The European Agency for the Evaluation of Medicinal Products Veterinary Medicines Evaluation Unit

1. Trimethoprim is a diaminopyrimidine antimicrobial agent which is effective against a wide range of Gram-positive and Gram-negative organisms. In veterinary medicine, trimethoprim is commonly used in combination with a sulphonamide in a concentration ratio of 1:5. It is administered orally, as a bolus, paste or in the drinking water or feed to calves, pigs, horses, poultry and fish (5 mg/kg bw trimethoprim+25 mg/kg bw sulphonamide). Injectable formulations are also available for the treatment of pigs, cattle, goats and horses 15-30 mg/kg bw of combined active ingredients, 1-2 times per day). Treatment is normally repeated for up to 5 days (up to 7 days for fish). There is also an intramammary preparation for cattle containing 40 mg trimethoprim+200 mg sulphadiazine. In some countries trimethoprim was also administered to other species such as sheep and llamas but details of the dosing regimes were not available. Trimethoprim is currently entered into Annex III of Council Regulation (EEC) No 2377/90 as follows: