Acyclovir for Herpes

Treatment of acute genital herpes outbreaks

Acyclovir significantly reduces the duration and severity of initial (first-episode) genital herpes. It reduces the duration of viral shedding, lesion healing, and pain. Sometimes, acyclovir decreases new lesion formation and prevents the development of vesicles.

Genital herpes can be treated by topical, oral or intravenous acyclovir depending on stage and severity of disease. Topical acyclovir is totally ineffective for reurrent outbreaks.

Dosage for first-episode genital herpes: 200 mg every 4 hours while awake (5 times/day) for 10 days. Alternatively, 400 mg 3 times/day for 5-10 days.

Almost all persons with symptomatic initial genital herpes subsequently experience recurrences of genital lesions. Acyclovir can be used episodically to shorten the duration of recurrent outbreaks of genital herpes.

Dosage for reurrent herpes: 200 mg every 4 hours while awake (5 times/day) for 5 days. Alternatively, 400 mg 3 times/day for 5 days.

The research data suggests, that 800 mg 3 times per day for 2 days is also very effective course3. A 2-day course reduces the duration of lesions by 2 days (4 days on acyclovir versus 6 days on placebo) and viral shedding by 1 day (25 hours on acyclovir versus 58.5 hours on placebo).

Suppressive therapy

Acyclovir can be used continuously as suppressive therapy to reduce the frequency of outbreaks and possibly decrease the risk of HSV transmission to a partner.

Acyclovir suppressive therapy reduces the frequency of genital herpes recurrences by 70% to 80% among persons with frequent recurrences (more than 6 recurrences per year). About 50% of persons have no symptomatic outbreaks during the year1. Moreover, more than 20% of persons stay recurrence free during 5 years of continuous acyclovir use2.

Acyclovir therapy during the final month of pregnancy may prevent the perinatal HSV infection and the need for C-section.

Dosage for suppressive therapy: 400 mg twice daily or 200 mg 3-5 times/day, for up to 12 months followed by re-evaluation.

Long-term acyclovir suppressive therapy of genital herpes has been used safely for up to 10 years4.

Important note: Acyclovir does not cure the herpes virus or eliminates its transmission.

See also


  • 1. Kaplowitz LG, Baker D, Gelb L, Blythe J, et al. Prolonged continuous acyclovir treatment of normal adults with frequently recurring genital herpes simplex virus infection. JAMA. 1991 Feb 13;265(6):747-51.
  • 2. Goldberg LH, Kaufman R, Kurtz TO, Conant MA, Eron LJ, Batenhorst RL, Boone GS. Long-term suppression of recurrent genital herpes with acyclovir. Arch Dermatol. 1993 May;129(5):582-7.
  • 3. Wald A, Carrell D, Remington M, Kexel E, Zeh J, Corey L. Two-day regimen of acyclovir for treatment of recurrent genital herpes simplex virus type 2 infection. Clin Infect Dis. 2002 Apr 1;34(7):944-8. PubMed
  • 4. Tyring SK, Baker D, Snowden W. Valacyclovir for herpes simplex virus infection: long-term safety and sustained efficacy after 20 years' experience with acyclovir. J Infect Dis. 2002 Oct 15;186 Suppl 1:S40-6. PubMed

Author: OriginalDrugs Team
Last reviewed: May, 2015

Quick facts


  • How does acyclovir work?
    Acyclovir is inactive until thymidine kinase enzyme of herpesvirus turns it into acyclovir triphosphate, which inhibits viral DNA polymerase to cause chain termination. So, it works only in infected cells.