Cat · Felis catus · typical adult weight 2.50–7.00 kg
Trimethoprim-Sulfamethoxazole is dosed at 15–30 mg/kg PO q12h in cats, per Weese JS, Blondeau J, Boothe D, et al. International Society for Companion Animal Infectious Diseases (ISCAID) guidelines for the diagnosis and management of bacterial urinary tract infections in dogs and cats. Vet J. 2019;247:8-25. — Plumb's Veterinary Drug Handbook, 10th Ed, p.1196. Trimethoprim-Sulfamethoxazole is used in cats for Nocardia infections, Bacterial cystitis - complicated UTI (extra-label), Complicated bacterial cystitis (UTI), Bacterial cystitis/UTI (complicated), coccidiosis. Routes documented in cats: PO. A typical adult cat weighs 2.50–7.00 kg. ExoticRx lists 4 cited dose rules for Trimethoprim-Sulfamethoxazole in cats, 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 | 15–30 mg/kg | q12h | 6-12 weeks | Nocardia infections | Moderate | Weese JS, Blondeau J, Boothe D, et al. International Society for Companion Animal Infectious Diseases (ISCAID) guidelines for the diagnosis and management of bacterial urinary tract infections in dogs and cats. Vet J. 2019;247:8-25. — Plumb's Veterinary Drug Handbook, 10th Ed, p.1196 |
| PO | 15–30 mg/kg | q12h | Course length not printed for the complicated arm | Bacterial cystitis - complicated UTI (extra-label) | Moderate | Plumb's Veterinary Drug Handbook, 10th ed (2023), p.1223 (Sulfa-/Trimethoprim, Dosages, CATS); corroborated by BSAVA Small Animal Formulary 10th Ed Part A p.419 'Dogs, Cats: 15-30 mg/kg p.o. q12h' — Plumb's Veterinary Drug Handbook, 10th ed, Sulfa-/Trimethoprim monograph, printed p.1196, CATS: "Bacterial cystitis (extra-label):. b) Complicated UTI: 15 - 30 mg/kg PO every 12 hours."; same monograph, printed p.1195: "Unless otherwise noted, doses are for combined sulfa-/trimethoprim."Compilation only — we have not located an independent source that prints this figure. |
| PO | 15–30 mg/kg | q12h | 21 days | Complicated bacterial cystitis (UTI) | Weak | Weese JS, Blondeau J, Boothe D, et al. International Society for Companion Animal Infectious Diseases (ISCAID) guidelines for the diagnosis and management of bacterial urinary tract infections in dogs and cats. Vet J. 2019;247:8-25. doi:10.1016/j.tvjl.2019.02.008 — Plumb's Veterinary Drug Handbook, 10th Ed, p.1196 |
| PO | 15–30 mg/kg | q12h | 14-21 days | Bacterial cystitis/UTI (complicated), coccidiosis | Strong | Weese JS, Blondeau J, Boothe D, et al. International Society for Companion Animal Infectious Diseases (ISCAID) guidelines for the diagnosis and management of bacterial urinary tract infections in dogs and cats. Vet J. 2019;247:8-25. doi:10.1016/j.tvjl.2019.02.008 — Plumb's Veterinary Drug Handbook, 10th Ed, p.1196 |
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These ranges are per kg. Enter your cat'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 cats may differ from canine / feline reference data — consult the primary citations listed with each rule.
Trimethoprim-Sulfamethoxazole dose ranges in cats, with cited source references: PO 15–30 mg/kg q12h; PO 15–30 mg/kg q12h; PO 15–30 mg/kg q12h; PO 15–30 mg/kg q12h. Reference ranges from cited sources — verify against current literature before clinical use.
Documented routes for Trimethoprim-Sulfamethoxazole in cats: PO.
Cited course lengths for Trimethoprim-Sulfamethoxazole in cats include: 6-12 weeks; Course length not printed for the complicated arm; 21 days; 14-21 days. Duration depends on the indication — match it to the specific dose rule in the table above.
Trimethoprim-Sulfamethoxazole is indicated in cats for: Nocardia infections, Bacterial cystitis - complicated UTI (extra-label), Complicated bacterial cystitis (UTI), Bacterial cystitis/UTI (complicated), coccidiosis.
These are general warnings for Trimethoprim-Sulfamethoxazole across species; consult the cat 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 cats — 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.