How Well It Works

Initial outbreak

Antiviral medicines may significantly reduce the severity of an outbreak of genital herpes and decrease the time it takes an outbreak to heal. The medicine also decreases the number of days of painful symptoms. And for some people, this medicine decreases the number of days you can spread the virus.

The amount and how often you take antivirals depends on the specific antiviral and whether you are taking them for a primary outbreak, recurrent outbreak, or for suppressive therapy.

Recurrent outbreaks

Antiviral medicine is most effective if you take it when you first notice the prodromal symptoms (tingling and pain) of a recurrent genital herpes outbreak and if you take it for the next 5 to 7 days or until symptoms go away.

Some people with frequent recurrent outbreaks (more than 6 a year) take antiviral medicine every day (suppressive therapy) to help reduce the frequency and duration of the outbreaks. Antiviral medicine can reduce the number of outbreaks by 70% to 80%.¹

Suppressive therapy

Research shows that an HSV-infected person in a heterosexual, single-partner (monogamous) relationship who takes valacyclovir daily in the doses used for suppressive therapy to prevent recurrent outbreaks reduces the risk of infecting his or her partner.² Other antiviral medicines may also reduce transmission, but further study is needed.

Treatment during pregnancy

The CDC has published guidelines about the use of antiviral medicines in pregnancy.¹

• Oral acyclovir may be given to pregnant women for a primary HSV infection or for severe recurrent outbreaks.
• Oral acyclovir may be given to pregnant women at any time during the pregnancy, including the first trimester.
• Acyclovir may be given intravenously (IV) to pregnant women who have a severe HSV infection.
• Acyclovir may decrease the frequency of recurrent outbreaks in pregnant women close to delivery, thereby reducing the possibility of needing a cesarean section at the time of delivery.

If a genital herpes blister or sore is present at the time of labor and delivery, a cesarean section is usually done. A cesarean section may be recommended if a woman suspects she has symptoms of an impending outbreak, such as tingling or pain (prodromal symptoms). For women who have recurrent outbreaks, acyclovir used in the last 4 weeks of pregnancy may reduce the need for a cesarean section by reducing the risk of an outbreak at the time of delivery.

People with human immunodeficiency virus (HIV) should talk with their doctors for advice about these medicines. Depending on the stage of their illness, they may need higher doses or longer treatment time with antiviral medicines.