Cat · Felis catus · typical adult weight 2.50–7.00 kg
Pyrimethamine is dosed at 0.25–0.5 mg/kg PO q12h in cats, per Foster SF, Martin P. Lower respiratory tract infections in cats: Reaching beyond empirical therapy. J Feline Med Surg. 2011;13:313-332. doi:10.1016/j.jfms.2011.06.001 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.1127 (2026-08-01). — Plumb's 10th ed (held) printed p.1100, Pyrimethamine monograph spanning p.1099-1100; page located 2026-08-05 from the book's own running heads, and carries this exact dose under the matching species heading. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207. Pyrimethamine is used in cats for Toxoplasmosis. Routes documented in cats: PO. A typical adult cat weighs 2.50–7.00 kg. ExoticRx lists 1 cited dose rule for Pyrimethamine in cats, drawn from published veterinary references. Verify against current literature before clinical use.
US trade names: Daraprim
| Route | Dose | Frequency | Duration | Indication | Evidence | Source |
|---|---|---|---|---|---|---|
| PO | 0.25–0.5 mg/kg | q12h | 14-28 days with trimethoprim-sulfa; taper to q24h after clinical improvement | Toxoplasmosis | Moderate | Foster SF, Martin P. Lower respiratory tract infections in cats: Reaching beyond empirical therapy. J Feline Med Surg. 2011;13:313-332. doi:10.1016/j.jfms.2011.06.001 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.1127 (2026-08-01). — Plumb's 10th ed (held) printed p.1100, Pyrimethamine monograph spanning p.1099-1100; page located 2026-08-05 from the book's own running heads, and carries this exact dose under the matching species heading. — 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.
The sources disagree for this combination. The ranges below do not overlap on a comparable route. This is not an error in one of them — published veterinary references differ, and reconciling them for a particular patient is a clinical judgement.
| Dose (mg/kg) | Route | Source | As printed |
|---|---|---|---|
| 1 | PO | BSAVA Small Animal Formulary, 10th ed — Part A (Canine and Feline)p.370 | Toxoplasmosis/neosporosis: 1 mg/kg p.o. q24h or divided q12h for 4 weeks, alongside sulphonamides. |
| 0.5–1 | PO | Papich Saunders Handbook of Veterinary Drugs, 4th edp.725 | • 0.5-1 mg/kg q24h PO for 14-28 days. |
| 1 | PO | Papich Saunders Handbook of Veterinary Drugs, 4th edp.726 | • 1 mg/kg pyrimethamine and 20 mg/kg sulfadiazine once daily PO. (Equivalent |
| 20 |
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Inhibits dihydrofolate reductase in protozoa, blocking folic acid synthesis required for DNA replication. Synergistic with sulfonamides.
Bone marrow suppression possible — monitor CBC. Supplement with folinic acid (leucovorin). Teratogenic. Do not use in pregnant animals.
Species-specific contraindications and adverse-reaction reports for cats may differ from canine / feline reference data — consult the primary citations listed with each rule.
Pyrimethamine dose range in cats, with cited source references: PO 0.25–0.5 mg/kg q12h. Reference ranges from cited sources — verify against current literature before clinical use.
Documented routes for Pyrimethamine in cats: PO.
Cited course lengths for Pyrimethamine in cats include: 14-28 days with trimethoprim-sulfa; taper to q24h after clinical improvement. Duration depends on the indication — match it to the specific dose rule in the table above.
Pyrimethamine is indicated in cats for: Toxoplasmosis.
These are general warnings for Pyrimethamine across species; consult the cat dosing table above for species-specific guidance. Bone marrow suppression possible — monitor CBC. Supplement with folinic acid (leucovorin). Teratogenic. Do not use in pregnant animals.
Why a species-specific page? Pyrimethamine 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.
| PO |
| Papich Saunders Handbook of Veterinary Drugs, 4th edp.726 |
| • 1 mg/kg pyrimethamine and 20 mg/kg sulfadiazine once daily PO. (Equivalent |
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.