medicationsacyclovir

Acyclovir is an antiviral medication used to treat infections caused by herpes simplex virus (HSV-1 and HSV-2) and varicella-zoster virus (VZV). It is a nucleoside analog activated by viral thymidine kinase, then inhibits viral DNA polymerase and limits replication in infected cells.

It is available in oral, intravenous, and topical forms. Indications include treatment of initial and recurrent mucocutaneous herpes simplex infections, suppression for recurrent genital herpes, and treatment of varicella and herpes zoster.

Dosing depends on indication and patient factors. Common regimens include oral 200–400 mg five times daily or 400 mg three times daily for genital herpes; 800 mg five times daily for shingles or varicella; and 10 mg/kg every eight hours intravenously for severe infections.

Oral bioavailability is about 10–20%, and most drug is excreted unchanged by the kidneys, requiring dose adjustment in renal impairment. The drug has a short distribution phase and penetrates skin, nervous tissue, and mucous membranes.

Common adverse effects include nausea, diarrhea, and headache. Intravenous use may cause phlebitis or nephrotoxicity, especially with rapid infusion or dehydration. Caution is advised in kidney disease; use in pregnancy is generally considered safe when clearly indicated, and breastfeeding should be discussed with a clinician.

Acyclovir reduces the duration and severity of herpes lesions and viral shedding but does not cure infection. Resistance can occur in immunocompromised patients through mutations in viral thymidine kinase or DNA polymerase.