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 mucus 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.
This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.
Before taking famciclovir,
- 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.
Unless your doctor tells you otherwise, continue your normal diet.
Take the missed dose as soon as you remember it, and take any remaining doses for that day at evenly spaced intervals. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
Famciclovir may cause side effects. Tell your doctor if any of these symptoms or those listed in the SPECIAL PRECAUTIONS section above are severe or do not go away:
- diarrhea or loose stools
- stomach pain
- painful menstrual periods
If you experience any of the following side effects, call your doctor immediately:
- pain, burning, numbness, or tingling in the hands or feet
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at Web Site] or by phone [1-800-332-1088].
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). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.
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.
AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Last Reviewed: September 1, 2010.