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Famciclovir

Brand names: Famvir (brand discontinued)

Famciclovir is an antiviral that shortens outbreaks of shingles, cold sores, and genital herpes.

Brand namesFamvir (brand discontinued)
Type of medicineAntiviral
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It works best started at the first sign of an outbreak.

What it's used for

  • Shingles
  • Cold sores
  • Genital herpes (outbreaks and prevention)

How to take it

  • Take it with or without food. Start early.
  • Doses are lower with kidney disease.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Headache
  • Nausea
  • Diarrhea
Call your provider todayConfusion or seeing things (more likely in older adults or with kidney disease)
Call 911A blistering, peeling, or widespread red rash, especially with fever

Warnings

  • Shingles near the eye needs same-day care.

Other medicines, foods, and alcohol

  • Probenecid may raise its level.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Talk with your provider.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember. If it's almost time for the next dose, skip the missed one. Don't double up, and still finish the full course.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.