Cat · Felis catus · typical adult weight 2.50–7.00 kg
Trimethoprim 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. doi:10.1016/j.tvjl.2019.02.008 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.1223 (2026-08-01). — LOCATOR CONVENTION 2026-08-07: the bare 'p.1223' in this citation is the PDF index of the held scan, not the printed page. The PRINTED page is p.1196; verified by finding the drug named there. If you are holding the book, turn to p.1196. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207. Trimethoprim is used in cats for Complicated UTI (bacterial cystitis) - dose is COMBINED sulfonamide plus trimethoprim. Routes documented in cats: PO. A typical adult cat weighs 2.50–7.00 kg. ExoticRx lists 1 cited dose rule for Trimethoprim in cats, drawn from published veterinary references. Verify against current literature before clinical use.
US trade names: Tribrissen
| Route | Dose | Frequency | Duration | Indication | Evidence | Source |
|---|---|---|---|---|---|---|
| PO | 15–30 mg/kg | q12h | 7-14 days | Complicated UTI (bacterial cystitis) - dose is COMBINED sulfonamide plus trimethoprim | 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 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.1223 (2026-08-01). — LOCATOR CONVENTION 2026-08-07: the bare 'p.1223' in this citation is the PDF index of the held scan, not the printed page. The PRINTED page is p.1196; verified by finding the drug named there. If you are holding the book, turn to p.1196. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207 |
Every held source for this drug and species, as printed. Where they differ, both are shown — the choice is yours, not ours.
| Dose (mg/kg) | Route | Source | As printed |
|---|---|---|---|
| 15–30 | PO | BSAVA Small Animal Formulary, 10th ed — Part A (Canine and Feline)p.435 | 15-30 mg/kg p.o. q12h. 30 mg/kg s.c. q24h. |
| 30 | SC | BSAVA Small Animal Formulary, 10th ed — Part A (Canine and Feline)p.435 | 15-30 mg/kg p.o. q12h. 30 mg/kg s.c. q24h. |
| 15 | PO | Papich Saunders Handbook of Veterinary Drugs, 4th edp.848 | • 15 mg/kg q12h PO or 30 mg/kg q12-24h PO. |
| 30 | PO | Papich Saunders Handbook of Veterinary Drugs, 4th edp.848 | • 15 mg/kg q12h PO or 30 mg/kg q12-24h PO. |
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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.
Inhibits dihydrofolate reductase (DHFR) in folate synthesis pathway. Synergistic bactericidal activity when combined with sulfonamides.
Almost always used in combination with a sulfonamide. Folate supplementation recommended in cats and during pregnancy. KCS risk in dogs.
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 dose range in cats, with cited source references: PO 15–30 mg/kg q12h. Reference ranges from cited sources — verify against current literature before clinical use.
Documented routes for Trimethoprim in cats: PO.
Cited course lengths for Trimethoprim in cats include: 7-14 days. Duration depends on the indication — match it to the specific dose rule in the table above.
Trimethoprim is indicated in cats for: Complicated UTI (bacterial cystitis) - dose is COMBINED sulfonamide plus trimethoprim.
These are general warnings for Trimethoprim across species; consult the cat dosing table above for species-specific guidance. Almost always used in combination with a sulfonamide. Folate supplementation recommended in cats and during pregnancy. KCS risk in dogs.
Why a species-specific page? Trimethoprim 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.
| 30 |
| IV |
| Papich Saunders Handbook of Veterinary Drugs, 4th edp.850 |
| • 30 mg/kg q12h IV (see “Instructions for Use” section for preparation of IV |
Figures are transcribed from the cited page or table of each held edition and are shown for reference only. They are not dose recommendations, they do not feed the calculator, and none has been reviewed by a veterinarian.