Cat · Felis catus · typical adult weight 2.50–7.00 kg
Famciclovir is dosed at 40–90 mg/kg PO q8-12h in cats, per Sebbag L, Thomasy SM, Woodward AP, Knych HK, Maggs DJ. Pharmacokinetic modeling of penciclovir and BRL42359 in the plasma and tears of healthy cats to optimize dosage recommendations for oral administration of famciclovir. Am J Vet Res. 2016;77(8):833-845. doi:10.2460/ajvr.77.8.833 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.526 (2026-08-01).. Famciclovir is used in cats for FHV-1 infections, FHV-1 ophthalmologic (keratitis), FHV-1 dermatitis. Routes documented in cats: PO. A typical adult cat weighs 2.50–7.00 kg. ExoticRx lists 3 cited dose rules for Famciclovir in cats, drawn from published veterinary references. Verify against current literature before clinical use.
US trade names: Famvir
| Route | Dose | Frequency | Duration | Indication | Evidence | Source |
|---|---|---|---|---|---|---|
| PO | 40–90 mg/kg | q8-12h | 7-21 days | FHV-1 infections | Strong | Sebbag L, Thomasy SM, Woodward AP, Knych HK, Maggs DJ. Pharmacokinetic modeling of penciclovir and BRL42359 in the plasma and tears of healthy cats to optimize dosage recommendations for oral administration of famciclovir. Am J Vet Res. 2016;77(8):833-845. doi:10.2460/ajvr.77.8.833 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.526 (2026-08-01). |
| PO | 90 mg/kg | q8h | 14-21 days | FHV-1 ophthalmologic (keratitis) | Strong | Sebbag L, Thomasy SM, Woodward AP, Knych HK, Maggs DJ. Pharmacokinetic modeling of penciclovir and BRL42359 in the plasma and tears of healthy cats to optimize dosage recommendations for oral administration of famciclovir. Am J Vet Res. 2016;77(8):833-845. doi:10.2460/ajvr.77.8.833 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.526 (2026-08-01). |
| PO | 62.5–125 mg per cat | q12h | 14-21 days | FHV-1 dermatitis | Moderate | Papich, Saunders Handbook of Veterinary Drugs, 4th ed. (2016), printed p.310 (corpus papich p.338) — Small Animal Dosage, Cats: "Treatment of feline herpes: 62.5 mg per cat PO q8h for 3 weeks. However, a higher dose of 125 mg per cat q8h may be more effective. Lower doses should be used in kittens (30-50 mg/kg oral q12h)." Same monograph, printed p.309: "higher doses of 125 mg or more every 8-12 hours are now recommended based on clinical observations"; Instructions for Use, p.309: "a higher dose of 125 mg per cat every 8-12 hours oral was more effective." |
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Prodrug of penciclovir. Inhibits viral DNA polymerase in herpesvirus. Used for feline herpesvirus-1 (FHV-1) infections.
First-line antiviral for FHV-1 in cats. Higher doses needed in cats (90mg/kg) due to lower conversion to penciclovir. Well tolerated. May cause GI upset.
Species-specific contraindications and adverse-reaction reports for cats may differ from canine / feline reference data — consult the primary citations listed with each rule.
Famciclovir dose ranges in cats, with cited source references: PO 40–90 mg/kg q8-12h; PO 90 mg/kg q8h; PO 62.5–125 mg per cat q12h. Reference ranges from cited sources — verify against current literature before clinical use.
Documented routes for Famciclovir in cats: PO.
Cited course lengths for Famciclovir in cats include: 7-21 days; 14-21 days. Duration depends on the indication — match it to the specific dose rule in the table above.
Famciclovir is indicated in cats for: FHV-1 infections, FHV-1 ophthalmologic (keratitis), FHV-1 dermatitis.
These are general warnings for Famciclovir across species; consult the cat dosing table above for species-specific guidance. First-line antiviral for FHV-1 in cats. Higher doses needed in cats (90mg/kg) due to lower conversion to penciclovir. Well tolerated. May cause GI upset.
Why a species-specific page? Famciclovir 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.