Primary Uses of Acyclovir
Acyclovir is an antiviral medication primarily used to treat infections caused by herpes viruses, including herpes simplex virus (HSV) types 1 and 2, and varicella-zoster virus (VZV). It shortens outbreak duration and reduces severity for conditions like cold sores (HSV-1), genital herpes (HSV-2), chickenpox (VZV), and shingles (VZV reactivation).[1][2]
How Acyclovir Works Against These Infections
Acyclovir targets viral DNA replication by mimicking guanosine, a DNA building block. Once activated inside virus-infected cells, it halts DNA polymerase activity specific to herpes viruses, sparing most healthy cells. It's most effective when started early in infection.[1][3]
Common Treatment Scenarios
- Cold sores and genital herpes: Oral tablets or topical cream for initial outbreaks or recurrent episodes; suppresses frequent recurrences with daily dosing.
- Chickenpox: Oral form in children and adults to lessen symptoms.
- Shingles: Oral or IV for pain relief and faster rash healing, especially in older patients or immunocompromised individuals.
- Herpes encephalitis or neonatal herpes: Intravenous for severe cases.[2][4]
Who Typically Needs It and Dosing Basics
Prescribed for acute outbreaks, suppression in frequent cases, or prophylaxis in high-risk groups like transplant patients or those with HIV. Standard oral dose is 200-800 mg 2-5 times daily, adjusted for kidney function; IV for hospitalized cases.[1][3]
Limitations and When It's Not Used
Does not cure herpes infections—viruses remain latent—or prevent transmission. Ineffective against non-herpes viruses like influenza or common cold. Resistance can develop in immunocompromised patients with prolonged use.[2][4]
Alternatives If Acyclovir Isn't Suitable
Valacyclovir (prodrug of acyclovir, better absorbed) or famciclovir offer similar efficacy with less frequent dosing. For resistant strains, foscarnet or cidofovir may be used.[3]
[1]: FDA Label for Acyclovir (Zovirax)
[2]: CDC Herpes Treatment Guidelines
[3]: Medscape Acyclovir Overview
[4]: UpToDate: Acyclovir Use in Herpes Infections