Famciclovir

Famciclovir (INN) is a guanosine 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.

Indications
Famciclovir is indicated for the treatment of herpes zoster (shingles), treatment of herpes simplex virus 2 (genital herpes), herpes labialis (cold sores) in immunocompetent patients and for the suppression of recurring episodes of herpes simplex virus 2. It is also indicated for treatment of recurrent episodes of herpes simplex in HIV patients.

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.

Adverse effects
Side effects: mild to extreme stomach upset, headaches, mild fever.

Early Treatment
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. Use of famciclovir in this manner has been shown to reduce the amount of latent virus in the neural ganglia compared to no treatment or treatment with valaciclovir. 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. Neither drug affected latency if treatment was delayed for several months. 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.

Suppression
Famvir (famciclovir) vs Valtrex (valaciclovir) clinical trials done in 1997 found that long-term treatment with valaciclovir was more effective than famciclovir at suppressing latent viral shedding of Herpes, but the research was not released for 10 years by the funder, the owner of Famvir.