Thyrozol® (thiamazole; synonym: methimazole): New risk of acute pancreatitis and update on risk of congenital malformations

Merck would like to inform healthcare professionals of the new risk of acute pancreatitis and to update on the risk of congenital malformations associated with carbimazole or thiamazole. Cases of acute pancreatitis have been reported following treatment with carbimazole or thiamazole. If acute pancreatitis occurs, treatment with carbimazole or thiamazole should be discontinued immediately. As re-exposure may result in recurrence of acute pancreatitis, with decreased time to onset, these medicines must not be given to patients with a history of acute pancreatitis with carbimazole or thiamazole. In addition, there have been evidence from retrospective cohort and epidemiological studies showing an increased risk of congenital malformations with carbimazole or thiamazole, particularly when administered in the first trimester of pregnancy and at high doses. When carbimazole or thiamazole is given during pregnancy, close maternal, fetal and neonatal surveillance is recommended. Please refer to the letter for details.