Bioavailability of two tablet preparations of carbimazole in man

1. The bioavailability of two 5 mg tablet formulations of carbimazole (Neomercazole [A] and Carbazole [B]) have been compared in six euthyroid subjects. There was considerable inter-patient variation in absolute bioavailability although, for each subject, peak plasma concentrations of methimazole were similar with both formulations. 2. Mean peak plasma concentrations were seen on average 62 min after administration of tablet A as compared to 40 min after tablet B. This is consistent with the finding that the disintegration and dissolution times were shorter for formulation B than for formulation A. The mean area under the plasma concentration curve and the 6 h plasma concentration of methimazole tended to be greater after tablet A. These differences could be of significance in the treatment of thyrotoxicosis.