Last reviewed 2026-04-21 · How we verify

Acyclovir (ACV)

Acyclovir is a nucleoside analog that inhibits viral DNA polymerase, preventing replication of herpes simplex virus and varicella-zoster virus.

Acyclovir is a nucleoside analog that inhibits viral DNA polymerase, preventing replication of herpes simplex virus and varicella-zoster virus. Used for Herpes simplex virus (HSV-1 and HSV-2) infection, Varicella-zoster virus (chickenpox and shingles) infection, Cytomegalovirus (CMV) infection prophylaxis in immunocompromised patients.

At a glance

Mechanism of action

Acyclovir is phosphorylated by viral thymidine kinase to its active form, which then inhibits viral DNA polymerase and causes chain termination of viral DNA synthesis. This selective toxicity occurs because the drug is preferentially activated in infected cells and has higher affinity for viral DNA polymerase than host cell polymerase.

Approved indications

• Herpes simplex virus (HSV-1 and HSV-2) infection
• Varicella-zoster virus (chickenpox and shingles) infection
• Cytomegalovirus (CMV) infection prophylaxis in immunocompromised patients

Common side effects

• Headache
• Nausea
• Vomiting
• Diarrhea
• Nephrotoxicity (with rapid IV infusion)
• Neurotoxicity (confusion, hallucinations, tremors)

Key clinical trials

• Prevention of Recurrence of Herpes Simplex in Autoimmune Rheumatic Diseases (PHASE4)
• Letermovir Versus Valganciclovir to Prevent Human Cytomegalovirus Disease in Kidney Transplant Recipients (MK-8228-002) (PHASE3)
• A Study of Zidovudine Plus Acyclovir in HIV-Infected Patients (PHASE1)
• Anti-Herpetic Treatment of Genital Ulcer : Effect on HIV & Herpes Shedding (ANRS 1212) (PHASE2)
• Treatment and Suppression of Hairy Leukoplakia in ARC Patients With Oral Acyclovir (ACV) (NA)

Primary sources

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