Effect of sulfadiazine and pyrimethamine on selected physiologic and performance parameters in athletically conditioned thoroughbred horses during an incremental exercise stress test

• Published in: Veterinary therapeutics Vol. 3; no. 1; pp. 49 - 63
• Main Authors: Colahan, P.T, Bailey, J.E, Johnson, M, Rice, B.L, Chou, C.C, Cheeks, J.P, Jones, G.L, Yang, M
• Format: Journal Article
• Language: English
• Published: United States 2002
• Subjects: Animals; Antiprotozoal Agents - blood; Antiprotozoal Agents - pharmacokinetics; Antiprotozoal Agents - pharmacology; Antiprotozoal Agents - urine; Blood Cell Count; Blood Glucose; Creatinine - blood; Creatinine - urine; Drug Therapy, Combination; exercise; Exercise Test - drug effects; Exercise Test - veterinary; Female; Folic Acid - blood; Heart Rate - drug effects; horses; Horses - physiology; Male; Oxygen Consumption - drug effects; Physical Conditioning, Animal - physiology; pyrimethamine; Pyrimethamine - blood; Pyrimethamine - pharmacokinetics; Pyrimethamine - pharmacology; Pyrimethamine - urine; sulfadiazine; Sulfadiazine - blood; Sulfadiazine - pharmacokinetics; Sulfadiazine - pharmacology; Sulfadiazine - urine; Thoroughbred; Vitamin B 12 - blood
• ISSN: 1528-3593

Following the regimen used to treat equine protozoal myeloencephalitis, sulfadiazine (20 mg/kg) and pyrimethamine (1mg/kg) were administered orally once daily to 12 physically conditioned Thoroughbred horses for 4 consecutive days. The horses were randomly assigned to two test groups in a crossover design, with each horse serving as its own control. A stepwise exercise stress test was conducted to exhaustion. No effect on athletic performance was observed, and only marginal effects were noted in some hematologic and serochemical measurements, including decreased total white blood cell counts, red blood cell distribution width, total hemoglobin, serum sodium, and serum chloride. Serum folic acid concentration decreased significantly following sulfadiazine/pyrimethamine treatment.