Levothyroxine interactions

Clomiphene citrate tablets are contraindicated in patients with uncontrolled thyroid or adrenal dysfunction or in the presence of an organic intracranial lesion such as pituitary tumor (see INDICATIONS AND USAGE). (Clomiphene label, Contraindications)

When concomitant administration of corticosteroids and levothyroxine is required, administration of corticosteroid should precede the initiation of levothyroxine therapy to avoid adrenal crisis. (Dexamethasone label, Warnings and precautions)

Patients suspected of developing thyrotoxicosis should be managed carefully to avoid abrupt withdrawal of beta-adrenergic blocking agents that might precipitate a thyroid storm. (Dorzolamide and timolol label, Warnings and precautions)

WARNING: RISK OF THYROID C-CELL TUMORS In male and female rats, dulaglutide causes a dose-related and treatment-duration-dependent increase in the incidence of thyroid C-cell tumors (adenomas and carcinomas) after lifetime exposure. (Dulaglutide label, Boxed warning)

WARNING: RISK OF THYROID C-CELL TUMORS • Liraglutide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures in both genders of rats and mice. (Liraglutide label, Boxed warning)

Patients suspected of developing thyrotoxicosis should be managed carefully to avoid abrupt withdrawal of beta-adrenergic blockade which might precipitate a thyroid storm. (Nadolol label, Warnings)

Patients suspected of developing thyrotoxicosis should be managed carefully to avoid abrupt withdrawal of beta-blockade which might precipitate a thyroid crisis. (Pindolol label, Warnings)

Avoid abrupt withdrawal of beta-blockade, which may precipitate a thyroid storm. (Propranolol label, Warnings and precautions)

WARNING: RISK OF THYROID C-CELL TUMORS • In rodents, semaglutide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures. (Semaglutide label, Boxed warning)

Thyroid Abnormalities Avoid abrupt withdrawal of beta-blockade which might be followed by an exacerbation of symptoms of hyperthyroidism, including thyroid storm. (Sotalol label, Warnings and precautions)

Patients suspected of developing thyrotoxicosis should be managed carefully to avoid abrupt withdrawal of beta-adrenergic blocking agents that might precipitate a thyroid storm. (Timolol label, Warnings and precautions)

WARNING: RISK OF THYROID C-CELL TUMORS In rats, tirzepatide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures. (Tirzepatide label, Boxed warning)

People who have thyroid problems (hyperthyroidism) may have a higher chance of having a hypertensive crisis. (Tranylcypromine label, Boxed warning)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Levothyroxine The bioavailability of alendronate was slightly decreased when BINOSTO and levothyroxine were co-administered to healthy subjects [see Clinical Pharmacology (12.3) ] . (Alendronate label, Drug interactions)

Other drugs: Amiodarone Amiodarone inhibits peripheral conversion of levothyroxine (T4) to triiodothyronine (T3) and may cause isolated biochemical changes (increase in serum free-T4, and decreased or normal free-T3) in clinically euthyroid patients. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

An initial increase in serum FT 4 is followed by return of FT 4 to normal levels with sustained therapeutic serum salicylate concentrations, although total T 4 levels may decrease by as much as 30%. (Levothyroxine label, Drug interactions)

An initial increase in serum FT 4 is followed by return of FT 4 to normal levels with sustained therapeutic serum salicylate concentrations, although total T 4 levels may decrease by as much as 30%. (Levothyroxine label, Drug interactions)

Drug or Drug Class Effect Beta-adrenergic antagonists e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. (Levothyroxine label, Drug interactions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

An initial increase in serum FT 4 is followed by return of FT 4 to normal levels with sustained therapeutic serum salicylate concentrations, although total T 4 levels may decrease by as much as 30%. (Levothyroxine label, Drug interactions)

Drug or Drug Class Effect Beta-adrenergic antagonists e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. (Levothyroxine label, Drug interactions)

Drug or Drug Class Effect Beta-adrenergic antagonists e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. (Levothyroxine label, Drug interactions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Calcium supplements can reduce absorption of these medicines; take them several hours apart. (NIH Office of Dietary Supplements, Calcium)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total and free T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. (Levothyroxine label, Drug interactions)

Drug or Drug Class Effect Beta-adrenergic antagonists e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. (Levothyroxine label, Drug interactions)

Drug Interactions Cholestyramine for Oral Suspension USP may delay or reduce the absorption of concomitant oral medication such as phenylbutazone, warfarin, thiazide diuretics (acidic), or propranolol (basic), as well as tetracycline, penicillin G, phenobarbital, thyroid and thyroxine preparations, estrogens and progestins, and digitalis. (Cholestyramine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Concomitant use with colesevelam hydrochloride may decrease the exposure of the following drugs: Drugs with a narrow therapeutic index (e.g., cyclosporine), phenytoin, thyroid hormone replacement therapy, warfarin, oral contraceptives containing ethinyl estradiol and norethindrone, olmesartan medoxomil, and sulfonylureas (glimepiride, glipizide, glyburide). (Colesevelam label, Drug interactions)

…1: Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. (Levothyroxine label, Drug interactions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Digitalis Glycosides Levothyroxine may reduce the therapeutic effects of digitalis glycosides. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

…1: Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. (Levothyroxine label, Drug interactions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Abnormal Thyroid Function Tests Dose-dependent decreases in serum T3 and T4 (free and total) values have been observed in patients taking APTIOM. (Eslicarbazepine label, Warnings and precautions)

Drug or Drug Class Effect Beta-adrenergic antagonists e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. (Levothyroxine label, Drug interactions)

…1: Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Furosemide has been shown to inhibit the protein binding of T4 to TBG and albumin, causing an increase free T4 fraction in serum. (Levothyroxine label, Drug interactions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. (Levothyroxine label, Drug interactions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Thyroid function should be monitored periodically. (Interferon beta-1a label, Warnings and precautions)

Iron reduces the absorption of these medicines; take them a few hours apart. (NIH Office of Dietary Supplements, Iron)

Drug or Drug Class Effect Beta-adrenergic antagonists e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

…Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

…1: Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Other drugs: Amiodarone Amiodarone inhibits peripheral conversion of levothyroxine (T4) to triiodothyronine (T3) and may cause isolated biochemical changes (increase in serum free-T4, and decreased or normal free-T3) in clinically euthyroid patients. (Liothyronine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

• Hypothyroidism and Hyperthyroidism: Monitor thyroid function regularly ( 5.7 ). (Lithium label, Warnings and precautions)

…Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

…Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

An initial increase in serum FT 4 is followed by return of FT 4 to normal levels with sustained therapeutic serum salicylate concentrations, although total T 4 levels may decrease by as much as 30%. (Levothyroxine label, Drug interactions)

An initial increase in serum FT 4 is followed by return of FT 4 to normal levels with sustained therapeutic serum salicylate concentrations, although total T 4 levels may decrease by as much as 30%. (Levothyroxine label, Drug interactions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

…Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Drug or Drug Class Effect Beta-adrenergic antagonists e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Drug or Drug Class Effect Beta-adrenergic antagonists e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. (Levothyroxine label, Drug interactions)

…diverticulosis, and inflammatory bowel disease), hypomotility disorders (e.g., constipation, gastroesophageal reflux disease, ileus, obesity, hypothyroidism, and diabetes) and concomitant medications (e.g., H 2 -histamine blockers, opiates, nonsteroidal anti-inflammatory drugs, laxatives, anticholinergic agents, levothyroxine, and neuromuscular blocking agents). (Nifedipine label, Warnings)

…Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

…1: Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

…1: Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Drug Interactions and Decreased Vitamin Absorption ORLISTAT may interact with concomitant drugs including cyclosporine, levothyroxine, warfarin, amiodarone, antiepileptic drugs, and antiretroviral drugs [see Drug Interactions (7) ]. (Orlistat label, Warnings and precautions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Drug or Drug Class Effect Phenobarbital Rifampin Phenobarbital has been shown to reduce the response to thyroxine. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total and free T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. (Levothyroxine label, Drug interactions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

…Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Hypothyroidism Adults: Clinical trials with quetiapine demonstrated dose-related decreases in thyroid hormone levels. (Quetiapine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Drug or Drug Class Effect Phenobarbital Rifampin Phenobarbital has been shown to reduce the response to thyroxine. (Levothyroxine label, Drug interactions)

Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements. (Levothyroxine label, Drug interactions)

For oral medication where a reduction in the bioavailability of that medication would have a clinically significant effect on its safety or efficacy (e.g., cyclosporine, tacrolimus, levothyroxine), consider separation of the timing of the administration of the two drugs [see Clinical Pharmacology (12.3) ] . (Sevelamer label, Drug interactions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Worsening of Diabetic Control : May worsen glycemic control and result in increased antidiabetic agent or insulin requirements. (Levothyroxine label, Warnings and precautions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

An initial increase in serum FT 4 is followed by return of FT 4 to normal levels with sustained therapeutic serum salicylate concentrations, although total T 4 levels may decrease by as much as 30%. (Levothyroxine label, Drug interactions)

…Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Androgens/Anabolic Steroids Asparaginase Glucocorticoids Slow-Release Nictonic Acid These drugs may decrease serum TBG concentration. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. (Levothyroxine label, Warnings and precautions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine may increase the effects of sympathomimetics or thyroid hormone. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. (Levothyroxine label, Drug interactions)

Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. (Levothyroxine label, Drug interactions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

Effect on Ketone and Thyroid Function Tests Valproate is partially eliminated in the urine as a keto-metabolite which may lead to a false interpretation of the urine ketone test. (Divalproex (valproate) label, Warnings and precautions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

Hypothyroidism has been reported in thyroidectomy patients undergoing levothyroxine replacement. (Imatinib label, Warnings and precautions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

Ketamine Concurrent use of ketamine and levothyroxine may produce marked hypertension and tachycardia. (Levothyroxine label, Drug interactions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

EMROSI may induce hyperpigmentation in many organs, including nails, bone, skin, eyes, thyroid, visceral tissue, oral cavity (teeth, mucosa, alveolar bone), sclerae and heart valves. (Minocycline label, Warnings and precautions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

…performed, the following concomitant drugs were used in at least 10% of patients in either or both Sjogren's efficacy studies: acetylsalicylic acid, artificial tears, calcium, conjugated estrogens, hydroxychloroquine sulfate, ibuprofen, levothyroxine sodium, medroxyprogesterone acetate, methotrexate, multivitamins, naproxen, omeprazole, paracetamol, and prednisone. (Pilocarpine label, Drug interactions)

Changes in thyroid status may occur if barbiturates are added or withdrawn from patients being treated for hypothyroidism. (Levothyroxine label, Drug interactions)

Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-Inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. (Levothyroxine label, Drug interactions)

Effect on Ketone and Thyroid Function Tests Valproate is partially eliminated in the urine as a keto-metabolite which may lead to a false interpretation of the urine ketone test. (Valproic acid label, Warnings and precautions)

…adjustment is needed when SINGULAIR is co-administered with theophylline, prednisone, prednisolone, oral contraceptives, fexofenadine, digoxin, warfarin, gemfibrozil, itraconazole, thyroid hormones, sedative hypnotics, non-steroidal anti-inflammatory agents, benzodiazepines, decongestants, and Cytochrome P450 (CYP) enzyme inducers [see Clinical Pharmacology (12.3)… (Montelukast label, Drug interactions)