What is the most likely adverse drug reaction associated with carbimazole treatment?

• A. Hypertension
• B. Neutropenia
• C. Rash
• D. Hyperglycemia

Answer: (B)

Carbimazole, a thionamide antithyroid drug, can cause bone marrow suppression that leads to neutropenia, and in its more severe form agranulocytosis. This reduction in neutrophils markedly raises infection risk and can present with fever, sore throat, or other signs of infection, sometimes without obvious cause. Although the overall frequency is low, this adverse effect is the most important and characteristic concern with carbimazole, so it’s emphasized in clinical practice and exams. Rash can occur but is less specific, while hypertension and hyperglycemia are not typical effects of this medication. If neutropenia is suspected, the drug is stopped and a blood count is obtained promptly, with urgent evaluation and appropriate infection management as needed.