Methimazole agranulocytosis with

Adverse reactions The most common adverse effect is maculopapular rash. Rarely, hepatitis, vasculitis, urticarial rash, and arthralgia have been observed. Agranulocytosis can occur in 0.3% to 0.6% of patients. Patients who develop agranulocytosis with one thioamide should not be switched to the alternate thioamide because there is a 50% cross-reactivity between the agents. Methimazole is contraindicated during pregnancy because scalp defeas have been observed in infants bom to mothers using methimazole. 

Jin JG, Gao XY, Zhang WL. Treatment of methimazole-induced agranulocytosis with low-dose prednisone and dclosporin following failed treatment with colony-stimulating factors. Clin Endocrinol (Oxf) 2010 73(3) 422-4. 

Adverse effects occur in 3-12% in the form of rash, fever, urticaria, vasculitis, arthralgia, a lupuslike reaction, cholestatic jaundice, hepatitis, lym-phadenopathy and polyserositis but the most dangerous adverse effect is agranulocytosis (it occurs only in 0.3-0.6%). The reaction is readily reversible when the drug is discontinued. Cross-sensitivity between propylthiouracil and methimazole is about 50%, therefore switching drugs in patients with severe reactions is not recommended. 

Tamai H, Sudo T, Kimura A, Mukuta T, Matsubayashi S, Kuma K, Nagataki S, Sasazuki T. Association between the DRB1 08032 histocompatibility antigen and methimazole-induced agranulocytosis in Japanese patients with Graves disease. Ann Intern Med 1996 124(5) 490-4. 

Calabro L, Alonci A, Bellomo G, D Angelo A, Di Giacomo V, Musolino C. Methimazole-induced agranulocytosis and quick recovery with G-CSF case report. Hepatology 2001 5 479-82. 

The successful use of combination treatment of low-dose prednisone and ciclosporin has been reported in a 43-year-old woman with methimazole-induced agranulocytosis, who failed to respond to granulocyte-macrophage CSF (GM-CSF) [15 ]. 

Rayner SG, Hosseini F, Adedipe AA. Sepsis mimicking thyroid storm in a patient with methimazole-induced agranulocytosis. BMJ Case Rep July 16,2013 2013. http //dx.doi.org/10.1136/bcr-2013-200145. 

The frequency of haematological side effects of antithyroid drugs was estimated from questionnaires sent to members of the Philadelphia Endocrine Society 0.6% of 2015 patients developed agranulocytosis during treatment with methimazole compared to 1.8% of 1140 patients treated with propylthiouracil. The frequency of aplastic anaemia was low, only one case being reported in each series (11 ). 

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