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Antiviral Medicines for Genital Herpes


Generic Name Brand Name
acyclovir Zovirax
famciclovir Famvir
valacyclovir Valtrex

Acyclovir, famciclovir, and valacyclovir are antiviral medicines used to treat genital herpes. All are effective. But because valacyclovir and famciclovir are absorbed better by the stomach, they can be taken less often than acyclovir. Antiviral medicines are usually taken by mouth (orally). But they are sometimes given intravenously (IV) in severe genital herpes outbreaks or herpes in newborns.

The topical form of acyclovir (Zovirax ointment) offers little benefit in the treatment of genital herpes and is not recommended.

How It Works

Antiviral medicines stop the growth of the herpes simplex virus (HSV).

Why It Is Used

Antiviral medicines may be given to:

  • People who are having a primary outbreak of genital herpes.
  • People who have frequent (about 6 or more a year) recurrent outbreaks of genital herpes.
  • People who want to decrease the length and severity of their recurrent outbreaks.
  • People who want to decrease the possibility of unintentionally transmitting the virus. Genital herpes is more likely to be transmitted during the first year of infection, even though a person may not have symptoms of a genital herpes outbreak.
  • Pregnant women who are having an outbreak of genital herpes.
  • Women in the last 4 weeks of pregnancy.
  • People who have impaired immune systems and recurrent outbreaks.

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.

Side Effects

All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

  • Usually the benefits of the medicine are more important than any minor side effects.
  • Side effects may go away after you take the medicine for a while.
  • If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

Call911or other emergency services right away if you have:

Call your doctor right away if you have:

  • Dizziness or if you are feeling faint.
  • A fast heartbeat.
  • Confusion.
  • A change in vision.

Common side effects of this medicine include:

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.

Advice for women

If you are pregnant, breast-feeding, or planning to get pregnant, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. And make sure that all your doctors know that you are pregnant, breast-feeding, or planning to get pregnant.


Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.


  1. Centers for Disease Control and Prevention (2010). Genital HSV infections section of Sexually transmitted diseases treatment guidelines, 2010. MMWR, 59(RR-12): 20–25. Also available online:

  2. Hollier LM, Straub H (2011). Genital herpes, search date January 2010. BMJ Clinical Evidence. Available online:

By Healthwise Staff
Primary Medical Reviewer Sarah Marshall, MD - Family Medicine
Specialist Medical Reviewer Jeanne Marrazzo, MD, MPH - Infectious Disease
Current as of December 20, 2012

WebMD Medical Reference from Healthwise

Last Updated: December 20, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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