Agranulocytosis Associated with Antithyroid Drugs

Publisher Website
Google Scholar
Abstract
The records of all patients with antithyroid drug-related agranulocytosis at 2 hospitals (group 1, 14 patients) and the published case reports of 36 patients with this syndrome (group 2) were reviewed. The clinical characteristics of these patients were compared with those of 50 hyperthyroid patients who had taken antithyroid medication without untoward hematologic reactions (group 3). The mean ages of patients in groups 1 and 2 were significantly greater than that in 3 (50.6 .+-. 16 vs. 35.7 .+-. 13.7 yr, P < 0.001; 46.3 .+-. 18.7 vs. 35.7 .+-. 13.7 yr, P < 0.02). By chi-squared analysis, the relative risk of developing agranulocytosis in patients over age 40 yr was 6.4 times that among younger patients (P < 0.001). The mean doses of methimazole in groups 1 and 2 were significantly higher than that in 3 (43.8 .+-. 9.9 vs. 29.5 .+-. 10.4 mg/day, P < 0.001; 40.7 .+-. 15.7 vs. 29.5 .+-. 10.4 mg/day, P < 0.02), with an 8.6-fold increased risk of agranulocytosis with doses > 40 mg/day (P < 0.01). The mean doses of propylthiouracil did not differ among the 3 groups. Evidently, antithyroid drugs should be administered cautiously to patients over age 40 yr. Because no cases of agranulocytosis were seen with methimazole doses < 30 mg/day low-dose methimazole therapy may be safer than high-dose therapy or treatment with conventional doses of propylthiouracil.