Famciclovir is an antiviral medicine that is used to treat infections caused by herpes viruses, including genital herpes, cold sores, and shingles.

Famciclovir is sometimes used in people with human immunodeficiency virus (HIV) who develop herpes outbreaks around the mouth, genitals, or anal area.

Famciclovir may not be effective in treating your first episode of genital herpes, but may help prevent future episodes. Famciclovir also may not be effective in Black or African-American people with genital herpes, and may not be effective in any person with shingles (herpes zoster) affecting the eyes.

There is no cure for herpes and famciclovir will not prevent you from developing symptoms in the future.

Famciclovir may also be used for purposes not listed in this medication guide.

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Taking more famciclovir than prescribed will not make this medicine more effective

For cold sores or genital herpes, you should start taking famciclovir as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).

You may take famciclovir with or without food.

Lesions caused by herpes viruses should be kept as clean and dry as possible. Wearing loose clothing may help to prevent irritation of the lesions.

To prevent recurrent genital herpes, you may need to take famciclovir for up to 1 year. Follow your doctor's instructions.

Use this medicine for the full prescribed length of time, even if your symptoms quickly improve. Skipping doses may increase the risk of your virus becoming resistant to medication.

Store at room temperature away from moisture and heat.

Usual Adult Dose for Herpes Simplex -- Mucocutaneous/Immunocompetent Host:

Genital herpes:
Initial episode: 250 mg orally 3 times a day for 7 to 10 days has been recommended by the US Centers for Disease Control and Prevention (CDC)

Recurrent episodes: 1000 mg orally twice a day for 1 day; alternatively, 125 mg orally twice a day for 5 days has been recommended by the CDC

Famciclovir should be started at the first sign or symptom of a recurrent episode (such as tingling, burning, itching, pain, or lesion). The efficacy has not been established if started more than 6 hours after onset of symptoms or lesions.

Usual Adult Dose for Herpes Simplex -- Mucocutaneous/Immunocompromised Host:

Recurrent episodes of orolabial or genital herpes in HIV-infected patients: 500 mg orally twice a day for 7 days (5 to 10 days recommended by the CDC)

Famciclovir should be started at the first sign or symptom of a recurrent episode (such as tingling, burning, itching, pain, or lesion). The efficacy has not been established if started more than 48 hours after onset of symptoms or lesions.

Usual Adult Dose for Herpes Simplex -- Suppression:

Chronic suppression of recurrent genital herpes:
Immunocompetent patients: 250 mg orally twice a day
HIV-infected patients: 500 mg orally twice a day has been recommended by the CDC

Therapy should be continued as clinically appropriate, although the safety and efficacy of famciclovir therapy beyond 1 year have not been established.

Usual Adult Dose for Herpes Zoster:

500 mg orally every 8 hours for 7 days

Famciclovir is most effective if started within 48 hours of onset of rash. The efficacy has not been established if started more than 72 hours after onset of rash.

Usual Adult Dose for Herpes Simplex Labialis:

Recurrent herpes labialis: 1500 mg orally as a single dose

Famciclovir is most effective if started at the earliest sign or symptom of a cold sore (such as tingling, burning, itching, pain, or lesion).

You should not use famciclovir if you are allergic to famciclovir or penciclovir cream (Denavir).

Tell your doctor if you have ever had:

• liver disease;

• kidney disease;

• a weak immune system;

• galactose intolerance;

• severe lactase deficiency; or

• glucose-galactose malabsorption.

Tell your doctor if you are pregnant or plan to become pregnant. Herpes can be passed to your baby during childbirth if you have a genital lesion when your baby is born. If you have genital herpes, it is very important to prevent herpes lesions during pregnancy. Take your medicine as directed to best control your infection.

If you are pregnant, your name may be listed on a pregnancy registry to track the effects of famciclovir on the baby.

It may not be safe to breast-feed while using this medicine. Ask your doctor about any risk.

Famciclovir is not approved for use by anyone younger than 18 years old.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

Unless your doctor tells you otherwise, continue your normal diet.

Taking famciclovir will not prevent you from passing genital herpes to other people. Herpes infections are contagious and you can infect other people even while you are taking famciclovir.

Avoid driving or hazardous activity until you know how this medicine will affect you. Your reactions could be impaired.

Avoid sexual intercourse or use a latex condom to help keep you from spreading the virus to others. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent the spread of infection.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Famciclovir may cause serious side effects. Call your doctor at once if you have:

• confusion; or

• kidney problems--little or no urination, swelling in your feet or ankles, feeling tired or short of breath.

Common side effects of famciclovir may include:

• headache; or

• nausea.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Other drugs may affect famciclovir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests to check your response to famciclovir.

Do not have sexual intercourse when you are having an outbreak of genital herpes. However, genital herpes can be spread to others, even when you do not have symptoms.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription. If you still have symptoms of infection after you finish the famciclovir, call your doctor.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.