Acyclovir Oral Suspension
Acyclovir is an antiviral used mainly to treat herpesvirus infections, especially in birds (such as psittacines) with avian herpesvirus disease.
The uses and pharmacology described below reflect the FDA-approved labeling for this active ingredient; your veterinarian determines whether and how they apply to your animal's treatment plan.
Veterinarians most commonly consider acyclovir in the context of equine herpesvirus-1 (EHV-1), particularly during outbreaks where neurological or respiratory signs are a clinical priority. In feline medicine, it may be a point of discussion for managing clinical signs associated with feline herpesvirus-1 (FHV-1) when ocular health or upper respiratory stability is a concern. By interfering with the replication cycle of the virus, your veterinarian can manage the physiological progression of the viral load within the patient.
At a pharmacological level, acyclovir acts as a selective inhibitor of viral DNA polymerase. The medication is a prodrug that must undergo phosphorylation by a virus-specific enzyme, thymidine kinase, to its active triphosphate form. Once activated, it acts as a substitute for deoxyguanosine triphosphate, competing for the viral DNA polymerase and causing premature termination of the growing viral DNA chain. Because the initial activation step requires a viral enzyme, acyclovir has a high affinity for infected cells while remaining relatively inactive in healthy host cells. Your veterinarian will determine whether acyclovir is appropriate for your pet based on species-specific absorption rates and the nature of the prescriptions required for the clinical situation.
Prescription only. Use only under the direction of a licensed veterinarian. This information is not a substitute for veterinary diagnosis, prescribing or monitoring. Compounded drugs are not approved by the FDA for safety or effectiveness.
Commonly observed effects of acyclovir administration can vary significantly by species; for instance, cats may be more susceptible to localized irritation or digestive shifts. In some patients, veterinarians monitor for signs of bone marrow suppression or changes in kidney function, especially during prolonged or high-dose protocols. Owners should watch for behavioral shifts such as lethargy, a decrease in appetite or vomiting and contact their veterinarian promptly with any concerns.
This medication is typically used with extra caution or avoided in patients with known pre-existing renal impairment, as the kidneys are the primary route of excretion for the active metabolite. Because acyclovir has limited oral bioavailability in certain species—particularly dogs—your veterinarian may discuss alternative antiviral options or customized medications to ensure the management approach remains appropriate. Your veterinarian is the right person to provide guidance on the necessary duration of therapy and the appropriate monitoring schedule to ensure the approach remains suitable for your pet's individual health status.
Yes. Acyclovir is a prescription antiviral medication and can only be dispensed by a licensed pharmacy upon receipt of a valid authorization from a licensed veterinarian. Mixlab verifies all authorizations before any medication is prepared or shipped.
Yes. While acyclovir is available in commercial tablet and injectable formats, Mixlab can compound this medication into specialized strengths or alternative dosage forms—such as flavored oral liquids—if your veterinarian determines a customized preparation better suits your pet's needs. The decision between a commercial and compounded product rests with the prescribing veterinarian.
Veterinarians discuss acyclovir because it specifically targets the DNA replication process of herpesviruses. By inhibiting the viral DNA polymerase enzyme, the medication may be part of a management approach for the viral load during active flare-ups or outbreaks, which is a common clinical objective in equine and feline medicine.
Commonly observed responses may include digestive upset, such as vomiting or a lack of interest in food. In some cases, your veterinarian may monitor for more significant shifts in blood cell counts or kidney markers and you should report any signs of unusual lethargy or physical distress to your veterinarian immediately.
