Suppressive drug therapy hinders herpes. (Biomedicine).

A daily regimen of the antiviral drug valacyclovir controls genital herpes vastly better than does the same medication when used only to treat outbreaks of the disease, according to a new study.

To compare the effectiveness of the two approaches, scientists identified 66 people who averaged four to nine genital herpes recurrences per year. The researchers randomly assigned 34 people to take valacyclovir every day and 32 to take it for 5 days upon the first sign of a herpes episode. Doctors call the first approach suppressive therapy and the second, episodic therapy.

After 1 year, people taking the pills daily averaged 1.6 genital herpes recurrences, whereas those taking them only to treat outbreaks averaged 7.3 such episodes, reports Kenneth F. Fife, a virologist at Indiana University School of Medicine in Indianapolis. Moreover, the people getting suppressive therapy averaged 180 days between episodes, in contrast to average diseasefree intervals of 53 days among the people getting valacyclovir only at each outbreak, he says.

There has been no consensus among physicians as to whether suppressive or episodic treatment works best against genital herpes, also called herpes simplex 2, Fife says.

"It's taken physicians a while just to get used to [prescribing] antiviral therapy for genital herpes," he says. Judging from this study, Fife concludes, "suppressive therapy is clearly the way to go."

Valacyclovir is converted in the intestines to acyclovir, the active antiviral agent. Whereas acyclovir pills are absorbed poorly, valacyclovir delivers more of the active drug to the bloodstream.

The suppressive therapy is also likely to work against herpes simplex 1, the form of herpes that shows up as cold sores, says Fife. Lab tests show that herpes simplex 1 is more sensitive to acyclovir than is herpes simplex 2, says Fife.

Both herpes viruses hide in the body's nerves and periodically make forays out to the skin, where they cause painful blisters.

A study in the 1980s, in which people took acyclovir pills daily for 6 years, showed no signs of the virus becoming resistant to the drug, Fife says. --N.S.