|Trade names||Famvir, others|
|Main uses||Herpes zoster (shingles), herpes simplex|
|Side effects||Headache, nausea, diarrhea|
|Metabolism||Liver, circulation, intestinal wall (to penciclovir)|
|Elimination half-life||2–2.3 hours|
|Chemical and physical data|
|Molar mass||321.337 g·mol−1|
|3D model (JSmol)|
|Melting point||103 °C (217 °F)|
Famciclovir, sold under the brand name Famvir among others, is an antiviral used to treat herpes zoster (shingles) and herpes simplex. It is used for genital herpes as well as cold sores and may be used to treat active outbreaks and to prevent outbreaks. It is taken by mouth.
Common side effects include headache, nausea, and diarrhea. Lower doses may be used in people with kidney problems. While there is no evidence of harm in pregnancy, such use has not been well studied. It is a prodrug of penciclovir. This results in a guanosine analogue which blocks viral DNA polymerase.
Famciclovir was patented in 1983 and approved for medical use in 1994. It is available as a generic medication. In the United Kingdom 14 tablets of 500 mg costs the NHS about £280 as of 2021. This amount in the United States is about 16 USD.
Famciclovir is indicated for the treatment of herpes zoster (shingles), treatment of herpes simplex virus 2 (genital herpes), herpes labialis (cold sores) in immunocompetent people 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.
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.
For herpes zoster it is used at a dose of 500 mg three times per day for 7 days.
Side effects: mild to extreme stomach upset, headaches, mild fever.
Society and culture
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