CHARLESTON, S.C. — Once-daily treatment with valacyclovir for the suppression of genital herpes caused by herpes simplex virus type-2 was well-tolerated for up to 20 months in a recent study.
Previously, data were available only for up to 12 months of daily valacyclovir use, Zane A. Brown, M.D., of the University of Washington, Seattle, and his colleagues reported in a poster at the annual meeting of the Infectious Diseases Society for Obstetrics and Gynecology.
For the current study, which was supported by GlaxoSmithKline Inc., 1,484 serodiscordant, heterosexual, monogamous couples were enrolled, and the seropositive partner was randomized to receive either placebo or 500 mg/day of valacyclovir for 8 months.
The results of this double-blind phase, which were previously reported by the investigators, showed that the treatment significantly reduced the risk of genital herpes transmission.
Following the double-blind phase, 1,018 of the 1,484 participants treated in the double-blind phase entered an open-label suppression phase of the study, which provided 12 months of suppressive therapy with 500 mg/day of valacyclovir. Patients in this phase were evaluated every three months for laboratory values and adverse events.
More than 85% of participants who completed the entire 20 months of treatment were at least 80% compliant with the study medication.
During the double-blind and open-label phases, the nature and incidence of adverse events were similar in the 519 participants originally assigned to receive valacyclovir (treatment group) and the 499 originally assigned to receive placebo.
Common adverse events included headache, nasopharyngitis, and upper respiratory tract infection.
Serious adverse events were reported infrequently and were similar in frequency in the treatment group (5% incidence rate) and the placebo group (3% incidence rate).
Only one serious adverse event (gastritis in one patient) during the entire 20-month study was considered by the investigators to be possibly attributable to valacyclovir, and it occurred during the open-label portion of the study.
Adverse events leading to treatment discontinuation occurred in fewer than 1% of those in the treatment group, and in 1% of those in the placebo group; clinically significant laboratory abnormalities occurred in 6% of patients in both groups.
No deaths occurred during the study periods.
Despite a prior lack of data on the safety of valacyclovir for the suppression of genital herpes caused by HSV-2 when used for longer than 12 months, some physicians prescribe such therapy for longer periods, the investigators noted.
These findings suggest that treatment with valacyclovir is as safe for up to 20 months as it is with 8–12 months of suppressive therapy, they concluded.