Equine · Equus caballus · typical adult weight 350.00–700.00 kg
Trimethoprim-Sulfamethoxazole is dosed at 24 mg/kg PO q12h for 10 days in horses, per Plumb's Veterinary Drug Handbook, 9th Ed, p.1223 (Sulfa-/Trimethoprim, Dosages, HORSES). Trimethoprim-Sulfamethoxazole is used in horses for Severe bacterial infection, Bacterial infection, Susceptible bacterial infections. Routes documented in horses: PO. A typical adult horse weighs 350.00–700.00 kg. ExoticRx lists 3 cited dose rules for Trimethoprim-Sulfamethoxazole in horses, drawn from published veterinary references. Verify against current literature before clinical use.
US trade names: Bactrim, TMS
| Route | Dose | Frequency | Duration | Indication | Evidence | Source |
|---|---|---|---|---|---|---|
| PO | 24 mg/kg | q12h for 10 days | 5-7 days | Severe bacterial infection | Moderate | Plumb's Veterinary Drug Handbook, 9th Ed, p.1223 (Sulfa-/Trimethoprim, Dosages, HORSES) |
| PO | 24–30 mg/kg | q12h | 7-14 days | Bacterial infection | Strong | EQUISUL-SDT - Sulfadiazine and Trimethoprim Suspension [US Product Label for Horses]. Aurora Pharmaceutical, Inc.; 2021. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=434cfb08-bb19-46fc-a55d-b9ecf0bec601; Winther L, Guardabassi L, Baptiste KE, Friis C. Antimicrobial disposition in pulmonary epithelial lining fluid of horses. Part I. Sulfadiazine and trimethoprim. J Vet Pharmacol Ther. 2011;34(3):277-284. doi:10.1111/j.1365-2885.2010.01229.x — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.1223 (2026-08-01). |
| PO | 24–30 mg/kg | q12h | 7-14 days | Susceptible bacterial infections | Strong | EQUISUL-SDT - Sulfadiazine and Trimethoprim Suspension [US Product Label for Horses]. Aurora Pharmaceutical, Inc.; 2021. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=434cfb08-bb19-46fc-a55d-b9ecf0bec601; Winther L, Guardabassi L, Baptiste KE, Friis C. Antimicrobial disposition in pulmonary epithelial lining fluid of horses. Part I. Sulfadiazine and trimethoprim. J Vet Pharmacol Ther. 2011;34(3):277-284. doi:10.1111/j.1365-2885.2010.01229.x — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.1223 (2026-08-01). |
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These ranges are per kg. Enter your horse's weight to get the precise dose and draw-up volume — unit and concentration math done for you.
Sequential blockade of folate synthesis: sulfamethoxazole inhibits dihydropteroate synthase; trimethoprim inhibits dihydrofolate reductase.
May cause keratoconjunctivitis sicca (KCS) in dogs with prolonged use. Can cause bone marrow suppression. Avoid in animals with hepatic disease. Adequate hydration required.
Species-specific contraindications and adverse-reaction reports for horses may differ from canine / feline reference data — consult the primary citations listed with each rule.
Trimethoprim-Sulfamethoxazole dose ranges in horses, with cited source references: PO 24 mg/kg q12h for 10 days; PO 24–30 mg/kg q12h; PO 24–30 mg/kg q12h. Reference ranges from cited sources — verify against current literature before clinical use.
Documented routes for Trimethoprim-Sulfamethoxazole in horses: PO.
Cited course lengths for Trimethoprim-Sulfamethoxazole in horses include: 5-7 days; 7-14 days. Duration depends on the indication — match it to the specific dose rule in the table above.
Trimethoprim-Sulfamethoxazole is indicated in horses for: Severe bacterial infection, Bacterial infection, Susceptible bacterial infections.
These are general warnings for Trimethoprim-Sulfamethoxazole across species; consult the horse dosing table above for species-specific guidance. May cause keratoconjunctivitis sicca (KCS) in dogs with prolonged use. Can cause bone marrow suppression. Avoid in animals with hepatic disease. Adequate hydration required.
Why a species-specific page? Trimethoprim-Sulfamethoxazole pharmacokinetics differ across species: dose ranges, intervals, and route preferences are not interchangeable. Cross-extrapolation from canine doses is unsafe in horses — the rules above are the citations specific to this species, not generic recommendations.
Sourced from published veterinary references; awaiting credentialed clinical reviewer. See our editorial process. Reference only — not veterinary advice.