Famciclovir
Encyclopedia
Famciclovir (icon) is a guanine
analogue antiviral drug
used for the treatment of various herpesvirus infections, most commonly for herpes zoster
(shingles). It is a prodrug
form of penciclovir with improved oral bioavailability
. Famciclovir is marketed under the trade name Famvir (Novartis
).
On August 24, 2007, the United States
Food and Drug Administration
approved the first generic version of famciclovir. Generic Famciclovir Tablets (125 mg, 250 mg, 500 mg) are manufactured by TEVA Pharmaceuticals
and Mylan Pharmaceuticals.
It is also indicated for
, has been shown to reduce the amount of latent virus in the neural ganglia. A review of human subjects treated for five days with Famciclovir 250 mg three times daily during their first herpes episode found that only 4.2 percent experienced a recurrence within six months after the first outbreak, a fivefold decrease compared to the 19 percent recurrence in acyclovir-treated patients. Despite these promising results, early Famciclovir treatment for herpes in this or similar dosage regimes has yet to find mainstream adoption. As a result, some doctors and patients have opted for off-label use
. One suggested regime is Famciclovir at 10–20 mg/kg per day for 5–14 days, with treatment to commence as soon as possible after the first herpes infection (not the first symptoms or outbreak), and the most effective time for initiating treatment to be five days or less after the first herpes infection.
Guanine
Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine . In DNA, guanine is paired with cytosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with...
analogue antiviral drug
Antiviral drug
Antiviral drugs are a class of medication used specifically for treating viral infections. Like antibiotics for bacteria, specific antivirals are used for specific viruses...
used for the treatment of various herpesvirus infections, most commonly for herpes zoster
Herpes zoster
Herpes zoster , commonly known as shingles and also known as zona, is a viral disease characterized by a painful skin rash with blisters in a limited area on one side of the body, often in a stripe...
(shingles). It is a prodrug
Prodrug
A prodrug is a pharmacological substance administered in an inactive form. Once administered, the prodrug is metabolised in vivo into an active metabolite, a process termed bioactivation. The rationale behind the use of a prodrug is generally for absorption, distribution, metabolism, and...
form of penciclovir with improved oral bioavailability
Bioavailability
In pharmacology, bioavailability is a subcategory of absorption and is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered...
. Famciclovir is marketed under the trade name Famvir (Novartis
Novartis
Novartis International AG is a multinational pharmaceutical company based in Basel, Switzerland, ranking number three in sales among the world-wide industry...
).
On August 24, 2007, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
approved the first generic version of famciclovir. Generic Famciclovir Tablets (125 mg, 250 mg, 500 mg) are manufactured by TEVA Pharmaceuticals
Teva Pharmaceutical Industries
Teva Pharmaceutical Industries Ltd. , is an international pharmaceutical company headquartered in Petah Tikva, Israel. It specializes in generic and proprietary pharmaceuticals and active pharmaceutical ingredients...
and Mylan Pharmaceuticals.
Indications
Famciclovir is indicated for the treatment of herpes zoster (shingles). Treatment of herpes simplex virus 2 (genital herpes) and herpes labialis (cold sores) in (non-)immunodeficient patients. Suppression of recurring episodes of herpes simplex virus 2. Treatment of recurrent episodes of herpes simplex in HIV patients.It is also indicated for
Dosing
Famciclovir comes as an oral tablet in 125 mg, 250 mg, and 500 mg dosage forms. To treat herpes zoster, Famciclovir is taken 500 mg every 8 hours (three times a day) for 7 days. To treat genital herpes it is taken twice a day for 1 day. To treat herpes labialis (cold sores), famciclovir is given as a single 1500 mg oral dose. It is also sometimes given in one single large dose as opposed to several days of scheduled small doses. Among other side effects, Famciclovir may cause an upset stomach. Take famciclovir with food or milk.Herpes post-exposure prophylaxis use
Several studies in humans and mice provide evidence that early treatment with Famciclovir soon after the first infection with herpes can significantly lower the chance of future outbreaks of herpes. Use of Famciclovir in this manner, known as post-exposure prophylaxisPost-exposure prophylaxis
Post-exposure prophylaxis is any prophylactic treatment started immediately after exposure to a pathogen , in order to prevent infection by the pathogen and the development of disease.-Rabies:...
, has been shown to reduce the amount of latent virus in the neural ganglia. A review of human subjects treated for five days with Famciclovir 250 mg three times daily during their first herpes episode found that only 4.2 percent experienced a recurrence within six months after the first outbreak, a fivefold decrease compared to the 19 percent recurrence in acyclovir-treated patients. Despite these promising results, early Famciclovir treatment for herpes in this or similar dosage regimes has yet to find mainstream adoption. As a result, some doctors and patients have opted for off-label use
Off-label use
Off-label use is the practice of prescribing pharmaceuticals for an unapproved indication or in an unapproved age group, unapproved dose or unapproved form of administration...
. One suggested regime is Famciclovir at 10–20 mg/kg per day for 5–14 days, with treatment to commence as soon as possible after the first herpes infection (not the first symptoms or outbreak), and the most effective time for initiating treatment to be five days or less after the first herpes infection.