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Drugs and Foods That Interact with Thyroid Medications

Content provided by the Faculty of the Harvard Medical School
Excerpted from a Harvard Special Health Report

The following medicines and therapies can influence the effectiveness of thyroid medicines in one or more of the following ways: by interfering with the absorption of thyroid hormone, by binding thyroid hormone to binding proteins, and by interfering with thyroid hormone metabolism.

Cancer therapies

  • asparaginase
  • bexarotene*
  • fluorouracil
  • interferon*
  • interleukin*
  • ipilimumab*
  • sunitinib*
  • tamoxifen
  • thalidomide and lenalidomide

Cardiovascular therapies

  • amiodarone*
  • furosemide
  • heparin
  • oral anticoagulants

Cholesterol therapies

  • bile acid sequestrants, including cholestyramine,* clofibrate, and colestipol*
  • slow-release niacin

Gastrointestinal therapies

  • aluminum hydroxide antacids
  • cation-exchange resins
  • charcoal
  • proton-pump inhibitors
  • sucralfate

Hormonal therapies

  • androgens/anabolic steroids
  • dopaminergic drugs including bromocriptine and cabergoline
  • estrogens
  • glucocorticoids such as prednisone
  • growth hormone
  • metoclopramide
  • raloxifene

Neurologic/psychiatric therapies

  • anticonvulsants including phenytoin,* phenobarbital,* and carbamazepine*
  • lithium*
  • sertraline*
  • other antidepressants and antipsychotic agents, including clomipramine and quetiapine

Nutritional supplements

  • calcium carbonate
  • ferrous sulfate (iron)
  • iodine* (including kelp supplements)
  • multivitamins (presumably because of iron and calcium content)


  • espresso coffee
  • grapefruit
  • soy

Other medicines

  • antituberculous drugs (rifampicin, ethionamide)
  • bisphosphonates taken orally, such as alendronate
  • methadone
  • nonsteroidal anti-inflammatory drugs such as meclofenamic acid, mefenamic acid, phenylbutazone
  • orlistat
  • orphenadrine
  • propranolol
  • radiographic agents (such as contrast agents containing iodine)*
  • salicylates (high doses of aspirin and salsalate)
  • sulfonamides (acetazolamide, sulfisoxazole)
  • sulfonylureas

* These drugs can have a major impact on thyroid treatment.

Last Annual Review Date: May 1, 2012 Copyright: 2012 Harvard Health Publications

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