Sounds like 'fam-SYE-kloe-vir'

Famciclovir is used to treat infections caused by viruses. Find out how to take it safely and possible side effects. Famciclovir is also called Famvir Once.

Famciclovir is no longer available in Aotearoa New Zealand. This page will not longer be updated.
Talk to your healthcare provider about your treatment options.
Type of medicine Also called
  • Antiviral (to treat infections caused by viruses)

  • Famvir Once®

What is famciclovir?

Famciclovir is used to treat herpes labialis, which causes cold sores around the mouth, lips, nostrils or nose. It must be used as soon possible after the first symptoms of a cold sore appear such as tingling, itching, burning, redness or swelling. Famciclovir should not be used if a hard crust has already formed on the cold sore. It works by stopping the growth of the virus that causes the infection. It reduces the severity of the infection and stops it from spreading. It helps the infection heal faster. Famciclovir does not kill the virus. The virus that cause this infection continues to live in your body. Famciclovir is not subsidised in New Zealand. It can be bought from your pharmacy, without a prescription. Talk to your pharmacist to check if famciclovir is suitable for you. Famciclovir is available as tablets (500 milligrams).


  • The dose of famciclovir is 3 tablets taken together as one dose (= 1500 milligrams). 
  • Always take your famciclovir exactly as directed by your doctor your pharmacist. The pharmacy label on your medicine will tell you how much famciclovir to take, how often to take it and any special instructions.

How to take famciclovir

  • Swallow your famciclovir tablets with a glass of water.
  • Take 3 famciclovir tablets together in one dose. 
  • You can take famciclovir with or without food.
  • Drink plenty of water while taking famciclovir, to keep your kidneys working well (unless your doctor advises you otherwise). 

Precautions before taking famciclovir

  • Are you pregnant or breastfeeding?
  • Do you have liver or kidney problems?
  • Are you are taking or using any other medicines? This includes any medicines you buy without a prescription, such as herbal and complementary medicines.
  • Have you have ever had an allergic reaction to a medicine?

If so, it’s important that you tell your doctor before you start taking famciclovir. Sometimes a medicine isn’t suitable for a person with certain conditions or it can only be used with extra care.

What are the side effects of famciclovir?

Like all medicines, famciclovir can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Headache
  • Nausea (feeling sick)
  • Diarrhoea (runny poos)    
  • This may settle after a few hours.

  • Signs of an allergic reaction such as skin rash, itching, swelling of the lips, face, and mouth or difficulty breathing
  • Tell your doctor immediately or ring HealthLine 0800 611 116.
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product

Learn more

The following links have more information on famciclovir. Be aware that websites from other countries may contain information that differs from New Zealand recommendations.

Famciclovir NZ Formulary
Famciclovir (ApoHealth ONCE) Medsafe NZ Consumer Medicine Information

Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 19 Dec 2018