Famciclovir

What is Famiciclovir and how does it work?

Famciclovir is an antiviral medication that works by inhibiting DNA of viruses from replicating, so that the virus cannot multiply. It is used to treat the virus that causes cold sores, Herpes Simplex 1, or HSV-1, and the virus that usually causes genital herpes, HSV-2. HSV-1/HSV-2 first enters the body via the skin, mouth, or genitals, and migrates to the nerves. There, it can stay quiet, or “dormant” for a period of time before reactivating and causing symptoms. Symptoms of a genital herpes outbreak  include pain, burning, tingling and itching between 6 hours to 4 days before the actual sore appears. This period is called the “prodrome” and treatment is most effective when started as soon as possible. The available treatments for genital herpes are Acyclovir, Valacyclovir, and Famciclovir. The benefit of Famciclovir is it has a shorter treatment duration. 

How quickly does Famciclovir work?

Famciclovir works best when taken at the earliest sign of an outbreak. Although the medication will take effect immediately, you may not start to have relief until several hours or days after starting treatment. Treatment shortens the team to healing of the lesions and decreases the duration of viral shedding (contagious period).

Active ingredients

The active ingredient in Famciclovir is the antiviral drug famciclovir (500mg)

Inactive ingredients

Famciclovir contains the following inactive ingredients: hydroxypropyl cellulose, hydroxypropyl methylcellulose, lactose, magnesium stearate, polyethylene glycols, sodium starch glycolate and titanium dioxide.

The ingredients may vary by manufacturer; the ingredients listed above are the ingredients in Famvir.

Famiciclovir dosage

For the first episode of genital herpes, the treatment dosage is:

• Famciclovir 250mg three times a day for 7 to 10 days.

The dosage of Famciclovir to treat a recurrent episode of genital herpes (ie, you have had genital herpes in the past and this is a recurrence) is:

• 1000mg twice daily, for a single day
• OR 125mg twice daily for five days
• OR 500mg once, followed by 250mg twice daily for two days.

The treatment works best when started at the first symptom and within 72 hours (ie. tingling, itching, burning, pain or an eruption). 

The dosage of Famiciclovir to treat cold sores (herpes labialis) is 1,500mg (3 x 500mg tablets) as a single dose. Treatment works best when started at the first symptom (ie. tingling, itching, burning, pain or an eruption around the lips). 

How to take Famiciclovir

Take the dosage and treatment length prescribed. Famiciclovir does not have to be taken with food. 

Precautions

• If taken in excessively high doses in patients with underlying kidney disease, Famciclovir can cause kidney failure.

• Famciclovir is not a cure for herpes; you could still pass the virus onto others while being treated.

• Let your doctor know if you have kidney disease, as the dose may have to be reduced based on your kidney function.

• Let your doctor know if you have HIV or are immunocompromised.

Side effects

The most common side effects of Famiciclovir are headaches and nausea. A range of other side effects ahve been reported. It is important that you always read the patient information leaflet before taking any medication, including Famiciclovir. 

Drug interactions

There are very few drug interactions with Famciclovir. Some include: Cladribine, Talimogene Laherparepvec, Varicella virus vaccine, and Zoster vaccine (do not take this medication within 2 weeks of these vaccinations because it may make the vaccines less effective). 

Contraindications

Famciclovir is contraindicated if you have an allergy to it or any of its ingredients.  Famvir contains lactose; if you have a rare genetic problem of galactose intolerance or lactase deficiency, discuss this with your doctor.