Vincristine in the treatment of thrombocytopenia in five dogs.

Five dogs with idiopathic thrombocytopenic purpura were successfully treated with vincristine alone or in combination with a glucocorticoid. Glucocorticoid therapy alone appeared ineffective in increasing the platelet count. Four dogs were effectively treated after a single dose of vincristine, but the remaining dog required an additional dose. Vincristine, although effective, is not recommended as the primary therapy of idiopathic thrombocytopenia in the dog. High cost and potential side effects should make its use restricted to cases in which glucocorticoid therapy is either ineffective or contraindicated.