The pharmacokinetics of methimazole after oral administration of carbimazole and methimazole, in hyperthyroid patients.

1 Methimazole plasma concentrations were measured in two groups of hyperthyroid subjects after the oral administration of either carbimazole or methimazole. 2 With the HPLC method it was also possible to measure the concentration of a methimazole metabolite, 3-methyl-2-thiohydantoin in one patient. 3 Large interindividual differences were observed, especially within the carbimazole group. 4 Incomplete absorption of carbimazole could explain particular high apparent volumes of distribution and apparent clearances.