Acyclovir inhibits viral replication (viral DNA polymerase); depends on viral thymidine kinase for phosphorylation.
Uses of Acyclovir in Dogs, Cats, Horses and Birds
Feline Herpesvirus Type 1 (FHV-1): Primarily used as an ophthalmic ointment to treat infections of the eyes caused by FHV-1.
Canine Herpesvirus (CHV): Occasionally used as adjunctive treatment for neonatal herpes infections.
Equine Herpesvirus: Investigated as a treatment for equine herpesvirus infections, though oral bioavailability is limited.
Birds (Psittacine species): Utilized for treating psittacid alphaherpesvirus-1 (formerly Pacheco’s disease) when administered early.
Dose of Acyclovir in Dogs, Cats, Horses and Birds
Species
Condition
Dosage
Dogs
Canine Herpesvirus
10 mg/kg orally every 6 hours for 5 days (extra-label use).
Cats
Feline Herpesvirus (ophthalmic)
Apply ointment 5 times daily for up to 3 weeks.
Horses
Neonatal Equine Herpesvirus
10 mg/kg IV every 12 hours for neonatal foals.
Birds
Psittacid Alphaherpesvirus-1
80 mg/kg orally every 8 hours for 7 days.
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Side Effects of Acyclovir in Dogs, Cats, Horses and Birds
Cats: Ocular irritation from topical use; systemic use is not recommended due to risks of myelosuppression, renal tubular necrosis, and hepatic necrosis.
Dogs: GI signs such as vomiting and diarrhea, and renal toxicity at high doses.
Birds: Tissue necrosis at injection sites; nephrotoxicity possible with rapid IV administration.
Horses: Tremors, sweating, and colic when given IV over a short period.
Contraindications of Acyclovir in Dogs, Cats, Horses and Birds
Cats: Systemic use is contraindicated due to severe toxicity risks.
Dogs and Horses: Use cautiously in animals with renal impairment or dehydration.
Birds: Avoid rapid IV administration due to risk of necrosis.
Some Notes:
Alternative Treatments: Famciclovir and ganciclovir are preferred for feline herpes infections due to better safety profiles.
Drug Interactions:
Nephrotoxic Drugs (e.g., aminoglycosides, amphotericin B) can increase the risk of nephrotoxicity.
Probenecid: Increases acyclovir exposure by inhibiting renal clearance.
Theophylline: May raise theophylline concentrations; monitor when using concurrently.
Monitoring: Regular renal function tests (BUN, serum creatinine) are recommended with prolonged use or IV administration.
Overdose Management: GI decontamination is recommended for overdoses ≥150 mg/kg. Acyclovir is removed by hemodialysis, but not by peritoneal dialysis.
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