Valaciclovir. A review of its antiviral activity, pharmacokinetic properties and therapeutic efficacy in herpesvirus infections

Drugs. 1996 Nov;52(5):754-72. doi: 10.2165/00003495-199652050-00009.


Valaciclovir, the L-valyl ester of aciclovir (acyclovir), is an oral prodrug that undergoes rapid and extensive first-pass metabolism to yield aciclovir and the essential amino acid L-valine. Aciclovir, the active antiviral component of valaciclovir, shows good in vitro activity against the herpesviruses herpes simplex virus (HSV)-1, HSV-2 and varicella zoster virus. The bioavailability of aciclovir from oral valaciclovir is considerably greater than that achieved after oral aciclovir administration. Thus, valaciclovir delivers therapeutic aciclovir concentrations when administered in a less frequent oral dosage regimen than is required for aciclovir. Valaciclovir is an effective treatment for herpes zoster in immunocompetent adults. In a large comparative study that included patients > or = 50 years of age, valaciclovir (1000mg 3 times daily for 7 or 14 days) and oral aciclovir (800mg 5 times daily) were equally effective in achieving resolution of cutaneous zoster lesions. Importantly, valaciclovir was significantly more effective than aciclovir in reducing the duration of zoster-associated pain. Preliminary results of several studies indicate that valaciclovir (500 to 1000mg twice daily for 5 to 10 days) is as effective as aciclovir (200mg 5 times a day for 5 to 10 days) in the treatment of genital herpes. In patients with first or recurrent episodes of genital herpes, valaciclovir reduced the duration of viral shedding, hastened lesion healing and decreased lesion-associated pain. Valaciclovir was also effective in suppressing recurrent episodes of genital herpes and significantly prolonged the time to a recurrent episode of infection compared with placebo. Valaciclovir is a well tolerated drug; in herpes zoster and HSV studies its tolerability profile was similar to that of aciclovir or placebo. Valaciclovir represents and advance in antiherpes drug therapy and is a useful treatment option for patients with herpes zoster or genital herpes. It is at least as effective as aciclovir and is administered in a more convenient oral dosage regimen. Thus, valaciclovir may ultimately succeed aciclovir as a first-line treatment for genital herpes or herpes zoster.

Publication types

  • Review

MeSH terms

  • Acyclovir / administration & dosage
  • Acyclovir / analogs & derivatives*
  • Acyclovir / pharmacokinetics
  • Acyclovir / pharmacology
  • Acyclovir / therapeutic use
  • Adult
  • Animals
  • Antiviral Agents / administration & dosage
  • Antiviral Agents / pharmacokinetics
  • Antiviral Agents / pharmacology
  • Antiviral Agents / therapeutic use*
  • Drug Resistance, Microbial
  • Drug Tolerance
  • Herpes Genitalis / drug therapy
  • Herpes Zoster / drug therapy
  • Herpesviridae / drug effects
  • Herpesviridae Infections / drug therapy*
  • Humans
  • Middle Aged
  • Recurrence
  • Valacyclovir
  • Valine / administration & dosage
  • Valine / analogs & derivatives*
  • Valine / pharmacokinetics
  • Valine / pharmacology
  • Valine / therapeutic use


  • Antiviral Agents
  • Valine
  • Valacyclovir
  • Acyclovir