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Methimazole Disease Interactions

There are 3 disease interactions with methimazole.

Major

Thioamide derivatives (applies to methimazole) blood dyscrasias

Major Potential Hazard, Moderate plausibility. Applicable conditions: Neutropenia, Thrombocytopenia

The use of thioamide antithyroid agents may infrequently be associated with the development of blood dyscrasias, primarily agranulocytosis but also leukopenia, thrombocytopenia, and aplastic anemia. Most cases of agranulocytosis occur within the first two months of therapy, with incidence declining gradually thereafter. Patients older than 40 years of age and those receiving more than 40 mg/day of methimazole appear to be at substantially increased risk (a dosage association has not been reported for propylthiouracil). Therapy with thioamide derivatives should be administered cautiously in patients with or predisposed to blood dyscrasias and/or bone marrow depression. Clinical monitoring of hematopoietic function is recommended, with particular focus on leukocyte and differential counts. Because leukopenia (i.e. leukocyte count < 4000/mm3) may also occur in 10% of patients with untreated hyperthyroidism and is often associated with relative granulocytopenia, baseline count should be determined prior to initiating antithyroid medication. Patients should be instructed to immediately report during therapy any signs or symptoms suggestive of myelosuppression such as fever, sore throat, local infection, easy bruising, or bleeding. Cessation of antithyroid drug and institution of appropriate supportive measures are necessary if agranulocytosis or aplastic anemia develops.

References

  1. Cooper DS "Antithyroid drugs." N Engl J Med 311 (1984): 1353-62
  2. Biswas N, Ahn YH, Goldman JM, Schwartz JM "Aplastic anemia associated with antithyroid drugs." Am J Med Sci 301 (1991): 190-4
  3. Valenta LJ, Elias AN, Weber DJ "Hyperthyroidism and propylthiouracil-induced agranulocytosis during chronic lithium carbonate therapy." Am J Psychiatry 138 (1981): 1605-7
  4. Shambaugh GE, 3d Khoury N, Zonschein J, Sizemore GW "Hypocalcemia accompanying agranulocytosis during propylthiouracil therapy." Ann Intern Med 91 (1979): 576-7
  5. Tajiri J, Noguchi S, Murakami T, Murakami N "Antithyroid drug-induced agranulocytosis. The usefulness of routine white blood cell count monitoring." Arch Intern Med 150 (1990): 621-4
  6. "Product Information. Propylthiouracil (propylthiouracil)." Lederle Laboratories (2001):
  7. Hoffman DM, Burgess J, Hill P "Agranulocytosis and hepatic dysfunction following propylthiouracil treatment." Aust N Z J Med 24 (1994): 409-10
  8. American Medical Association, Division of Drugs and Toxicology "Drug evaluations annual 1994." Chicago, IL: American Medical Association; (1994):
  9. Bishara J, Cux S, Pitlik S "Methimazole-induced aplastic anemia." Ann Pharmacother 30 (1996): 684
  10. "Product Information. Tapazole (methimazole)." King Pharmaceuticals Inc (2001):
View all 10 references
Major

Thioamide derivatives (applies to methimazole) hepatotoxicity

Major Potential Hazard, Low plausibility. Applicable conditions: Liver Disease, Alcoholism

The use of thioamide antithyroid agents has been associated with hepatotoxic effects, including transient elevations of serum transaminases and, rarely, cholestatic jaundice, fulminant hepatitis, hepatic necrosis, encephalopathy and death. Therapy with thioamide derivatives should be administered cautiously in patients with preexisting liver disease, a history of alcohol abuse, or hepatitis. Treatment should be discontinued if deterioration in liver function or other signs of hepatic injury occur. The jaundice associated with methimazole-induced hepatitis may persist for several weeks after withdrawal of the medication.

References

  1. Limaye A, Ruffolo PR "Propylthiouracil-induced fatal hepatic necrosis." Am J Gastroenterol 82 (1987): 152-4
  2. Liaw YF, Huang MJ, Fan KD, Li KL, Wu SS, Chen TJ "Hepatic injury during propylthiouracil therapy in patients with hyperthyroidism. A cohort study." Ann Intern Med 118 (1993): 424-8
  3. Safani MM, Tatro DS, Rudd P "Fatal propylthiouracil-induced hepatitis ." Arch Intern Med 142 (1982): 838-9
  4. Hanson JS "Propylthiouracil and hepatitis. Two cases and a review of the literature." Arch Intern Med 144 (1984): 994-6
  5. Seidman DS, Livni E, Ilie B, Blum I "Propylthiouracil-induced cholestatic jaundice." J Toxicol Clin Toxicol 24 (1986): 353-60
  6. "Product Information. Propylthiouracil (propylthiouracil)." Lederle Laboratories (2001):
  7. Hoffman DM, Burgess J, Hill P "Agranulocytosis and hepatic dysfunction following propylthiouracil treatment." Aust N Z J Med 24 (1994): 409-10
  8. Westphal SA "Hepatotoxicity from propylthiouracil." South Med J 87 (1994): 943-7
  9. American Medical Association, Division of Drugs and Toxicology "Drug evaluations annual 1994." Chicago, IL: American Medical Association; (1994):
  10. Ozenirler S, Tuncer C, Boztepe U, Akyol G, Alkim H, Cakir N, Kandilci U "Propylthiouracil-induced hepatic damage." Ann Pharmacother 30 (1996): 960-3
  11. Deidiker R, Demello DE "Propylthiouracil-induced fulminant hepatitis: case report and review of the literature." Pediatr Pathol Lab Med 16 (1996): 845-52
  12. Hardee JT, Barnett AL, Thannoun A, Eghtesad B, Wheeler D, Jamal MM "Propylthiouracil-induced hepatotoxicity." West J Med 165 (1996): 144-7
  13. "Product Information. Tapazole (methimazole)." King Pharmaceuticals Inc (2001):
View all 13 references
Major

Thioamide derivatives (applies to methimazole) hypoprothombinemia

Major Potential Hazard, Low plausibility. Applicable conditions: Bleeding, Coagulation Defect, Thrombocytopathy, Vitamin K Deficiency

Thioamide antithyroid agents may interfere with the action of vitamin K and have been reported in isolated cases to induce hypoprothombinemia and bleeding. Myelosuppression rarely resulting in thrombocytopenia has also been reported. Therapy with thioamide derivatives should be administered cautiously in patients with significant active bleeding or a hemorrhagic diathesis, including hemostatic and/or coagulation defects associated with hemophilia, vitamin K deficiency, hypoprothombinemia, thrombocytopenia, thrombocytopathy, or severe hepatic impairment. Clinical monitoring of prothrombin time or INR is recommended.

References

  1. Sammon TJ, Peden VH, Witzleben C, King JP "Disseminated intravascular coagulation complicating propylthiouracil therapy. A case description of a 16-year-old girl." Clin Pediatr (Phila) 10 (1971): 739-42
  2. "Product Information. Propylthiouracil (propylthiouracil)." Lederle Laboratories (2001):
  3. "Product Information. Tapazole (methimazole)." King Pharmaceuticals Inc (2001):

Methimazole drug interactions

There are 55 drug interactions with methimazole.


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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.