Famciclovir belongs to the family of medications known as antivirals. It is used to treat genital herpes and shingles (a painful rash caused by some herpes viruses). It prevents the virus from making DNA (genetic material) and copying itself, and so leads to lower levels of virus in the blood.

Your doctor may have suggested this medication for conditions other than the ones listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

Shingles: The recommended adult dose of famciclovir is 500 mg three times daily for 7 days. Start treatment within 72 hours of the onset of the rash.

Genital herpes: The recommended adult dose of famciclovir is 125 mg twice a day for 5 days. Start treatment during the prodromal period (the period during which early symptoms warn of a herpes flare-up) or as soon as you notice lesions.

To prevent recurrent episodes, the recommended dose is 250 mg twice a day for up to 1 year.

The tablets should be swallowed whole and may be taken with or without food.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is very important that this medication be taken on a regular schedule as prescribed by the doctor. Take this medication for the full duration of the prescription even if you feel better. If you miss a dose of this medication, take it as soon as you remember it. If it is almost time for your next dose, skip the missed dose and carry on with your regular schedule. Do not take a double dose to make up for a missed one.

125 mg
Each white, round, biconvex, film-coated tablet, with bevelled edges, debossed with "FAMVIR" on one side and "125" on the other, contains famciclovir 125 mg. Nonmedicinal ingredients: hydroxypropyl cellulose, hydroxypropyl methylcellulose, lactose, magnesium stearate, polyethylene glycols, sodium starch glycolate and titanium dioxide.

250 mg
Each white, round, biconvex, film-coated tablet, with bevelled edges, debossed with "FAMVIR" on one side and "250" on the other, contains famciclovir 250 mg. Nonmedicinal ingredients: hydroxypropyl cellulose, hydroxypropyl methylcellulose, lactose, magnesium stearate, polyethylene glycols, sodium starch glycolate and titanium dioxide.

500 mg
Each white, oval, biconvex, film-coated tablet, with bevelled edges, debossed with "FAMVIR" on one side and "500" on the other, contains famciclovir 500 mg. Nonmedicinal ingredients: hydroxypropyl cellulose, hydroxypropyl methylcellulose, lactose, magnesium stearate, polyethylene glycols, sodium starch glycolate and titanium dioxide.

Anyone allergic to famciclovir or to any of the ingredients of the medication should not use it.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

More common:

• headache

Less common:
• diarrhea
• dizziness
• nausea
• unusual tiredness or weakness
• vomiting

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Transmission: Genital herpes is a sexually transmitted infection with an increased risk of passing it on to a sexual partner during acute episodes. It is not known if famciclovir will prevent transmission of the infection. People using the medication for this reason are advised to avoid intercourse when lesions or symptoms are present (even if treatment with an antiviral has been started) in order to avoid infecting partners. Genital herpes can also be transmitted in the absence of symptoms.

Pregnancy: The safety of famciclovir during pregnancy has not been established. It should not be used during pregnancy unless the potential benefits outweigh the risks.

Breast-feeding: It is not known whether this medication passes into breast milk. A decision should be made whether to stop nursing or to stop taking the medication, taking into account the importance of famciclovir to the mother.

Children: The safety and effectiveness of this medication for children and adolescents under the age of 18 years have not been established.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.