Effects of Methimazole on Hemostatic Parameters in Cats with Hyperthyroidism

Reine N.J., Peterson M.E. and Hohenhaus A.E.

J Vet Intern Med, 1999. 13: p.245 (abstract).

Thrombocytopenia is a rare but well recognized side effect of methimazole (Tapazole) treatment in cats. Methimazole has also been implicated in producing a bleeding tendency in cats with a normal platelet count. Because of that, some have recommended not using methimazole to make cats euthyroid prior to surgery, in the belief that this bleeding tendency would increase the bleeding associated with surgery and therefore surgical risk. In this study, we investigated for hemostatic abnormalities caused by the administration of methimazole to cats with hyperthyroidism. Thirteen hyperthyroid cats were evaluated before and again after 3-4 weeks after treatment with methimazole (5-15 mg/day).