Trimethoprim in combination with either sulfamethoxazole (SMZ) or sulfadiazine (SDZ) has a wide spectrum of activity against gram negative and positive organisms. There are trimethoprim / sulfadiazine products approved for use in horses in both injectable and oral dosage forms. Many veterinarians also will use the human approved generic trimethoprim / sulfamethoxazole tablets because of economic considerations. In Canada, sulfadoxine is available in combination with trimethoprim for veterinary use. Unfortunately, because of its ease of administration and relatively few side effects, this antibiotic has become very popular for minor wounds and uncomplicated upper respiratory infections. The wounds should receive good care and the respiratory infections are frequently viral and therefore non responsive to anything but time. Overuse continues to lessen the effectiveness of this antibiotic as demonstrated by the increasing resistance among pathogens.

This article is about the use, contraindications, toxic effects, dosages, and association drug rules that apply to this medication.

Unless otherwise instructed by the manufacturer TMP sulfa products should be stored at room temperature in tight containers.