Long-term suppressive therapy with acyclovir for recurrent genital herpes

To review the long-term safety and efficacy profile of daily oral acyclovir for the treatment of recurrent genital herpes, this report describes the results from an ongoing clinical trial of more than 1100 immunocompetent individuals with a history of frequently recurring genital herpes. During the first year patients were randomized to receive either 400 mg acyclovir twice daily or placebo. Thereafter, patients received open-label acyclovir suppressive therapy. Complete data are available for 389 of the 430 patients who began the fifth year of study. The percentage of patients who were free of recurrence for any quarter of the fifth year ranged from 85 to 90%. The mean annual number of recurrences per patient declined from 12.9 to 1.7 during the first year of suppressive therapy to 0.8 during the fifth year. More than 20% of the patients receiving suppressive therapy for the entire 5-year period have been recurrence-free. The 50% effective dose (ED50) values for a population of herpes simplex virus clinical isolates before acyclovir treatment were compared with the values determined for isolates recovered at the first episode of recurrent disease after cessation of therapy, from patients in this study who had received up to 6 years of suppressive acyclovir therapy. Resistance of herpes simplex virus to acyclovir was not observed. This study extends the safety and efficacy profile of oral acyclovir in the suppression of genital herpes to 5 years.