A retrospective evaluation of adverse reactions to trimethoprim-sulphonamide combinations in dogs and cats.

Adverse reactions to various trimethoprim-sulphonamide (T-S) combinations were studied retrospectively in dogs and cats referred to the Utrecht University Department of Clinical Sciences of Companion Animals during the period 1985-1994. Dermatological and systemic reactions were observed in 19 dogs and 2 cats. Specific histological reaction patterns were seen in 3 dogs with toxic epidermal necrolysis, in 1 dog and 1 cat with erythema multiforme, and in 1 dog with pemphigus foliaceus. Diagnostic criteria used in humans proved to be reliable in dogs and cats as well. Adverse reactions were observed within 7-14 days after administration and were most often due to sulphadiazine (76%) and sulphatroxazole (14%). The incidence of adverse reactions to T-S was 0.25%.