Valaciclovir. A review of its antiviral activity, pharmacokinetic properties and therapeutic efficacy in herpesvirus infections.
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.
Perry
C M
CM
Adis International Limited, Auckland, New Zealand.
Faulds
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D000212:Acyclovir / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use; D000328:Adult; D000818:Animals; D000998:Antiviral Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use*; D004352:Drug Resistance, Microbial; D004361:Drug Tolerance; D006558:Herpes Genitalis / Q000188:drug therapy; D006562:Herpes Zoster / Q000188:drug therapy; D006564:Herpesviridae / Q000187:drug effects; D006566:Herpesviridae Infections / Q000188:drug therapy*; D006801:Humans; D008875:Middle Aged; D012008:Recurrence; D000077483:Valacyclovir; D014633:Valine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use
D000998:Antiviral Agents; D014633:Valine; D000077483:Valacyclovir; D000212:Acyclovir