Famciclovir is used to treat herpes zoster (shingles; a rash that can occur in people who have had chickenpox in the past). It is also used to treat repeat outbreaks of herpes virus cold sores or fever blisters in people with a normal immune system. Famciclovir is used to treat repeat outbreaks and to prevent further outbreaks of genital herpes (a herpes virus infection that causes sores to form around the genitals and rectum from time to time) in people with a normal immune system. Famciclovir is also used to treat returning herpes simplex infections of the skin and mucous membranes (mouth, anus) in people with human immunodeficiency virus (HIV) infection. Famciclovir is in a class of medications called antivirals. It works by stopping the spread of the herpes virus in the body. Famciclovir does not cure herpes infections and may not stop the spread of herpes virus to other people. However, it may decrease the symptoms of pain, burning, tingling, tenderness, and itching; help sores to heal; and prevent new sores from forming.

Famciclovir comes as a tablet to take by mouth with or without food. When famciclovir is used to treat shingles, it is usually taken every 8 hours (three times a day) for 7 days, starting within 3 days after the rash begins to appear. When famciclovir is used to treat cold sores and fever blisters, it is usually taken as one dose at the earliest sign or symptom (tingling, itching, or burning) of a cold sore. When famciclovir is used to treat repeat outbreaks of genital herpes, it is usually taken twice a day for one day, starting within 6 hours of the first sign or symptom of the condition. To keep genital herpes from returning, famciclovir is usually taken twice a day for up to 1 year. When famciclovir is used to treat herpes infection in people infected with HIV, it is usually taken twice a day for 7 days. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take famciclovir exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor. Use this medication as soon as possible after symptoms appear.

Continue to take famciclovir even if you feel well. Do not stop taking famciclovir without talking to your doctor.

Before taking Famvir

• tell your doctor and pharmacist if you are allergic to famciclovir, penciclovir cream (Denavir), acyclovir (Zovirax), any other medications, or lactose.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplement, and herbal products you are taking or plan to take, especially probenecid (Benemid).
• tell your doctor if you have or have ever had problems with your immune system, human immunodeficiency virus infection (HIV), or acquired immunodeficiency syndrome (AIDS); galactose intolerance or glucose-galactose malabsorption (inherited conditions where the body is not able to tolerate lactose); or kidney or liver disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking famciclovir, call your doctor.
• you should know that famciclovir may make you drowsy, dizzy, confused, or disoriented. Do not drive a car or operate machinery until you know how this medication affects you.