Equisul-SDT Oral Suspension is used in the treatment of lower respiratory tract infections in horses. Each ml of Equisul-SDT Oral Suspension contains 67 mg trimethoprim and 333 mg sulfadiazine in an aqueous suspension. Oral dosage may be recommended at the rate of 2.7 ml per 100 lbs. body weight twice daily for 10 days. Trimethoprim and sulfadiazine.