Objective: To discuss the antiviral activity, pharmacokinetics, clinical efficacy, and adverse effect profile of famciclovir, the oral prodrug of penciclovir (PCV), and to compare these features of famciclovir with those of acyclovir in the treatment of herpesvirus infections.
Data sources: Literature was identified by MEDLINE search, and abstracts from recent meetings were included where relevant. Data provided by the manufacturer were also used.
Study selection: Data regarding antiviral activity were included if accepted and widely used methods were followed. Clinical trials in which a comparison with acyclovir or placebo was performed were given the highest priority.
Data synthesis: In comparison with acyclovir, PCV has similar antiviral activity although its mode of action is not identical. When administered orally, faMciclovir, the oral prodrug of PCV, is better absorbed than acyclovir, yielding an absolute bioavailability of PCV of 77%. The predominant route of PCV elimination is via the kidneys, with a half-life of approximately 2.5 hours. In trials comparing famciclovir with acyclovir for the treatment of herpes zoster in immunocompetent individuals, comparable results were obtained. Famciclovir is also effective as therapy for recurrent episodes of genital herpes and may prove useful for chronic suppressive therapy. The most common adverse effects of famciclovir are headache and gastrointestinal upset. The dosage of famciclovir for herpes zoster in immunocompetent individuals is 500 mg po tid for 7 days; for recurrent genital herpes a dosage of 125 mg po bid for 5 days is recommended. Dosage adjustments are necessary in patients with renal dysfunction.
Conclusions: Given its comparable efficacy, similar adverse effect profile, and less frequent dosing schedule than acyclovir, famciclovir represents a viable alternative for treatment of herpes zoster and for episodic therapy of recurrent genital herpes in immunocompetent adults. Specific recommendations for other uses of famciclovir await the publication of recent clinical trial results.