Herpes simplex virus, mucocutaneous infection:
Genital:
Immunocompetent patients:
Treatment, initial episode (off-label use): Oral: 250 mg 3 times daily for 7 to 10 days; extend duration if lesion has not healed completely after 10 days (Ref).
Treatment, recurrent episode: Oral: 1 g twice daily for 1 day or 500 mg as a single dose, followed by 250 mg twice daily for 2 days or 125 mg twice daily for 5 days. Note: Treatment is most effective when initiated during the prodrome or within 1 day of lesion onset (Ref).
Suppressive therapy (eg, for severe and/or frequent recurrences): Oral: 250 mg twice daily. Note: Reassess need periodically (eg, annually) (Ref).
Immunocompromised patients (including patients with HIV):
Treatment, initial (off-label use) or recurrent episode: Oral: 500 mg twice daily for 5 to 10 days; extend treatment duration if lesions have not healed completely after 10 days (Ref). Note: Severe disease should be treated initially with IV acyclovir; may switch to famciclovir when lesions begin to regress and continue for at least 10 days total and until lesions have resolved completely (Ref).
Suppressive therapy (eg, for severe and/or frequent recurrences) (off-label use): Oral: 500 mg twice daily. Note: Reassess need periodically (eg, annually) (Ref).
Orolabial: Note: Initiate therapy at earliest symptom.
Immunocompetent patients:
Treatment, initial infection (eg, gingivostomatitis): Oral: 250 mg 3 times daily or 500 mg twice daily for 7 to 10 days (Ref).
Treatment, recurrent infection (eg, cold sores): Oral: 1.5 g as a single dose.
Immunocompromised patients (including patients with HIV):
Treatment, initial or recurrent infection: Oral: 500 mg twice daily for 5 to 10 days; extend treatment duration if lesions have not healed completely after 10 days (Ref).
Suppressive therapy (eg, for severe and/or frequent recurrences) (off-label use): Oral: 500 mg twice daily. Note: Reassess need periodically (eg, annually) (Ref).
Herpes simplex virus, prevention in solid organ transplant recipients (off-label use):
Herpes simplex virus–seropositive patients who do not require cytomegalovirus prophylaxis: Oral: 500 mg twice daily for at least 1 month post-transplant; may consider resumption of prophylaxis during periods of lymphodepletion associated with treatment of rejection (Ref).
Herpes zoster (shingles), treatment:
Note: Initiate at earliest sign or symptom. Antiviral treatment is most effective ≤72 hours after rash onset but may be initiated >72 hours in certain situations (eg, new lesions continue to appear); for immunocompromised patients, initiate treatment even if >72 hours after symptom onset unless all lesions have crusted (Ref).
Acute localized dermatomal lesion(s): Oral: 500 mg 3 times daily for 7 to 10 days; for slowly improving lesions, can extend therapy until resolution (Ref). For select immunocompromised patients at high risk of dissemination (eg, recent transplant, graft-versus-host disease), some experts suggest regimens used for disseminated zoster (Ref).
Disseminated zoster (extensive cutaneous lesions or visceral involvement): Oral: Initial therapy with acyclovir IV may be switched to famciclovir 500 mg 3 times daily to complete a 10- to 14-day course when formation of new lesions has ceased and signs/symptoms of visceral infection are improving (Ref).
Varicella infection (chickenpox) in patients with HIV (uncomplicated cases) (off-label use): Oral: 500 mg 3 times daily for 5 to 7 days (Ref).
Herpes zoster:
CrCl ≥60 mL/minute: No dosage adjustment necessary.
CrCl 40 to 59 mL/minute: Administer 500 mg every 12 hours
CrCl 20 to 39 mL/minute: Administer 500 mg every 24 hours
CrCl <20 mL/minute: Administer 250 mg every 24 hours
Hemodialysis: Administer 250 mg after each dialysis session.
Recurrent genital herpes: Treatment:
Single-day regimen:
CrCl ≥60 mL/minute: No dosage adjustment necessary.
CrCl 40 to 59 mL/minute: Administer 500 mg every 12 hours for 1 day
CrCl 20 to 39 mL/minute: Administer 500 mg as a single dose
CrCl <20 mL/minute: Administer 250 mg as a single dose
Hemodialysis: Administer 250 mg as a single dose after a dialysis session.
Alternatively the following recommendations have been made (Famvir Canadian product labeling):
CrCl >20 mL/minute/1.73 m2: Administer 125 mg every 12 hours
CrCl <20 mL/minute/1.73 m2: Administer 125 mg every 24 hours
Hemodialysis: Administer 125 mg after each dialysis session.
Recurrent genital herpes: Suppression:
CrCl ≥40 mL/minute: No dosage adjustment necessary.
CrCl 20 to 39 mL/minute: Administer 125 mg every 12 hours
CrCl <20 mL/minute: Administer 125 mg every 24 hours
Hemodialysis: Administer 125 mg after each dialysis session.
Recurrent herpes labialis: Treatment (single-dose regimen):
CrCl ≥60 mL/minute: No dosage adjustment necessary.
CrCl 40 to 59 mL/minute: Administer 750 mg as a single dose
CrCl 20 to 39 mL/minute: Administer 500 mg as a single dose
CrCl <20 mL/minute: Administer 250 mg as a single dose
Hemodialysis: Administer 250 mg as a single dose after a dialysis session.
Recurrent orolabial/genital (mucocutaneous) herpes in patients with HIV:
CrCl ≥40 mL/minute: No dosage adjustment necessary.
CrCl 20 to 39 mL/minute: Administer 500 mg every 24 hours
CrCl <20 mL/minute: Administer 250 mg every 24 hours
Hemodialysis: Administer 250 mg after each dialysis session.
Mild-to-moderate impairment: No dosage adjustment is necessary
Severe impairment: No dosage adjustment provided in manufacturer’s labeling; has not been studied. However, a 44% decrease in the Cmax of penciclovir (active metabolite) was noted in patients with mild-to-moderate impairment; impaired conversion of famciclovir to penciclovir may affect efficacy.
Refer to adult dosing.
(For additional information see "Famciclovir: Pediatric drug information")
Herpes simplex virus (HSV), genital infection: Limited data available:
Immunocompetent patients:
Initial episode, treatment: Children weighing ≥45 kg and Adolescents: Oral: 250 mg 3 times daily for 7 to 10 days; treatment duration can be extended if healing is incomplete after 10 days of therapy (Ref).
Recurrent episode, treatment: Children weighing ≥45 kg and Adolescents (Ref): Note: Initiate treatment within 1 day of lesion onset or during the prodrome that precedes some outbreaks.
One-day regimen: Oral: 1,000 mg twice daily for 1 day.
Two-day regimen: Oral: 500 mg once as a single dose, followed 12 hours later by 250 mg twice daily for 2 days.
Five-day regimen: Oral: 125 mg twice daily for 5 days.
Suppressive therapy: Children weighing ≥45 kg and Adolescents: Oral: 250 mg twice daily. Note: Reassess need periodically (eg, annually) (Ref).
Immunocompromised patients (including patients with HIV):
Initial or recurrent episodes, treatment: Adolescents: Oral: 500 mg twice daily for 5 to 10 days; extend treatment duration if lesions have not healed completely after 10 days. Consider treating initial episodes for at least 7 days (Ref).
Suppressive therapy: Adolescents: Oral: 500 mg twice daily. Note: Reassess need periodically (eg, annually) (Ref).
Herpes simplex virus, orolabial infection (cold sores): Limited data available:
Patients without HIV:
Recurrent episodes, treatment: Adolescents: Oral: 1,500 mg as a single dose (Ref).
Patients with HIV:
Initial or recurrent episodes, treatment: Adolescents: Oral: 500 mg twice daily for 5 to 10 days (Ref).
Suppressive therapy: Adolescents: Oral: 500 mg twice daily. Note: Reassess need periodically (eg, annually) (Ref).
Herpes zoster (shingles) in patients with HIV, treatment (Ref): Limited data available:
Acute localized dermatomal lesion: Adolescents: Oral: 500 mg 3 times daily for 7 to 10 days; for slowly improving lesions, can extend therapy until resolution.
Extensive cutaneous lesion or visceral involvement: Adolescents: Oral step-down therapy following initial parenteral acyclovir when formation of new lesions has ceased and signs and symptoms of visceral varicella zoster virus infection are improving: Oral: 500 mg 3 times daily to complete a 10- to 14-day course.
Varicella infection (chickenpox) in patients with HIV (uncomplicated cases), treatment: Limited data available: Adolescents: Oral: 500 mg 3 times daily for 5 to 7 days (Ref).
There are no pediatric-specific recommendations available; based on experience in adult patients; dosage adjustment suggested.
Mild to moderate impairment: There are no pediatric specific recommendations available; experience in adults suggests no dosage adjustment is necessary.
Severe impairment: There are no dosage adjustments provided in the manufacturer's labeling (has not been studied). A 44% decrease in the Cmax of penciclovir (active metabolite) was noted in adult patients with mild to moderate impairment; impaired conversion of famciclovir to penciclovir may affect efficacy.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Adverse reactions reported in adults.
>10%:
Gastrointestinal: Nausea (11% to 13%)
Nervous system: Headache (9% to 23%)
1% to 10%:
Dermatologic: Pruritus (2% to 4%), skin rash (3%)
Gastrointestinal: Abdominal pain (3%), diarrhea (2% to 8%), flatulence (≤5%), vomiting (≤5%)
Genitourinary: Dysmenorrhea (≤8%)
Hematologic & oncologic: Leukopenia (1%), neutropenia (3%)
Hepatic: Increased serum alanine aminotransferase (3%), increased serum aspartate aminotransferase (2%), increased serum bilirubin (2%)
Nervous system: Fatigue (≤5%), migraine (≤3%), paresthesia (≤3%)
<1%: Hematologic & oncologic: Anemia
Postmarketing:
Cardiovascular: Palpitations
Dermatologic: Erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, urticaria
Hematologic & oncologic: Thrombocytopenia
Hepatic: Abnormal hepatic function tests, cholestatic jaundice
Hypersensitivity: Anaphylactic shock, anaphylaxis, hypersensitivity angiitis (Chou 2012)
Nervous system: Confusion (Gales 1996), delirium, disorientation, dizziness, drowsiness, hallucination, seizure
Neuromuscular & skeletal: Bradykinesia (Gales 1996)
Hypersensitivity to famciclovir, penciclovir, or any component of the formulation
Disease-related concerns:
• Renal impairment: Use with caution in patients with renal impairment; dosage adjustment required. Acute renal failure has been reported with use of inappropriate high doses in patients with underlying renal disease.
Dosage form specific issues:
• Lactose: Tablets contain lactose; do not use with galactose intolerance, severe lactase deficiency, or glucose-galactose malabsorption syndromes.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral:
Generic: 125 mg, 250 mg, 500 mg
Yes
Tablets (Famciclovir Oral)
125 mg (per each): $5.81 - $6.39
250 mg (per each): $6.32 - $6.95
500 mg (per each): $12.69 - $13.95
Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral:
Famvir: 125 mg, 250 mg, 500 mg
Generic: 125 mg, 250 mg, 500 mg
Oral: May be administered without regard to meals.
Oral: May be administered without regard to meals
Treatment of acute herpes zoster (shingles) in immunocompetent patients; treatment and suppression of recurrent episodes of genital herpes in immunocompetent patients; treatment of herpes labialis (cold sores) in immunocompetent patients; treatment of recurrent orolabial/genital (mucocutaneous) herpes simplex in adult patients with HIV.
Herpes simplex virus, prevention in solid organ transplant recipients; Varicella infection (chickenpox) in patients with HIV
Famvir may be confused with Femara
Famciclovir may be confused with acyclovir
None known.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.
Cladribine: Agents that Undergo Intracellular Phosphorylation may diminish the therapeutic effect of Cladribine. Risk X: Avoid combination
Talimogene Laherparepvec: Antiherpetic Antivirals may diminish the therapeutic effect of Talimogene Laherparepvec. Risk C: Monitor therapy
Varicella Virus Vaccine: Famciclovir may diminish the therapeutic effect of Varicella Virus Vaccine. Management: When possible, avoid use of famciclovir within the 24 hours prior to administration of the varicella vaccine, and avoid use of famciclovir for 14 days after vaccination. Risk X: Avoid combination
Zoster Vaccine (Live/Attenuated): Famciclovir may diminish the therapeutic effect of Zoster Vaccine (Live/Attenuated). Risk X: Avoid combination
Rate of absorption and/or conversion to penciclovir and peak concentration are reduced with food, but bioavailability is not affected. Management: Administer without regard to meals.
Outcome information following maternal use of famciclovir during pregnancy is limited (Pasternak 2010; Wilton 1998). One study observed an increased risk of gastroschisis following use of antiherpetic medications such as famciclovir during the first trimester to treat maternal genital herpes; this risk was also increased in the offspring of women with genital herpes not receiving treatment (Ahrens 2013).
Famciclovir is approved for the treatment of genital herpes simplex virus (HSV). Primary HSV infection during the first trimester may be associated with neonatal chorioretinitis, microcephaly, and skin lesions. The risk of perinatal transmission is greater when the primary infection occurs during pregnancy. Maternal treatment decreases duration and severity of disease and duration of viral shedding. However, if treatment is needed during pregnancy, agents other than famciclovir are recommended (ACOG 2020; CDC [Workowski 2021]).
It is not known if famciclovir is present in breast milk.
According to the manufacturer, the decision to breastfeed during therapy should consider the risk of infant exposure, the benefits of breastfeeding to the infant, and benefits of treatment to the mother. Patients receiving treatment for herpetic lesions near or on the breast should not breastfeed (ACOG 2020). Patients with breast lesions can pump and discard milk to maintain milk supply until lesions are healed and breastfeeding can be resumed (D’Andrea 2019).
Periodic CBC during long-term therapy; renal function
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.
Absorption: Food decreases maximum peak penciclovir concentration and delays time to penciclovir peak; AUC remains the same
Distribution: Vd: Healthy adults: Penciclovir: 1.08 ± 0.17 L/kg
Protein binding: Penciclovir: <20%
Metabolism: Famciclovir is rapidly deacetylated and oxidized to penciclovir (active prodrug); in vitro data demonstrate that metabolism does not occur via CYP isoenzymes
Bioavailability: Penciclovir: 77% ± 8%
Half-life elimination:
Penciclovir: 2 to 4 hours; Prolonged in renal impairment:
CrCl 40 to 59 mL/minute: ~3.4 hours
CrCl 20 to 39 mL/minute: ~6.2 hours,
CrCl <20 mL/minute: ~13.4 hours
Intracellular penciclovir triphosphate: HSV 1: 10 hours; HSV 2: 20 hours; VZV: 7 hours
Time to peak: Penciclovir: ~1 hour
Excretion: Urine (73% primarily as penciclovir); feces (27%)
Altered kidney function: With CrCl 40 to 59 mL/minute, clearance is approximately 13 L/hour; CrCl 20 to 39 mL/minute, clearance is about approximately 4.2 L/hour; CrCl less than 20 mL/minute, clearance is approximately 1.6 L/hour.
Hepatic function impairment: Penciclovir Cmax decreased 44% and Tmax increased 0.75 hours in patients with hepatic impairment.
Older adult: Mean penciclovir AUC was 40% higher, and penciclovir renal clearance was 22% lower in elderly volunteers.
Sex: AUC of penciclovir was approximately 9.3 mcg•h/mL and 11.1 mcg•h/mL in male and female volunteers, respectively, after a single 500 mg dose. Penciclovir renal clearance was 28.5 L/h and 21.8 L/h, respectively.
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