What is Famtrex?
Famtrex is an antiviral medicine that is used to treat infections caused by herpes viruses, including genital herpes, cold sores, and shingles.
Famtrex is sometimes used in people with human immunodeficiency virus (HIV) who develop herpes outbreaks around the mouth, genitals, or anal area.
Famtrex 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.
Before taking this medicine
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.
How should I take famciclovir?
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.
What happens if I miss a dose?
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.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
What should I avoid while taking famciclovir?
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.
Famciclovir side effects
Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
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 may include:
- headache; or
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.
Usual Adult Dose for Herpes Simplex — Mucocutaneous/Immunocompetent Host:
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
Famtrex 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)
Famtrex 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 Famtrex therapy beyond 1 year have not been established.
Usual Adult Dose for Herpes Zoster:
500 mg orally every 8 hours for 7 days
Famtrex 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
Famtrex is most effective if started at the earliest sign or symptom of a cold sore (such as tingling, burning, itching, pain, or lesion).
Detailed Famtrex dosage information
What other drugs will affect Famtrex?
Other drugs may affect Famtrex, 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.
Famciclovir drug interactions (more detail)