Serum concentrations of methimazole in cats after a single oral dose of controlled-release carbimazole or sugar-coated methimazole (thiamazole).
Methimazole (thiamazole) is an antithyroid drug commonly used to treat feline hyperthyroidism. It is routinely given twice daily. Carbimazole is a methimazole derivative that is rapidly metabolized to methimazole in vivo. A controlled-release tablet for once-daily carbimazole therapy has recently been developed in an attempt to improve compliance during medical management of feline hyperthyroidism. The results of a crossover study in six cats suggest that the pharmacokinetics of methimazole with a single dose of this controlled-release tablet may be similar to those with a single dose of a sugar-coated methimazole tablet when the two drugs are given at an equimolar dose. The mean half-lives were nearly identical (3.12 hours, sugar-coated methimazole tablets; 3.28 hours, controlled-release carbimazole tablets). The serum concentrations of methimazole at 24 hours were 21.7 ± 28.9 ng/mL in the cats treated with 5-mg sugar-coated methimazole tablets and 28.7 ± 37 ng/mL in the cats treated with 10-mg carbimazole tablets (which provide approximately 25% more methimazole after conversion to the active metabolite).
Dechra Ltd., Shrewsbury, Shropshire, UK. susan.longhofer@dechra.com
Susan L
SL
Longhofer
Tomás
T
Martín-Jiménez
Jyoti
J
Soni-Gupta
D000818:Animals; D013956:Antithyroid Agents / Q000097:blood / Q000493:pharmacokinetics*; D002231:Carbimazole / Q000097:blood / Q000493:pharmacokinetics*; D002415:Cats; D018592:Cross-Over Studies; D003692:Delayed-Action Preparations; D005260:Female; D008297:Male; D008713:Methimazole / Q000097:blood / Q000493:pharmacokinetics*
D013956:Antithyroid Agents; D003692:Delayed-Action Preparations; D008713:Methimazole; D002231:Carbimazole