Q: 27 years old female is admitted to ICU with severe symptomatic Grave's disease. Pharmacy informed you that methimazole is unavailable but carbimazole can be made available. If carbimazole is used to treat Grave's disease, its conversion in the body is? (select one)
A) higher than methimazole
B) lower than methimazole
Although not approved in the USA, in few countries Carbimazole is more readily available than methimazole. It is a prodrug and gets metabolized to methimazole in the body and provides almost 25-40% higher concentration than intended.
The dose in severe symptomatic Grave's disease is 20 to 40 mg/day
References:Page SR, Sheard CE, Herbert M, Hopton M, Jeffcoate WJ. A comparison of 20 or 40 mg per day of carbimazole in the initial treatment of hyperthyroidism. Clin Endocrinol (Oxf). 1996 Nov;45(5):511-6. doi: 10.1046/j.1365-2265.1996.00800.x. Erratum in: Clin Endocrinol (Oxf) 1997 Feb;46(2):240. PMID: 8977745.