAILEY 24 FE, HAILEY FE, HALOETTE, ICLEVIA, IMVEXXY, ISIBLOOM, JAIMIESS, JASMIEL, JINTELI, JOLESSA, JOYEAUX, JULEBER, JUNEL, JUNEL FE, JUNEL FE 24, KAITLIB FE, KALLIGA, KARIVA, KELNOR 1-35, KELNOR 1-50, KURVELO, LARIN, LARIN 24 FE, LARIN FE, LAYOLIS FE, LEENA, LESSINA, LEVONEST, LEVONORG-ETH ESTRAD ETH ESTRAD, LEVONORG-ETH ESTRAD-FE BISGLYC, LEVONORGESTREL-ETH ESTRADIOL, LEVORA-28, LO LOESTRIN FE, LO-ZUMANDIMINE, LOESTRIN, LOESTRIN FE, LOJAIMIESS, LORYNA, LOW-OGESTREL, LUTERA, LYLLANA, MARLISSA, MENEST, MENOSTAR, MERZEE, MIBELAS 24 FE, MICROGESTIN, MICROGESTIN FE, MILI, MIMVEY, MINIVELLE, MINZOYA, MONO-LINYAH, MYFEMBREE, NATAZIA, NECON, NEXTSTELLIS, NIKKI, NORELGESTROMIN-ETH ESTRADIOL, NORETHIN-ETH ESTRA-FERROUS FUM, NORETHINDRON-ETHINYL ESTRADIOL, NORETHINDRONE-E.ESTRADIOL-IRON, NORGESTIMATE-ETHINYL ESTRADIOL, NORTREL, NUVARING, NYLIA, OCELLA, ORIAHNN, ORTHO TRI-CYCLEN, ORTHO-NOVUM, PHILITH, PIMTREA, PORTIA, PREMARIN, PREMPHASE, PREMPRO, RECLIPSEN, RIVELSA, SAFYRAL, SETLAKIN, SIMLIYA, SIMPESSE, SPRINTEC, SRONYX, SYEDA, TARINA 24 FE, TARINA FE, TARINA FE 1-20 EQ, TAYTULLA, TILIA FE, TRI-ESTARYLLA, TRI-LEGEST FE, TRI-LINYAH, TRI-LO-ESTARYLLA, TRI-LO-MARZIA, TRI-LO-MILI, TRI-LO-SPRINTEC, TRI-MILI, TRI-SPRINTEC, TRI-VYLIBRA, TRI-VYLIBRA LO, TRIVORA-28, TURQOZ, TWIRLA, TYBLUME, VAGIFEM, VALTYA, VELIVET, VESTURA, VIENVA, VIORELE, VIVELLE-DOT, VOLNEA, VYFEMLA, VYLIBRA, WERA, WYMZYA FE, XARAH FE, XELRIA FE, XULANE, YASMIN 28, YAZ, YUVAFEM, ZAFEMY, ZARAH, ZOVIA 1-35, ZUMANDIMINE |
| Carbimazole; Methimazole/Thyroid Preparations SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Methimazole can affect the therapeutic response to thyroid hormone therapy. It decreases thyroid hormone secretion. Thyroid hormone therapy can antagonize the pharmacologic effects of methimazole by supplying an exogenous source of thyroid hormone. Carbimazole is a prodrug of methimazole.(1) CLINICAL EFFECTS: Concurrent use of carbimazole or methimazole and thyroid hormones may result in opposing effects. PREDISPOSING FACTORS: None determined. PATIENT MANAGEMENT: Concurrent use of carbimazole or methimazole and thyroid hormones should be avoided. DISCUSSION: The 2016 American Thyroid Association guidelines recommended avoiding the concurrent use of methimazole and thyroid preparations for "block and replace" therapy to make a patient euthyroid. Meta-analyses have shown that a higher prevalence of adverse events occurs with block-and-replace regimens than dose titration.(2) The 2018 European Thyroid Association guidelines state that methimazole (30 mg) may be given combined with levothyroxine supplement ion for block-and-replace therapy to avoid drug-induced hypothyroidism but methimazole dose titration is the preferred therapy.(3) |
CARBIMAZOLE, METHIMAZOLE |
| Selected Anticoagulants/Thyroid SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed. MECHANISM OF ACTION: Unknown. However, thyroid hormones may influence concentrations of vitamin K-dependent clotting factors. CLINICAL EFFECTS: Concurrent use of vitamin K antagonists and thyroid hormones may increase the risk for bleeding. Hypothyroidism may increase the oral anticoagulant requirements. Administration of thyroid hormones or hyperthyroidism may decrease oral anticoagulant requirements. 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: Monitor prothrombin activity and adjust the anticoagulant dosage accordingly during initiation of warfarin therapy in patients receiving thyroid replacement therapy, during the initiation or titration of thyroid replacement therapy in patients receiving warfarin, or if any changes in thyroid function occur. 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. 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: Any change in thyroid status in patients stabilized on warfarin may necessitate a change in warfarin dosage requirements. Initiation of thyroid replacement therapy in patients stabilized on warfarin may result in increases in the effects of warfarin. A decrease in the dose of warfarin usually becomes necessary within one to four weeks after starting therapy with thyroid compounds. Warfarin therapy should be initiated in low doses in patients who are hyperthyroid. In a 16 year population based nested matched case control study, 10,532 hospitalizations for hemorrhage were evaluated and matched to 40,595 controls. The primary analysis showed no increase in risk of hemorrhage in older patients on warfarin initiated on levothyroxine in previous 30 days (OR 1.11, 95% CI 0.67-1.86). When patients were matched up to 90 days prior to the hemorrhage event, there was no significant association with levothyroxine 31-60 days prior to index date (OR 0.75 95% CI 0.26-2.25) or 61-90 days prior to index date (OR 0.67 95% CI 0.15-3.01). A retrospective, self-controlled study of 102 patients on chronic warfarin therapy were included if the patient had INR results 90 days before and after starting levothyroxine. The mean warfarin dose/INR ratio in the pre-period and post-period had no significant change (p=0.825). In patients who achieved euthyroid during post-period, warfarin dose/INR ratio was numerically lower in the post-period but not statistically significant (13.42 versus 12.7, respectively; p=0.338). In patients initiated on levothyroxine doses greater than 50 mcg, pre-period and post-period warfarin dose/INR ratio also had no significant difference (p>0.2). |
ANISINDIONE, DICUMAROL, JANTOVEN, PHENINDIONE, WARFARIN SODIUM |
The following contraindication information is available for UNITHROID (levothyroxine sodium):
Drug contraindication overview.
No enhanced Contraindications information available for this drug.
No enhanced Contraindications information available for this drug.
There are 0 contraindications.
There are 2 severe contraindications.
Adequate patient monitoring is recommended for safer drug use.
| Severe List |
|---|
| Myocarditis |
| Primary adrenocortical insufficiency |
There are 4 moderate contraindications.
Clinically significant contraindication, where the condition can be managed or treated before the drug may be given safely.
| Moderate List |
|---|
| Coronary artery disease |
| Diabetes mellitus |
| Osteopenia |
| Osteoporosis |
The following adverse reaction information is available for UNITHROID (levothyroxine sodium):
Adverse reaction overview.
No enhanced Common Adverse Effects information available for this drug.
No enhanced Common Adverse Effects information available for this drug.
There are 15 severe adverse reactions.
| More Frequent | Less Frequent |
|---|---|
| None. |
Osteopenia |
| Rare/Very Rare |
|---|
|
Abnormal hepatic function tests Acute myocardial infarction Angina Angioedema Cardiac arrest Cardiac arrhythmia Dyspnea Heart failure Idiopathic intracranial hypertension Mood changes Seizure disorder Skin rash Tachycardia Urticaria |
There are 26 less severe adverse reactions.
| More Frequent | Less Frequent |
|---|---|
|
Female infertility |
Hypertension Weight loss |
| Rare/Very Rare |
|---|
|
Abdominal pain with cramps Alopecia Chest pain Diarrhea Fatigue Fever Flushing Headache disorder Heat intolerance Hyperhidrosis Increased appetite Increased pulse rate Insomnia Irregular menstrual periods Irritability Menstrual disorder Muscle spasm Muscle weakness Nervousness Palpitations Symptoms of anxiety Tremor Vomiting |
The following precautions are available for UNITHROID (levothyroxine sodium):
No enhanced Pediatric Use information available for this drug.
Contraindicated
Severe Precaution
Management or Monitoring Precaution
Contraindicated
| None |
Severe Precaution
| None |
Management or Monitoring Precaution
| None |
No enhanced Pregnancy information available for this drug.
No enhanced Lactation information available for this drug.
No enhanced Geriatric Use information available for this drug.
The following prioritized warning is available for UNITHROID (levothyroxine sodium):
WARNING: This medication should not be used for weight loss. Normal doses of this medication will not work for weight loss, and large doses of this medication may cause serious, possibly fatal side effects, especially when taken with diet pills.
WARNING: This medication should not be used for weight loss. Normal doses of this medication will not work for weight loss, and large doses of this medication may cause serious, possibly fatal side effects, especially when taken with diet pills.
The following icd codes are available for UNITHROID (levothyroxine sodium)'s list of indications:
| Adjunct to surgery or radiotherapy for thyroid carcinoma | |
| C73 | Malignant neoplasm of thyroid gland |
| Hypothyroidism | |
| E03 | Other hypothyroidism |
| E03.0 | Congenital hypothyroidism with diffuse goiter |
| E03.1 | Congenital hypothyroidism without goiter |
| E03.2 | Hypothyroidism due to medicaments and other exogenous substances |
| E03.3 | Postinfectious hypothyroidism |
| E03.4 | Atrophy of thyroid (acquired) |
| E03.8 | Other specified hypothyroidism |
| E03.9 | Hypothyroidism, unspecified |
| E89.0 | Postprocedural hypothyroidism |
Formulary Reference Tool