Adverse Events Of The Thyroid Peroxidase Inhibitor Methimazole In The Treatment Of Hyperthyroidism: A Comprehensive Analysis From The First Quarter Of 2004 To The First Quarter Of 2025

This study analyzed 1,908 patient cases from the US FDA Adverse Event Reporting System database to identify adverse events (AEs) associated with methimazole, a drug used to treat hyperthyroidism, from 2004 to 2025. It confirmed known AEs such as agranulocytosis, pyrexia, and drug-induced liver injury, and identified new potential AEs like premature birth and polyarthritis. The median onset time for AEs was 27 days, indicating early occurrence after starting methimazole. The study emphasizes the need for ongoing pharmacovigilance and further investigation into these newly identified AEs to enhance patient safety and clinical outcomes. Methimazole shows strong hematologic toxicity signals, including pancytopenia and leukopenia, and suggests a potential association with preterm birth, emphasizing careful monitoring, especially in pregnant women. The findings underscore the importance of early detection and intervention, as most adverse events occur within the first month of treatment.