|
This information has been developed and provided by an independent third-party source. Merck & Co., Inc. does not endorse and is not responsible for the accuracy of the content, or for practices or
standards of non-Merck sources.
Pronunciation
(fam SYE kloe veer)
Generic Available (U.S.)
Yes
Brand Names: U.S.
Brand Names: Canada
Pharmacologic Category
Use: Labeled Indications
Treatment of acute herpes zoster (shingles); treatment and suppression of recurrent episodes of genital herpes in immunocompetent patients; treatment of herpes labialis (cold sores) in immunocompetent patients; treatment of recurrent mucocutaneous/genital herpes simplex in HIV-infected patients
Use: Dental
Management of acute herpes zoster (shingles); treatment of recurrent herpes labialis in immunocompetent patients
Pregnancy Risk Factor
B
Pregnancy Considerations
Teratogenic effects were not observed in animal studies. There are no adequate and well-controlled studies in pregnant women. Use only if benefit outweighs risk. A registry has been established for women exposed to famciclovir during pregnancy (888-669-6682).
Lactation
Excretion in breast milk unknown/not recommended
Breast-Feeding Considerations
There is no specific data describing the excretion of famciclovir in breast milk. Breast-feeding is not recommended by the manufacturer unless the potential benefits outweigh any possible risk. If herpes lesions are on breast, breast-feeding should be avoided in order to avoid transmission to infant.
Contraindications
Hypersensitivity to famciclovir, penciclovir, or any component of the formulation
Warnings/Precautions
Disease-related concerns:
• Renal impairment: Use with caution in patients with renal impairment; dosage adjustment required.
Dosage form specific issues:
• Lactose: Tablets contain lactose; do not use with galactose intolerance, severe lactase deficiency, or glucose-galactose malabsorption syndromes.
Other warnings/precautions:
• Appropriate use: Has not been established for use in initial episodes of genital herpes, patients with ophthalmic or disseminated zoster, or in immunocompromised patients with herpes zoster.
Adverse Reactions
Note: Frequencies vary with dose and duration. Single-dose treatment (herpes labialis) was associated only with headache (10%), diarrhea (2%), fatigue (1%), and dysmenorrhea (1%).
>10%:
Central nervous system: Headache (14% to 39%)
Gastrointestinal: Nausea (3% to 13%)
1% to 10%:
Central nervous system: Fatigue (1% to 5%), migraine (1% to 3%)
Dermatologic: Pruritus (≤4%), rash (≤3%)
Endocrine & metabolic: Dysmenorrhea (≤8%)
Gastrointestinal: Diarrhea (5% to 9%), abdominal pain (≤8%), flatulence (1% to 5%), vomiting (1% to 5%)
Hematologic: Neutropenia (3%)
Hepatic: Transaminases increased (2% to 3%), bilirubin increased (2%)
Neuromuscular & skeletal: Paresthesia (≤3%)
<1%, postmarketing, and/or case reports: Anemia, cholestatic jaundice, confusion, delirium, disorientation, dizziness, erythema multiforme, hallucinations, somnolence, Stevens-Johnson syndrome, thrombocytopenia, toxic epidermal necrolysis, urticaria
Metabolism/Transport Effects
None known.
Drug Interactions
Zoster Vaccine: Famciclovir may diminish the therapeutic effect of Zoster Vaccine. Management: When possible, discontinue antiviral agents with anti-zoster activity (i.e., acyclovir, valacyclovir, famciclovir) for at least 24 hours prior to and 14 days after receiving a live attenuated zoster vaccine. Risk X: Avoid combination
Ethanol/Nutrition/Herb Interactions
Food: Rate of absorption and/or conversion to penciclovir and peak concentration are reduced with food, but bioavailability is not affected.
Storage
Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).
Mechanism of Action
Famciclovir undergoes rapid biotransformation to the active compound, penciclovir (prodrug), which is phosphorylated by viral thymidine kinase in HSV-1, HSV-2, and VZV-infected cells to a monophosphate form; this is then converted to penciclovir triphosphate and competes with deoxyguanosine triphosphate to inhibit HSV-2 polymerase, therefore, herpes viral DNA synthesis/replication is selectively inhibited.
Pharmacodynamics/Kinetics
Absorption: Food decreases maximum peak penciclovir concentration and delays time to penciclovir peak; AUC remains the same
Distribution: Vd: Penciclovir: 0.91-1.25 L/kg
Protein binding: Penciclovir: ≤20%
Metabolism: Famciclovir is rapidly deacetylated and oxidized to penciclovir (active prodrug); not via CYP
Bioavailability: Penciclovir: 69% to 85%
Half-life elimination: Penciclovir: 2-4 hours; Prolonged in renal impairment: Clcr 20-39 mL/minute: 5-8 hours, Clcr <20 mL/minute: 3-24 hours
Time to peak: Penciclovir: 0.9 hours; Cmax and Tmax are decreased and prolonged with noncompensated hepatic impairment
Excretion: Urine (73% primarily as penciclovir); feces (27%)
Dosage
Adults: Oral:
Acute herpes zoster: 500 mg every 8 hours for 7 days (Note: Initiate therapy within 72 hours of rash onset.)
Genital herpes simplex virus (HSV) infection in immunocompetent patients:
Initial episode: 250 mg 3 times/day for 7-10 days (CDC, 2010)
Recurrence: 1000 mg twice daily for 1 day (Note: Initiate therapy within 6 hours of symptoms/lesions)
Alternatively, the following regimens are also recommended: 125 mg twice daily for 5 days or 500 mg as a single dose, followed by 250 mg twice daily for 2 days (CDC, 2010)
Suppressive therapy: 250 mg twice daily for up to 1 year; Note: Duration not established, but efficacy/safety have been demonstrated for 1 year (CDC, 2010)
Recurrent herpes labialis (cold sores): 1500 mg as a single dose; initiate therapy at first sign or symptom such as tingling, burning, or itching (initiated within 1 hour in clinical studies)
Recurrent mucocutaneous/genital HSV infection in HIV patients: 500 mg twice daily for 7 days or 5-10 days (CDC, 2010)
Prevention of HSV reactivation in HIV patients: 500 mg twice daily (CDC, 2010)
Dosing interval in renal impairment:
Herpes zoster:
Clcr 40-59 mL/minute: Administer 500 mg every 12 hours
Clcr 20-39 mL/minute: Administer 500 mg every 24 hours
Clcr <20 mL/minute: Administer 250 mg every 24 hours
Hemodialysis: Administer 250 mg after each dialysis session.
Recurrent genital herpes: Treatment (single day regimen):
Clcr 40-59 mL/minute: Administer 500 mg every 12 hours for 1 day
Clcr 20-39 mL/minute: Administer 500 mg as a single dose
Clcr <20 mL/minute: Administer 250 mg as a single dose
Hemodialysis: Administer 250 mg as a single dose after dialysis session.
Recurrent genital herpes: Suppression:
Clcr 20-39 mL/minute: Administer 125 mg every 12 hours
Clcr <20 mL/minute: Administer 125 mg every 24 hours
Hemodialysis: Administer 125 mg after each dialysis session.
Recurrent herpes labialis: Treatment (single dose regimen):
Clcr 40-59 mL/minute: Administer 750 mg as a single dose
Clcr 20-39 mL/minute: Administer 500 mg as a single dose
Clcr <20 mL/minute: Administer 250 mg as a single dose
Hemodialysis: Administer 250 mg as a single dose after dialysis session.
Recurrent orolabial or genital herpes in HIV-infected patients:
Clcr 20-39 mL/minute: Administer 500 mg every 24 hours
Clcr <20 mL/minute: Administer 250 mg every 24 hours
Hemodialysis: Administer 250 mg after each dialysis session.
Administration: Oral
May be administered without regard to meals.
Monitoring Parameters
Periodic CBC during long-term therapy
Dietary Considerations
May be taken without regard to meals.
Patient Education
This is not a cure for genital herpes. May cause mild GI disturbances (eg, nausea, vomiting, constipation, diarrhea), fatigue, headache, or muscle aches and pains. If these are severe, contact prescriber.
Geriatric Considerations
For herpes zoster (shingles) infections, famciclovir should be started within 72 hours of the appearance of the rash to be effective. Famciclovir has been shown to accelerate healing, reduce the duration of viral shedding, and resolve posthepatic neuralgia faster than placebo. Adjust dose for estimated renal function.
Additional Information
Most effective for herpes zoster if therapy is initiated within 48 hours of initial lesion. Resistance may occur by alteration of thymidine kinase, resulting in loss of or reduced penciclovir phosphorylation (cross-resistance occurs between acyclovir and famciclovir). When treatment for herpes labialis is initiated within 1 hour of symptom onset, healing time is reduced by ~2 days.
Dental Health: Effects on Dental Treatment
No significant effects or complications reported
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
May cause sedation
Mental Health: Effects on Psychiatric Treatment
None reported
Nursing: Physical Assessment/Monitoring
Assess periodic CBC during long-term therapy. Monitor for persistent fatigue and gastrointestinal upset.
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, oral: 125 mg, 250 mg, 500 mg
Famvir®: 125 mg [contains lactose 26.9 mg/tablet]
Famvir®: 250 mg [contains lactose 53.7 mg/tablet]
Famvir®: 500 mg [contains lactose 107.4 mg/tablet]
Pricing: U.S. (www.drugstore.com)
Tablets (Famciclovir)
125 mg (30): $159.99
250 mg (30): $169.99
500 mg (30): $326.00
Tablets (Famvir)
125 mg (30): $201.00
250 mg (30): $216.99
500 mg (30): $450.01
References
Alrabiah FA and Sacks SL, “New Antiherpesvirus Agents. Their Targets and Therapeutic Potential,” Drugs, 1996, 52(1):17-32.
Boike SC, Pue MA, and Freed MI, “Pharmacokinetics of Famciclovir in Subjects With Varying Degrees of Renal Impairment,” Clin Pharmacol Ther, 1994, 55(4):418-26.
Boyd MR, Safrin S, and Kern ER, “Penciclovir: A Review of Its Spectrum of Activity, Selectivity, and Cross Resistance Pattern,” Antivir Chem Chemother, 1993, 4:3-11.
Centers for Disease Control and Prevention (CDC), "Sexually Transmitted Diseases Treatment Guidelines, 2010," MMWR Recomm Rep, 2010, 59(RR-12):1-110.
Daniels S and Schentag JJ, “Drug Interaction Studies and Safety of Famciclovir in Healthy Volunteers: A Review,” Antivir Chem Chemother, 1993, 4:57-64.
De Clercq E, “Antivirals for the Treatment of Herpesvirus Infections,” J Antimicrob Chemother, 1993, 32(Suppl A):121-32.
Gill KS and Wood MJ, “The Clinical Pharmacokinetics of Famciclovir,” Clin Pharmacokinet, 1996, 31(1):1-8.
Goffin E, Horsmans Y, Pirson Y, et al, “Acute Necrotico-Hemorrhagic Pancreatitis After Famciclovir Prescription,” Transplantation, 1995, 59(8):1218-9.
Hodge RA, “Famciclovir and Penciclovir: The Mode of Action of Famciclovir Including Its Conversion to Penciclovir,” Antivir Chem Chemother, 1993, 4:67-84.
Luber AD and Flaherty JF Jr, “Famciclovir for Treatment of Herpesvirus Infections,” Ann Pharmacother, 1996, 30(9):978-85.
Perry CM and Wagstaff AJ, “Famciclovir. A Review of Its Pharmacological Properties and Therapeutic Efficacy in Herpesvirus Infections,” Drugs, 1995, 50(2):396-415.
Pue MA and Benet LZ, “Pharmacokinetics of Famciclovir in Man,” Antivir Chem Chemother, 1993, 4(Suppl 1):47-55.
Sacks SL, “Genital Herpes Simplex Virus and Its Treatment Focus on Famciclovir,” Semin Dermatol, 1996, 15(2 Suppl 1):32-6.
Spruance SL, Bodsworth N, Resnick H, et al, “Single-Dose, Patient-Initiated Famciclovir: A Randomized, Double-Blind, Placebo-Controlled Trial for Episodic Treatment of Herpes Labialis,” J Am Acad Dermatol, 2006, 55(1):47-53.
Tyring SK, Barbarash RA, Nahlik JE, et al, “Famciclovir for the Treatment of Acute Herpes Zoster: Effects on Acute Disease and Postherpetic Neuralgia,” Ann Intern Med, 1995, 123(2):89-96.
Tyring SK, “Efficacy of Famciclovir in the Treatment of Herpes Zoster,” Semin Dermatol, 1996, 15(2 Suppl 1):27-31.
International Brand Names
Lexi-Comp.com
Last full review/revision January 2012
Content last modified January 2012
| 
