Famciclovir (By mouth)
Treats herpes virus infections, including shingles (herpes zoster), cold sores (herpes labialis), and genital herpes (herpes simplex). This medicine will not cure herpes, but may prevent a breakout of herpes sores or blisters.
There may be other brand names for this medicine.
When This Medicine Should Not Be Used
You should not use this medicine if you have had an allergic reaction to famciclovir or penciclovir (Denavir®), or if you have a severe lactose absorption problem.
How to Use This Medicine
- Your doctor will tell you how much of this medicine to use and how often. Do not use more medicine or use it more often than your doctor tells you to.
- You may take this medicine with or without food.
- Take this medicine at the first sign of a herpes breakout or as soon as possible. The medicine might not work as well if you start treatment too late.
If a dose is missed:
- If you miss a dose or forget to use your medicine, use it as soon as you can. If it is almost time for your next dose, wait until then to use the medicine and skip the missed dose. Do not use extra medicine to make up for a missed dose.
How to Store and Dispose of This Medicine
- Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
- Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
- Keep all medicine away from children and never share your medicine with anyone.
Drugs and Foods to Avoid
Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.
- Make sure your doctor knows if you are also using probenecid (Benemid®, Probalan®).
Warnings While Using This Medicine
- Make sure your doctor knows if you are pregnant or breastfeeding, or if you have kidney disease.
- This medicine may make you dizzy or drowsy. Avoid driving, using machines, or doing anything else that could be dangerous if you are not alert.
- Famciclovir will not stop the spread of herpes during sex. Avoid having sex while you have herpes sores.
- Even if you have no signs of a herpes infection, it is still possible to spread the virus to others during sex. Talk with your doctor about ways to keep from spreading the virus.
- If your symptoms do not improve or if they get worse, call your doctor.
Possible Side Effects While Using This Medicine
Call your doctor right away if you notice any of these side effects:
- Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
- Confusion, dizziness, or drowsiness.
- Numbness, tingling, or burning pain in your hands, arms, legs, or feet.
- Seeing or hearing things which are not really there.
- Unusual bleeding, bruising, or weakness.
- Yellowing of your skin or the whites of your eyes.
If you notice these less serious side effects, talk with your doctor:
- Nausea, vomiting, diarrhea, upset stomach, or stomach pain.
- Painful or irregular menstrual periods (in women).
- Skin rash or itching.
If you notice other side effects that you think are caused by this medicine, tell your doctor
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088
- Last Reviewed on 06/12/2013
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This page was last updated: September 18, 2013