Antithyroid drugs agranulocytosis with

Cooper DS, Goldminz D, Levin AA, Ladenson PW, Daniels GH, Molitch ME, Ridgway EC. Agranulocytosis associated with antithyroid drugs. Effects of patient age and drug dose. Ann Intern Med 1983 98(l) 26-9. 

Outcomes have been reported in a consecutive series of 91 patients hospitalized with non-chemotherapy drug-induced agranulocytosis from 1985-2000 (34). All but two survived. Antithyroid drugs were the cause of agranulocytosis in 20% of cases. Univariate and multivariate analyses failed to reveal a specific effect of antithyroid drugs on the time to neutrophil recovery. In contrast, hemopoietic growth factor treatment was associated with speedier hematological recovery. 

Aplastic anemia due to antithyroid drugs is very rare and has been said to occur as an adverse effect of thionamide therapy with about one-tenth of the frequency of agranulocytosis. 

Antithyroid drugs for long-term therapy (C). Thiourea-derivatives (thioamides) inhibit peroxidase and, hence, hormone synthesis. To restore a euthyroid state, two therapeutic principles can be applied in Graves disease (a) monotherapy with a thioamide, with gradual dose reduction as the disease abates (b) administration of high doses of a thioamide, with concurrent administration of thyroxine to offset diminished hormone synthesis. Adverse effects of thioamides are rare, but the possibility of agranulocytosis has to be kept in mind. 

Perhaps one of the most common side effects is a benign transient leukopenia characterized by a white blood cell (WBC) count of less than 4000/mm. This condition occurs in up to 12% of adults and 25% of children, and sometimes can be confused with mild leukopenia seen in Graves disease. This mild leukopenia is not a harbinger of the more serious adverse effect of agranulocytosis, so therapy can usually be continued. If a minor adverse reaction occurs with one antithyroid drug, the alternate thiourea may be tried, but cross-sensitivity occurs in about 50% of patients. ... 

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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