Famciclovir (famciclovir)

Famciclovir is metabolized mainly in the liver to the active drug penciclovir. In patients with well-compensated chronic liver disease such as chronic hepatitis, chronic alcohol abuse, or primary biliary cirrhosis, bioavailability of penciclovir was not affected. Therefore, modification of famciclovir dosage is not necessary in patients with well-compensated liver disease. The manufacturer does not make specific recommendations for patients with uncompensated hepatic impairment, since the pharmacokinetics of famciclovir has not been evaluated in these patients.

Famciclovir is eliminated mainly by the kidneys via tubular secretion and glomerular filtration. In patients with moderately or severely impaired renal function, the frequency of administration of famciclovir should be decreased in response to the degree of impairment as indicated by creatinine clearance.

Because penciclovir (the active metabolite) is readily removed from plasma during hemodialysis, famciclovir should be administered after each hemodialysis session when the drug is used for the treatment of herpes zoster, treatment of recurrent mucocutaneous HSV infections in HIV-infected patients, or suppression of recurrent genital herpes. Famciclovir is administered once as a single dose after a hemodialysis session when the drug is used for the treatment of recurrent genital herpes or treatment of recurrent herpes labialis. The manufacturer recommends that a famciclovir dose (250 mg for patients with herpes zoster, 250 mg for HIV-infected patients with recurrent mucosal or cutaneous HSV infection, or 125 mg for patients receiving the drug for suppression of recurrent genital herpes) be administered following each hemodialysis session. The manufacturer recommends that a famciclovir dose (250 mg for patients with recurrent genital herpes, 250 mg for patients with recurrent herpes labialis) be administered once as a single dose after a hemodialysis session.

Famciclovir is administered orally without regard to meals. Food does not affect the systemic bioavailability or elimination of famciclovir.

No dosing information is available for this tab.

No dosing information is available for this tab.

Famciclovir not metabolized by CYP isoenzymes.

There are no contraindication interactions for this drug.

There are no severe interactions for this drug.

There are no moderate interactions for this drug.

There is no enhanced messaging for this drug.

There are no contraindication contraindications for this drug.

There are no severe contraindications for this drug.

There are no moderate contraindications for this drug.

There is no enhanced messaging for this drug.

There are no severe adverse reactions for this drug.

There are no less severe adverse reactions for this drug.

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No enhanced messaging available.

Reproduction studies using oral famciclovir dosages up to 1 g/kg daily in rats and rabbits (approximately 3.6-21.6 and 1.8-10.8 times the human systemic exposure to penciclovir, respectively, based on AUC comparisons) and IV dosages of 360 mg/kg daily in rats (2-12 times the human dose based on body surface area comparisons) or 120 mg/kg daily in rabbits (1.5-9 times the human dose based on body surface area comparisons) have not revealed evidence of adverse effects on embryofetal development. Similar studies using IV penciclovir dosages up to 80 mg/kg daily in rats (0.4-2.6 times the human dose based on body surface area comparisons) or 60 mg/kg daily in rabbits (0.7-4.2 times the human dose based on body surface area comparisons) also did not reveal evidence of adverse effects on embryofetal development. There are no adequate and well-controlled studies to date using famciclovir in pregnant women, and the drug should be used during pregnancy only when clearly needed.

To monitor maternal-fetal outcome of pregnant women exposed to famciclovir, the manufacturer maintains a Famciclovir Pregnancy Registry. The registry may be contacted by calling 888-669-6682.

Reproduction studies using famciclovir or penciclovir in rats, mice, and dogs revealed evidence of testicular toxicity following repeated oral administration of high dosages. Testicular changes, including atrophy of the seminiferous tubules, reduction in sperm count, and/or increased incidence of sperm with abnormal morphology or reduced motility, were observed. The degree of toxicity was related to dose and duration of exposure. In male rats, decreased fertility was observed following 10 weeks of dosing at 500 mg/kg daily (1.9-11.4 times the human AUC). Administration of famciclovir to male rats in dosages of 50 mg/kg daily (0.2-1.2 times the human systemic exposure based on AUC comparisons) for 26 weeks did not reveal evidence of sperm or testicular toxicity. Testicular toxicity was observed following administration of dosages of 600 mg/kg daily (0.4-2.4 times the human systemic exposure based on AUC comparisons) for 104 weeks in male mice and dosages of 150 mg/kg daily (1.7-10.2 times the human system exposure based on AUC comparisons) for 26 weeks in male dogs. No effect on spermatogenesis was observed in human males with genital herpes following oral famciclovir dosages of 250 mg twice daily for 18 weeks.

It is not known whether famciclovir or penciclovir is distributed into milk in humans. Following oral administration of famciclovir to lactating rats, penciclovir was distributed into breast milk at concentrations higher than those observed in plasma. Data on safety of famciclovir in infants currently is not available.

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