Acyclovir (Zovirax) was approved for the treatment of herpesvirus infections 
almost two decades ago. It was the first agent in a novel group of antiviral 
medications that now include valacyclovir (Valtrex), penciclovir (Denavir and 
famciclovir (Famvir). These agents have made a dramatic impact on the morbidity 
associated with herpes simplex virus infections and herpes zoster. Topical and 
oral antiviral use have shown modest but statistically significant efficacy in 
treating herpes labialis with most studies demonstrating a significant reduction 
in episode length and/or healing time. Oral acyclovir, valacyclovir and 
famciclovir are efficacious and safe for the treatment of the first episode and 
recurrent genital herpes and are useful as suppressive therapy for individuals 
with frequent genital herpes recurrences. In addition, high doses of oral 
acyclovir, valacyclovir and famciclovir have been shown to speed the healing of 
herpes zoster, and data suggests that these agents also decrease associated 
acute and chronic pain in people of 50 years of age or older. Further research 
is required to clarify the safety of these agents in pregnant women with genital 
herpes, the role of antiviral therapy in decreasing the sexual transmission of 
genital herpes, and the efficacy and cost-effectiveness of these agents in 
treating herpes zoster in people below the age of 50 years.