famciclovir famciclovir famciclovir 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). famciclovirclinical datapronunciation/ˌfæmˈsaɪkloʊˌvɪər/ trade namesfamvirahfs/drugs.commonographmedlineplusa694038pregnancycategory au: b1 routes ofadministrationoralatc codej05ab09 (who) s01ad07 (who)legal statuslegal status au: s3 (pharmacist only) uk: pom (prescription only) us: ℞-only pharmacokinetic databioavailability75–77%protein binding20–25%metabolismhepatic, circulation, intestinal wall (to penciclovir)elimination half-life2–2.3 hoursexcretionrenal, faecalidentifiers iupac name 2--4-(2-amino-9h-purin-9-yl)butyl acetate cas number104227-87-4 ypubchem cid3324drugbankdb00426 ychemspider3207 yuniiqic03ani02keggd00317 ychebichebi:4974 ychemblchembl880 ycomptox dashboard (epa)dtxsid0023038 echa infocard100.158.713 chemical and physical dataformulac14h19n5o4molar mass321.337 g·mol−13d model (jsmol)interactive imagemelting point103 °c (217 °f) smiles o=c(occ(coc(=o)c)ccn1c2nc(ncc2nc1)n)c inchi inchi=1s/c14h19n5o4/c1-9(20)22-6-11(7-23-10(2)21)3-4-19-8-17-12-5-16-14(15)18-13(12)19/h5,8,11h,3-4,6-7h2,1-2h3,(h2,15,16,18) ykey:ggxkwvwzwmljeh-uhfffaoysa-n y (verify) famciclovir was patented in 1983 and approved for medical use in 1994. in 2007, the united states food and drug administration approved the first generic version of famciclovir. generic tablets are manufactured by teva pharmaceuticals and mylan pharmaceuticals. medical uses 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. adverse effects side effects: mild to extreme stomach upset, headaches, mild fever. herpes 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.