What is Famciclovir: Uses, Warnings & Interactions

Updated May 14, 2025  •  Published Dec 30, 2020

Famciclovir overview

BRAND NAMES:

  • Famvir

Generic Names:

  • Famciclovir

Uses:

  • Treats herpes virus infections, including shingles, cold sores, and genital herpes. This medicine will not cure herpes, but may prevent a breakout of herpes sores or blisters.

Therapeutic Classes:

  • Antiviral

Forms:

  • Tablet

How it’s taken:

  • By mouth

What is Famciclovir used for?

What form(s) does Famciclovir come in

  • Tablet

What are common Famciclovir doses?

  • Tablet 125MG

  • Tablet 250MG

  • Tablet 500MG

Common Famciclovir prescriptions

  • Famciclovir
    125mg tablet

  • Famciclovir
    250mg tablet

  • Famciclovir
    500mg tablet

How to take Famciclovir

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

  • Your doctor will tell you how much medicine to use. Do not use more than directed.

  • 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.

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

  • 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.

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

  • Your doctor will tell you how much medicine to use. Do not use more than directed.

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

What to do if you miss a dose of Famciclovir

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

  • Oral routeAsk your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.

  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Famciclovir contraindications

  • This medicine is not right for everyone. Do not use it if you had an allergic reaction to famciclovir or penciclovir cream.

Famciclovir warnings

  • Tell your doctor if you are pregnant or breastfeeding, or if you have kidney disease, liver disease, or lactose absorption problems.

  • This medicine may make you dizzy or drowsy. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

  • 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.

  • Call your doctor if your symptoms do not improve or if they get worse.

  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Famciclovir interactions

  • Some medicines can affect how famciclovir works. Tell your doctor if you are using probenecid.

  • 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.

  • Call your doctor if your symptoms do not improve or if they get worse.

Famciclovir side effects

Serious 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

  • Blistering, peeling, red skin rash

  • Decrease in how much or how often you urinate

  • Rapid weight gain, swelling of your face, ankles, or hands

  • Tiredness.

Less Serious Side Effects

  • Confusion, dizziness, sleepiness

  • Headache

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