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Famciclovir for viral infections


You can take famciclovir tablets either with or without food.

Space out your doses evenly over the day, and complete the full course of treatment.

The main side-effects of famciclovir are headache, and feeling sick (nausea). These are generally mild and not troublesome.

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About famciclovir

Type of medicine

An antiviral medicine

Used for

Viral infections in adults

Also called


Available as


Famciclovir is used to treat infections caused by two common viruses - herpes zoster and herpes simplex. The herpes zoster virus is the cause of shingles. Herpes simplex viruses cause genital herpes. You will have been prescribed famciclovir to treat either shingles, or genital herpes. Famciclovir works by preventing viruses from multiplying, and this reduces the severity of the infection.

Before taking famciclovir

Some medicines are not suitable for people with certain conditions, and sometimes a medicine can only be used if extra care is taken. For these reasons, before you start taking famciclovir it is important that your doctor knows:

  • If you are pregnant, trying for a baby, or breastfeeding.

  • If you have any problems with the way your liver works, or if you have any problems with the way your kidneys work.

  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

  • If you have ever had an allergic reaction to a medicine.

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How to take famciclovir

  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about famciclovir, and it will also provide you with a full list of the side-effects which you could experience from taking it.

  • Your dose will depend upon the type of infection you have, so take famciclovir exactly as your doctor tells you to. Typically, doses range from 250 mg to 750 mg, and doses are taken either one, two or three times daily. Your doctor or pharmacist will tell you what dose is right for you, and this information will also be printed on the label of the pack to remind you.

  • Space out your doses evenly during the day. You can take famciclovir tablets either with or without food.

  • Even if you feel your infection has cleared up, keep taking the tablets until the course is finished (unless your doctor tells you to stop sooner). This is to prevent the infection from coming back. A course of treatment usually lasts for around 5-10 days, although some people need to take famciclovir for only one day, and other people need a course lasting for several months. If you still feel unwell after finishing your course of treatment, go back to see your doctor.

  • If you forget to take a dose, take it as soon as you remember and then continue as before. Try to take the correct number of doses each day, but do not take two doses at the same time to make up for a missed dose.

Getting the most from your treatment

  • If you have been prescribed famciclovir for genital herpes, do not have sex while you have sores or blisters. Even after these have healed, there is still a small chance that you may pass on the virus when you have sex - using a condom reduces this risk.

  • If you are having an operation or any other medical treatment, tell the person carrying out the treatment that you are taking famciclovir.

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Can famciclovir cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the more common ones associated with famciclovir. The best place to find a full list of the side-effects which can be associated with your medicine, is from the manufacturer's printed information leaflet supplied with the medicine. Alternatively, you can find an example of a manufacturer's information leaflet in the reference section below. Speak with your doctor or pharmacist if any of the following continue or become troublesome.

Very common

famciclovir side-effects

(these affect more than 1 in 10 people)

What can I do if I experience this?


Drink plenty of water and ask your pharmacist to recommend a suitable painkiller. If the headaches continue, speak with your doctor


famciclovir side-effects

(these affect fewer than 1 in 10 people)

What can I do if I experience this?

Feeling sick (nausea) or being sick (vomiting), diarrhoea, stomach ache

Stick to simple foods - avoid fatty or spicy meals

Itchy rash

If this becomes troublesome, speak with your doctor

Feeling dizzy

Do not drive and do not use tools or machines while affected

If you experience any other symptoms which you think may be due to the medicine, speak with your doctor or pharmacist for further advice.

How to store famciclovir

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Important information about all medicines

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

If you buy any medicines, check with a pharmacist that they are suitable to take with your other medicines.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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