Valacyclovir

OBJECTIVE: To discuss the clinical pharmacology, antiviral activity, clinical efficacy, and other therapeutic issues associated with valacyclovir use for the treatment of herpesvirus infections. DATA SOURCE: Literature searches using MEDLINE were prospectively designed to include relevant articles and abstracts between January 1982 and March 1996. The searches focused on valacyclovir pharmacology, clinical efficacy, and issues associated with herpesvirus infections. STUDY SELECTION: Selection of clinical and basic science studies were limited to those focusing on valacyclovir. All articles with pertinent information relevant to the scope of this article were reviewed. DATA SYNTHESIS: Valacyclovir is an amino acid ester prodrug of acyclovir. It is currently approved for die treatment of herpes tester infections in immunocompetent adults (1 g po tid for 7 d) and recurrent episodes of genital herpes in immunocompetent adults (500 mg bid for 5 d), Valacyclovir is rapidly and almost completely hydrolyzed to acyclovir prior to systemic exposure. The bioavailability of valacyclovir is 54% compared to approximately 20% for oral acyclovir. At higher dosages (2 g qid), the plasma AUC of acyclovir following oral valacyclovir administration approximates that seen after intravenous administration of 10 mg/kg every 8 hours, Clinical data indicate that valacyclovir is at least as effective as acyclovir in decreasing the duration of pain associated with postherpetic neuralgia, and in reducing time to genital lesion healing and the length of the episode. CONCLUSIONS: Valacyclovir has improved bioavailability over acyclovir and is at least as efficacious. The favorable safety profile of acyclovir and increased systemic exposure make it a particularly ideal candidate for further studies of herpes group viral infections in immunocompromised patients.