Valacyclovir and acyclovir for suppression of shedding of herpes simplex virus in the genital tract.

BACKGROUND: Valacyclovir exhibits better oral absorption and higher, more prolonged serum concentrations than oral acyclovir. The efficacy of valacyclovir and acyclovir on genital herpes simplex virus (HSV) shedding was assessed in a double-blind, 3-period crossover trial.

METHODS: Sixty-nine immunocompetent participants with genital HSV-2 received oral valacyclovir, acyclovir, and matching placebo in random order for 7-week periods. Participants provided daily genital mucosal swabs for HSV detection by viral culture and polymerase chain reaction (PCR).

RESULTS: HSV was detected at least once in 62 (90%) participants by culture and in 68 (98%) by PCR. During placebo, the total HSV shedding rate was 15.4% of days by culture (PCR, 40.2%); the subclinical shedding rate was 6.6% by culture (PCR, 27.1%). Both antivirals were associated with lower HSV shedding by culture (relative risk [RR], 0.03 [95% confidence interval [CI], 0.01-0.07] for valacyclovir and RR, 0.05 [95% CI, 0.03-0.10] for acyclovir) and PCR (RR, 0.18 [95% CI, 0.12-0.26] for valacyclovir and RR, 0.20 [95% CI, 0.15-0.28] for acyclovir), compared with placebo. No significant differences in frequency and quantity of HSV were detected by PCR between the valacyclovir and acyclovir arms.

CONCLUSIONS: Although the suppression of viral replication is not complete, valacyclovir and acyclovir are highly effective in suppressing the frequency and quantity of genital HSV shedding.