Methimazole-induced hepatotoxicity

Abstract

Objective: To present the case of a patient with Graves' hyperthyroidism in whom treatment with methimazole led to severe cholestasis.

Methods: A detailed case report and an overview of previously published cases of methimazole- and carbimazole-induced hepatotoxicity, found in a MEDLINE search with use of methimazole, carbimazole, thionamides and antithyroid agents as subject headings, are provided.

Results: In a 36-year-old woman with severe hyperthyroidism, treatment with methimazole (20 mg twice daily) was initiated. Nineteen days later, pruritus, scleral icterus, dark urine, and abdominal discomfort prompted discontinuation of the therapy. Laboratory investigations and abdominal ultrasonography showed findings consistent with a cholestatic reaction to methimazole. Recovery was slow but complete. Of the 30 previously published cases of hepatotoxicity related to treatment with methimazole or carbimazole in which the nature of the hepatic injury was described, 19 were also cholestatic.

Conclusion: Physicians should be aware that thionamide drugs can be associated with hepatotoxicity. Analysis of the known cases suggests that older age of the patient and higher dose of the drug are risk factors for cholestatic injury.