Methimazole-induced Cholestatic Jaundice

Abstract

Methimazole is a widely used and generally well-tolerated antithyroid agent. A 43-year-old woman had severe jaundice and itching 1 month after receiving methimazole (10 mg tid) and propranolol (20 mg tid) for treatment of hyperthyroidism. The patient continued treatment for another 4 days after the appearance of jaundice until she finished both medications. When seen at the emergency department 2 weeks later, she still had severe icterus, pruritus, and hyperbilirubinemia, formed mainly of the conjugated fraction. Methimazole-induced cholestasis was diagnosed, and propranolol therapy was resumed. Over the following 9 days, the symptoms improved and plasma bilirubin levels were normal after 12 weeks without methimazole. In rare cases within the first few weeks of therapy, this drug can cause severe and reversible cholestatic jaundice. Physicians and patients should be aware of this adverse effect so that, upon occurrence, they can discontinue methimazole therapy and avoid unnecessary invasive procedures.