For many patients with a history of genital herpes (herpes simplex virus type 2), suppressive antiviral therapy is required in addition to aggressive treatment of active disease. The antiviral agent valacyclovir is metabolized to acyclovir after oral administration, with acyclovir bioavailability that is three to five times that observed with the drug acyclovir. This high bioavailability allows therapeutic concentrations with once-daily dosing. Baker and colleagues evaluated the ability of daily valacyclovir therapy in a dosage of 500 mg to prevent recurrent symptomatic outbreaks of genital herpes.

The one-year study included 126 adults who had culture-proven recurrent genital herpes infection. The mean age of the 46 women and 80 men was 46 years. Patients were instructed to increase the once-daily, 500-mg dose of valacyclovir to twice daily administration for five days if they developed symptoms of recurrence. Symptoms related to herpes infection, other clinical conditions and adverse effects were recorded in diaries. Patients were evaluated every three months.

The full year of treatment was completed by 116 patients, and over 80 percent took all of the valacyclovir doses as instructed. No recurrences during the entire year were reported by 84 (67 percent) of the 126 subjects eligible for evaluation. The recurrence-free rates remained high and rose during the study. Recurrence-free rates for the first, second, third and fourth quarters were 81, 84, 84 and 91 percent, respectively.

Recurrence rates were similar in women and men. Only 12 (11 percent) of 107 recurrences followed one or more missed doses in the previous five days.

Laboratory values showed no biochemical or hematologic changes during the study. Headache was reported by 16 patients (13 percent), rhinitis by 12 patients (9 percent), sinusitis by 10 patients (8 percent) and bronchitis by seven patients (6 percent). None of the adverse events was considered to be related to the drug.

The authors conclude that 500 mg of valacyclovir daily suppresses clinical episodes of genital herpes infection. Patients tolerated the medication well and achieved high rates of compliance.