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Carbimazole for Feline Hyperthyroidism

Frenais, R., S. Burgaud, et al. (2008). “Pharmacokinetics of controlled-release carbimazole tablets support once daily dosing in cats.” Journal of Veterinary Pharmacology and Therapeutics 31(3): 213-219.

Carbimazole is a common oral treatment for feline hyperthyroidism, although not in North America. Carbimazole is a prodrug, as it is converted to methimazole after metabolism. Methimazole reduces production of the thyroid hormones, T3 and T4. The pharmacokinetics of methimazole was investigated in healthy cats following oral administration of 15 mg of carbimazole as a newly available controlled-release tablet (Vidalta®, Intervet). Methimazole levels were sustained and without a peak when compared to dosing with conventional carbimazole tablets. Repeated oral dosing for 13 days did not lead to accumulation of methimazole in plasma. Absorption of carbimazole was improved when administered with food. The relative oral bioavailability of methimazole following administration of the controlled-release tablets was similar to that of a conventional release formulation (83 ± 21%). The pharmacokinetics of this controlled-release formulation of carbimazole supports its use as a once daily treatment (both as a starting dose and for maintenance therapy) for cats with hyperthyroidism.
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Related articles:
Bucknell, D. G. (2000). “Feline hyperthyroidism: spectrum of clinical presentions and response to carbimazole therapy.” Aust Vet J 78(7): 462-5.