Daily Therapy Cuts Herpes Transmission Risk

Taking Valtrex Once a Day Reduces Risk of Spreading Herpes

Medically Reviewed by Brunilda Nazario, MD on December 31, 2003
From the WebMD Archives

Dec. 31, 2003 -- People with herpes who take an antiviral drug once a day can reduce the risk of transmitting the virus to their sexual partners by nearly 50%.

A new study shows that daily therapy with the antiviral drug Valtrex significantly lowers the risk of transmitting genital herpes among heterosexual couples in which one partner is infected with the herpes simplex virus type 2 (HSV-2).

Valtrex is commonly used to treat outbreaks of genital herpes, but preliminary results of this study prompted the FDA to approve a second indication for Valtrex in reducing the risk of transmitting the disease to susceptible heterosexual partners. The complete results appear in the Jan. 1, 2004, issue of TheNew England Journal of Medicine.

Valtrex is manufactured in the U.S. by GlaxoSmithKline. GlaxoSmithKline is a WebMD sponsor.

Daily Therapy Helps Prevent Herpes Transmission

In the study, researchers followed 1,484 heterosexual, monogamous couples in which one partner was diagnosed with genital herpes and was experiencing symptoms and the other partner was not. The infected partners were randomly chosen to take either 500 mg of Valtrex or a placebo once a day for eight months.

The couples were counseled on safer-sex practices, such as using condoms during sexual contact and refraining from sexual contact when the infected partner is experiencing symptoms or an outbreak of genital herpes. Sexual transmission to a partner has been shown to occur even when the infected partner has no symptoms.

Researchers found the risk of transmitting the HSV-2 virus from one partner to the other was reduced by 48% in the Valtrex group, and the incidence of symptomatic genital herpes among the partners of those using Valtrex was reduced by 75%. (Not all people infected with the HSV-2 virus go on to develop symptoms.)

The study also showed there was evidence of HSV-2 DNA detected in samples of genital secretions on 2.9% of the days among infected partners who used daily Valtrex therapy compared with 10.8% of the days of those who received the placebo. Daily therapy also reduced the frequency of genital herpes outbreaks among the infected partners.

Results Open Door to HIV Prevention Studies

In an editorial that accompanies the study, Clyde S. Crumpacker, MD, of Beth Israel Deaconess Medical Center in Boston, says these results provide the basis for future studies on whether daily therapy to prevent HSV-2 infection might also reduce the risk of HIV transmission.

Millions could benefit if the use of acyclovir and related drugs, such as Valtrex and Famvir, are proven to decrease the transmission of HIV by preventing HSV-2 genital ulcers, writes Crumpacker. Acyclovir was the first of the drugs used to treat genital herpes, but newer drugs have been developed that can be taken fewer times during the day.

There is a clear association between the prevalence of genital herpes infection and the explosion in heterosexual transmission of HIV, he writes.

Crumpacker writes that generic acyclovir is the cheapest and safest of the antiviral drugs and is unlikely to cause resistance or lose effectiveness with prolonged use.

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SOURCES: Corey, L. TheNew England Journal of Medicine, Jan. 1, 2004; vol 350: pp 11-20. WebMD Medical News: "Valtrex Lowers Herpes Transmission." FDA.

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