Valacyclovir, a widely prescribed antiviral, recently received approval for an expanded indication: suppressive therapy in immunocompetent individuals with genital herpes to reduce the risk of heterosexual transmission to susceptible partners.

Efficacy. An 8-month double-blind, placebo-controlled study was conducted to evaluate the transmission of genital herpes in 1,484 monogamous, heterosexual, immunocompetent couples. The couples were discordant for HSV-2 infection, and the source partner had a history of <9 genital herpes episodes per year. The partners were advised on safer sex practices and advised to use condoms throughout the study period. Source partners were randomized to treatment with either 500 mg of valacyclovir or placebo once daily. Overall HSV-2 acquisition in susceptible partners was defined as symptomatic acquisition of HSV-2 and/or HSV-2 seroconversion. Overall HSV-2 acquisition occurred in 14 (1.9%) susceptible partners in the valacyclovir group compared to 27 (3.6%) in the placebo group. Symptomatic HSV-2 acquisition occurred in 4 (0.5%) and 16 (2.2%) of the susceptible partners in the valacyclovir and placebo groups, respectively. HSV-2 seroconversion occurred in 12 (1.6%) and 24 (3.2%) of the susceptible partners in the valacyclovir and placebo groups, respectively. These results represent risk reductions of 48% (overall), 75% (symptomatic), and 50% (seroconversion) for HSV-2 acquisition in susceptible individuals whose partners were randomized to valacyclovir instead of placebo.

Safety. Because valacyclovir is not a cure for genital herpes, patients should be counseled to use safer sex practices in combination with suppressive therapy with the drug. Dosage reduction is advised when administering valacyclovir to patients with renal impairment. Inappropriately high doses of valacyclovir in these patients have resulted in reports of acute renal failure and central nervous system symptoms. The most common adverse effects associated with the administration of valacyclovir in patients for the reduction of genital herpes transmission include headache, nasopharyngitis, and upper respiratory tract infection.

Dosing. For the reduction of transmission of genital herpes in patients with a history of <9 recurrences per year, the recommended dose of valacyclovir is 500 mg once daily for the source partner.