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 BRAND NAMES
 MECHANISM OF ACTION
Famciclovir is an oral antiviral agent. It is a prodrug form (6-deoxy analog) of the antiviral agent Penciclovir with improved oral bioavailability.
Famciclovir undergoes rapid biotransformation to the active metabolite, Penciclovir. Penciclovir is a selective substrate for HSV-1, HSV-2, and varicella-zoster virus thymidine kinase (TK).
Cellular kinases convert the monophosphate form of the drug to the triphosphate. Penciclovir triphosphate selectively inhibits viral DNA polymerase by competing with deoxyguanosine triphosphate. Phosphorylation of penciclovir to a monophosphate form depends on viral TK, which only occurs in virus-infected cells. Inhibition of DNA synthesis of virus-infected cells inhibits viral replication. DNA synthesis in cells not infected with the virus is unaltered.
- Treatment of acute herpes zoster (shingles) in immunocompetent adult patients
- Treatment or suppression of recurrent genital herpes in immunocompetent patients
- Treatment of Herpes labialis (cold sores) in immunocompetent adult patients
- Treatment of recurrent orolabial or genital herpes in HIV-infected patients.
- Immunocompetent Adult Patients:
- Herpes labialis (cold sores): 1500 mg as a single dose
- Genital herpes:
- Treatment of recurrent episodes: 1000 mg twice daily for 1 day
- Suppressive therapy: 250 mg twice daily
- HIV-Infected Adult Patients:
- Recurrent episodes of orolabial or genital herpes: 500 mg twice daily for 7 days
Known hypersensitivity to Famciclovir or to Penciclovir (Topical)
- Acute renal failure: May occur in patients with underlying renal disease who receive higher than recommended doses of famciclovir tablets for their level of renal function. Reduce dosage in patients with renal impairment
Probenecid: May increase penciclovir levels. Monitor for evidence of penciclovir toxicity.
 PREGNANCY AND LACTATION
- Pregnancy Category B (US)
- Nursing mothers: Famciclovir tablets should not be used in nursing mothers unless the potential benefits outweigh the potential risks associated with treatment
 SIDE EFFECTS
The most common adverse events reported in at least one indication by >10% of adult patients are headache and nausea.