Acyclovir for Herpes

• Generic name: Acyclovir (Acycloguanosine)
• Trade names: Zovirax
• Pharmacologic category: Antiviral agent, Nucleoside analogue
• FDA approved: 1982
• Pregnancy risk factor: B

Acyclovir, the first of the nucleoside analogues, was discovered by a team led by Gertrude B. Elion in the late 1970s. It is a synthetic purine analogue active against herpes simplex viruses HSV-1 and HSV-2, and varicella-zoster.

Acyclovir is used to treat genital herpes simplex virus, herpes labialis (cold sores), herpes zoster (shingles), HSV encephalitis, neonatal HSV, mucocutaneous HSV in immunocompromised patients, and varicella-zoster (chickenpox).

Acyclovir cannot eradicate the latent viral reservoir and does not cure herpes infection. But it may relieve the symptoms of viral infection, shorten the duration of an outbreak and virus shedding period.

Acyclovir acts only during active viral replication, which largely precedes visible blisters, and thus it has most benefits if begun during prodromal stage.

• Elimination half-life: 2.5 to 3.3 hr
• Metabolism: Converted by viral enzymes to acyclovir monophosphate, and further converted to diphosphate then triphosphate (active form) by cellular enzymes
• Excretion: Urine (62% to 90% as unchanged drug and metabolite)

• lower price compared to newer antiviral agents
• suppresses asymptomatic viral shedding [9]
• safe and extremely well-tolerated by most patients [1]. Toxicity is rare, but in persons who are dehydrated or who have poor renal function, acyclovir can crystallize in the renal tubules, leading to a reversible creatinine elevation.
• high efficacy [5]
• can reduce asymptomatic viral shedding by 80%

• requires frequent dosing regimen
• does not cure the viral infection

• Posttransplantation cytomegalovirus (CMV) infection [2-3]
• Posttransplantation HSV infection [11, 12]
• Ocular herpes simplex virus infection [4]
• Infectious mononucleosis [6, 7]
• Herpes zoster ophthalmicus [8]
• Varicella pneumonia [10]

Acyclovir prevents the growth and multiplication of the herpes virus. It can insert itself into virus DNA during virus replication.

Acyclovir is selectively phosphorylated only within virus-infected cells by viral thymidine kinase (TK). Further phosphorylation by cellular enzymes leads to the production of acyclovir triphosphate, which competes with the natural nucleotide, dGTP, resulting in the selective inhibition of viral DNA polymerase. Incorporation of the analogue triphosphate into the growing DNA chain prevents continued extension of the DNA chain.

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• 1. Girard M. Safety of acyclovir in general practice: a review of the literature. Pharmacoepidemiol Drug Saf. 1996 Sep;5(5):325-32.
• 2. Flechner SM, Avery RK, Fisher R, Mastroianni BA, Papajcik DA, O'Malley KJ, Goormastic M, Goldfarb DA, Modlin CS, Novick AC. A randomized prospective controlled trial of oral acyclovir versus oral ganciclovir for cytomegalovirus prophylaxis in kidney transplant recipients. Transplantation. 1998 Dec 27;66(12):1682-8.
• 3. Winston DJ, Wirin D, Shaked A, Busuttil RW. Randomised comparison of ganciclovir and acyclovir for long-term cytomegalovirus prophylaxis in liver-transplant recipients. Lancet. 1995 Jul 8;346(8967):69-74.
• 4. Uchoa UB, Rezende RA, Carrasco MA, Rapuano CJ, Laibson PR, Cohen EJ. Long-term acyclovir use to prevent recurrent ocular herpes simplex virus infection. Arch Ophthalmol. 2003 Dec;121(12):1702-4.
• 5. Tyring SK, Douglas JM, Corey L, Spruance SL, Esmann J. A randomized, placebo-controlled comparison of oral valacyclovir and acyclovir in immunocompetent patients with recurrent genital herpes infections. Arch Dermatol. 1998 Feb;134(2):185-91.
• 6. Andersson J, Britton S, Ernberg I, Andersson U, Henle W, Skoldenberg B, Tisell A. Effect of acyclovir on infectious mononucleosis: a double-blind, placebo-controlled study. J Infect Dis. 1986 Feb;153(2):283-90.
• 7. Ernberg I, Andersson J. Acyclovir efficiently inhibits oropharyngeal excretion of Epstein-Barr virus in patients with acute infectious mononucleosis. J Gen Virol. 1986 Oct;67 ( Pt 10):2267-72.
• 8. Hoang-Xuan T, Buchi ER, Herbort CP, Denis J, Frot P, Thenault S, Pouliquen Y. Oral acyclovir for herpes zoster ophthalmicus. Ophthalmology. 1992 Jul;99(7):1062-70; discussion 1070-1.
• 9. Wald A, Zeh J, Barnum G, Davis LG, Corey L. Suppression of subclinical shedding of herpes simplex virus type 2 with acyclovir. Annals Internal Medicine. 1996 Jan 1;124(1 Pt 1):8-15
• 10. Smego RA, Asperilla MO. Use of acyclovir for varicella pneumonia during pregnancy. Obstet Gynecol. 1991 Dec;78(6):1112-6.
• 11. Gluckman E, Lotsberg J, Devergie A, Zhao XM, Melo R, Gomez-Morales M, Mazeron MC, Perol Y. Oral acyclovir for prophylaxis of herpes simplex infection after bone marrow transplantation. J Antimicrob Chemother. 1983 Sep;12 Suppl B:161-7
• 12. Seale L, Jones CJ, Kathpalia S, Jackson GG, Mozes M, Maddux MS, Packham D. Prevention of herpesvirus infections in renal allograft recipients by oral acyclovir. JAMA. 1985 Dec 27;254(24):3435-8.

Last modified: July, 2011