ExoticRx · exoticrx.com/drugs/valacyclovir
US brand names:Valtrex
Prodrug rapidly converted to acyclovir. Triphosphorylated form inhibits viral DNA polymerase and causes chain termination. Active against herpesviruses.
TOXIC TO CATS — causes acute hepatic necrosis and fatal bone marrow suppression. Dogs tolerate well. Ensure adequate hydration.
Species references:All Cat (Domestic) drugsAll Dog (Domestic) drugs
Each ExoticRx dose rule is graded by the strength of its primary evidence — see the editorial process.
A dog/cat sample is shown here. Cited dosing for all 2 species — reptiles, birds, pocket pets, livestock, and equine — is free on the per-species pages above. Pro adds the weight-based calculator for every species.
| Species | Route | Dose | Frequency | Evidence | Source |
|---|---|---|---|---|---|
| Cat (Domestic) | PO | CONTRAINDICATED IN CATS | N/A | Strong | Nasisse MP, Dorman DC, Jamison KC, Weigler BJ, Hawkins EC, Stevens JB. Effects of valacyclovir in cats infected with feline herpesvivus 1. Am J Vet Res. 1997;58:1141-1144. doi:10.2460/ajvr.1997.58.10.1141 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.1316 (2026-08-01). |
| Dog (Domestic) | PO | 10–20 mg/kg | q8-12h | Moderate | Plumb's Veterinary Drug Handbook, 9th Ed |
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