Pharmacokinetics of Methimazole in the Normal Cats and Cats with Hyperthyroidism

Treppainer L., Peterson M.E. and Aucoin D.

Vet Intern Med, 1989. 3: p.125 (abst. #50).

Although the antithyroid drug methimazole (MMI; Tapazole) is commonly used in the medical management of cats with hyperthyroidism, pharmacokinetic studies of the drug have not been reported in the cat. In this study, we evaluated the disposition of intravenous and oral MMI in nine clinically normal cats. All cats were given MMI at a total dose of 5 mg either as an IV bolus or as an oral tablet, on consecutive days. Blood for MMI determination (by HPLC) was collected at frequent intervals (5, 15, 30, 60 min, 2, 4, 6, 8, 12, & 24 hours) after dosing. Data was fitted to a one compartment model and the plasm half-life, total body clearance, and volume of distribution of the drug calculated. The area under the concentration vs. time curves (AUC) was determined by the trapezoidal method and the oral bioavailability of MMI calculated by as the ratio of oral/IV AUC.