Drug Reference

Famciclovir

Nucleosides and nucleotides excl. reverse transcriptase inhibitors

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Therapeutic class
Nucleosides and nucleotides excl. reverse transcriptase inhibitors
Action class
Herpes Simplex Virus Nucleoside Analog DNA Polymerase Inhibitor
Mechanism
DNA Polymerase Inhibitors
Chemical class
Nucleoside Analog
Habit forming
No
Availability
Prescription (Rx)

Available as

750 MG · Oral Tablet500 MG · Oral Tablet125 MG · Oral Tablet250 MG · Oral Tablet

FDA label sections are from openFDA and may not reflect the most recent labeling — confirm against the current DailyMed label.

Uses
1 INDICATIONS & USAGE Famciclovir tablet, a prodrug of penciclovir, is a deoxynucleoside analog DNA polymerase inhibitor indicated for: Immunocompetent Adult Patients ( 1.1 ) • Herpes labialis (cold sores) o Treatment of recurrent episodes • Genital herpes o Treatment of recurrent episodes o Suppressive therapy of recurrent episodes • Herpes zoster (shingles) Human Immunodeficiency Virus (HIV)-Infected Adult Patients ( 1.2 ) • Treatment of recurrent episodes of orolabial or genital herpes Limitation of Use The efficacy and safety of famciclovir tablets have not been established for: • Patients with first episode of genital herpes • Patients with ophthalmic zoster • Immunocompromised patients other than for the treatment of recurrent episodes of orolabial or genital herpes in HIV-infected patients • Black and African American patients with recurrent genital herpes 1.1 Immunocompetent Adult Patients Herpes labialis (cold sores): Famciclovir tablets are indicated for the treatment of recurrent herpes labialis in adult patients. Genital herpes: Recurrent episodes: Famciclovir tablets are indicated for the treatment of recurrent episodes of genital herpes. The efficacy of famciclovir tablets when initiated more than 6 hours after onset of symptoms or lesions has not been established. Suppressive therapy: Famciclovir tablets are indicated for chronic suppressive therapy of recurrent episodes of genital herpes in adult patients. The efficacy and safety of famciclovir tablets for the suppression of recurrent genital herpes beyond 1 year have not been established. Herpes zoster (shingles): Famciclovir tablets are indicated for the treatment of herpes zoster in adult patients. The efficacy of famciclovir tablets when initiated more than 72 hours after onset of rash has not been established. 1.2 HIV-Infected Adult Patients Recurrent orolabial or genital herpes : Famciclovir tablets are indicated for the treatment of recurrent episodes of orolabial or genital herpes in HIV-infected adults. The efficacy of famciclovir tablets when initiated more than 48 hours after onset of symptoms or lesions has not been established. Limitation of Use The efficacy and safety of famciclovir tablets have not been established for: • Patients with first episode of genital herpes • Patients with ophthalmic zoster • Immunocompromised patients other than for the treatment of recurrent orolabial or genital herpes in HIV-infected patients • Black and African American patients with recurrent genital herpes
How it works
12.1 Mechanism of Action Famciclovir is an orally administered prodrug of the anti-alpha herpes viral agent penciclovir [see Microbiology ( 12.4 )].
How to use / dosing
2 DOSAGE & ADMINISTRATION Famciclovir tablets may be taken with or without food. Immunocompetent Adult Patients ( 2.1 ) Herpes labialis (cold sores) 1500 mg as a single dose Genital herpes Treatment of recurrent episodes Suppressive therapy Herpes Zoster (shingles) 1000 mg twice daily for 1 day 250 mg twice daily 500 mg every 8 hours for 7 days HIV-Infected Adult Patients ( 2.2 ) Recurrent episodes of orolabial or genital herpes 500 mg twice daily for 7 days Patients with renal impairment: Adjust dose based on creatinine clearance. ( 2.3 ) 2.1 Dosing Recommendation in Immunocompetent Adult Patients Herpes labialis (cold sores): The recommended dosage of famciclovir tablets for the treatment of recurrent herpes labialis is 1500 mg as a single dose. Therapy should be initiated at the first sign or symptom of herpes labialis (e.g., tingling, itching, burning, pain, or lesion). Genital herpes: Recurrent episodes: The recommended dosage of famciclovir tablets for the treatment of recurrent episodes of genital herpes is 1000 mg twice daily for 1 day. Therapy should be initiated at the first sign or symptom of a recurrent episode (e.g., tingling, itching, burning, pain, or lesion). Suppressive therapy: The recommended dosage of famciclovir tablets for chronic suppressive therapy of recurrent episodes of genital herpes is 250 mg twice daily. Herpes zoster (shingles): The recommended dosage of famciclovir tablets for the treatment of herpes zoster is 500 mg every 8 hours for 7 days. Therapy should be initiated as soon as herpes zoster is diagnosed. 2.2 Dosing Recommendation in HIV-Infected Adult Patients Recurrent orolabial or genital herpes: The recommended dosage of famciclovir tablets for the treatment of recurrent orolabial or genital herpes in HIV-infected patients is 500 mg twice daily for 7 days. Therapy should be initiated at the first sign or symptom of a recurrent episode (e.g., tingling, itching, burning, pain, or lesion). 2.3 Dosing Recommendation in Patients with Renal Impairment Dosage recommendations for adult patients with renal impairment are provided in Table 1 [see Use in Specific Populations ( 8.6 ), Clinical Pharmacology ( 12.3 )]. Table 1: Dosage Recommendations for Adult Patients with Renal Impairment Indication and Normal Dosage Regimen Creatinine Clearance (mL/min) Adjusted Dosage Regimen Dose (mg) Dosing Interval Single-Day Dosing Regimens Recurrent Genital Herpes 1000 mg every 12 hours for1 day ≥60 1000 every 12 hours for 1 day 40-59 500 every 12 hours for 1 day 20-39 500 single dose <20 250 single dose HD* 250 single dose following dialysis Recurrent Herpes Labialis 1500 mg single dose ≥60 1500 single dose 40-59 750 single dose 20-39 500 single dose <20 250 single dose HD* 250 single dose following dialysis Multiple-Day Dosing Regimens Herpes Zoster 500 mg every 8 hours ≥60 500 every 8 hours 40-59 500 every 12 hours 20-39 500 every 24 hours <20 250 every 24 hours HD* 250 following each dialysis Suppression of Recurrent Genital Herpes 250 mg every 12 hours ≥40 250 every 12 hours 20-39 125 every 12 hours <20 125 every 24 hours HD* 125 following each dialysis Recurrent Orolabial or Genital Herpes in HIV-Infected Patients 500 mg every 12 hours ≥40 500 every 12 hours 20-39 500 every 24 hours <20 250 every 24 hours HD* 250 following each dialysis *Hemodialysis
Side effects
6 ADVERSE REACTIONS Acute renal failure is discussed in greater detail in other sections of the label [see Warnings and Precautions ( 5 )]. The most common adverse events reported in at least 1 indication by greater than 10% of adult patients treated with famciclovir are headache and nausea. The most common adverse events reported in at least 1 indication by greater than 10% of adult patients are headache and nausea. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Hetero Labs Limited at 1-866-495-1995 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience in Adult Patients Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice. Immunocompetent patients: The safety of famciclovir has been evaluated in active- and placebo-controlled clinical studies involving 816 famciclovir-treated patients with herpes zoster (famciclovir, 250 mg three times daily to 750 mg three times daily), 163 famciclovir-treated patients with recurrent genital herpes (Famciclovir, 1000 mg twice daily); 1,197 patients with recurrent genital herpes treated with famciclovir as suppressive therapy (125 mg once daily to 250 mg three times daily) of which 570 patients received famciclovir (open-labeled and/or double-blind) for at least 10 months; and 447 famciclovir-treated patients with herpes labialis (Famciclovir, 1500 mg once daily or 750 mg twice daily). Table 2 lists selected adverse events. Table 2: Selected Adverse Events (all grades and without regard to causality) Reported by Greater Than or Equal to 2% of Patients in Placebo-Controlled Famciclovir Trials* Incidence Events Herpes Zoster † Recurrent Genital Herpes ‡ Genital Herpes- Suppression § Herpes Labialis ‡ Famciclovir (n=273) % Placebo (n=146) % Famciclovir (n=163) % Placebo (n=166) % Famciclovir (n=458) % Placebo (n=63) % Famciclovir (n=447) % Placebo (n=254) % Nervous System Headache 22.7 17.8 13.5 5.4 39.3 42.9 8.5 6.7 Paresthesia 2.6 0.0 0.0 0.0 0.9 0.0 0.0 0.0 Migraine 0.7 0.7 0.6 0.6 3.1 0.0 0.2 0.0 Gastrointestinal Nausea 12.5 11.6 2.5 3.6 7.2 9.5 2.2 3.9 Diarrhea 7.7 4.8 4.9 1.2 9.0 9.5 1.6 0.8 Vomiting 4.8 3.4 1.2 0.6 3.1 1.6 0.7 0.0 Flatulence 1.5 0.7 0.6 0.0 4.8 1.6 0.2 0.0 Abdominal Pain 1.1 3.4 0.0 1.2 7.9 7.9 0.2 0.4 Body as a Whole Fatigue 4.4 3.4 0.6 0.0 4.8 3.2 1.6 0.4 Skin and Appendages Pruritus 3.7 2.7 0.0 0.6 2.2 0.0 0.0 0.0 Rash 0.4 0.7 0.0 0.0 3.3 1.6 0.0 0.0 Reproductive (Female) Dysmenorrhea 0.0 0.7 1.8 0.6 7.6 6.3 0.4 0.0 * Patients may have entered into more than one clinical trial. † 7 days of treatment ‡ 1 day of treatment § daily treatment Table 3 lists selected laboratory abnormalities in genital herpes suppression trials. Table 3: Selected Laboratory Abnormalities in Genital Herpes Suppression Studies * Parameter Famciclovir (n = 660) † % Placebo (n = 210) † % Anemia (<0.8 x NRL) 0.1 0.0 Leukopenia (<0.75 x NRL) 1.3 0.9 Neutropenia (<0.8 x NRL) 3.2 1.5 AST (SGOT) (>2 x NRH) 2.3 1.2 ALT (SGPT) (>2 x NRH) 3.2 1.5 Total Bilirubin (>1.5 x NRH) 1.9 1.2 Serum Creatinine (>1.5 x NRH) 0.2 0.3 Amylase (>1.5 x NRH) 1.5 1.9 Lipase (>1.5 x NRH) 4.9 4.7 * Percentage of patients with laboratory abnormalities that were increased or decreased from baseline and were outside of specified ranges. † n values represent the minimum number of patients assessed for each laboratory parameter. NRH = Normal Range High. NRL = Normal Range Low. HIV-infected patients : In HIV-infected patients, the most frequently reported adverse events for famciclovir (500 mg twice daily; n=150) and acyclovir (400 mg, 5x/day; n=143), respectively, were headache (17% vs. 15%), nausea (11% vs. 13%), diarrhea (7% vs. 11%), vomiting (5% vs. 4%), fatigue (4% vs. 2%), and abdominal pain (3% vs. 6%). 6.2 Postmarketing Experience The adverse events listed below have been report

Safety advice

Conservative summary derived from FDA labeling — defaults to “consult your doctor” unless the label is explicit. Not a substitute for your clinician’s advice.

PregnancyUnsafe
8.1 Pregnancy Risk Summary Available data from pharmacovigilance reports with famciclovir use in pregnant women have not identified a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes. There are risks to the fetus associated with untreated herpes simplex virus during pregnancy (see Clinical Considerations). After oral administration, famciclovir (prodrug) is converted to penciclovir (active drug). In animal reproduction studies with famciclovir, no evidence of adverse developmental outcomes was observed at systemic exposures of penciclovir (AUC) slightly higher than those at the maximum recommended human dose (MRHD) of famciclovir (see Data). The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. Clinical Considerations Disease-associated maternal and/or embryo-fetal risk The risk of neonatal herpes infection varies from 30% to 50% for genital herpes simplex virus (HSV) infections that occur in late pregnancy (third trimester), whereas in early pregnancy, infection carries a risk of about 1%. A primary herpes outbreak during the first trimester of pregnancy has been associated with neonatal chorioretinitis, microcephaly and, in rare cases, skin lesions. In very rare cases, transplacental transmission can occur resulting in congenital infection, including microcephaly, hepatosplenomegaly, intrauterine growth restriction and stillbirth. Co-infection with HSV increases the risk of perinatal HIV transmission in women who had a clinical diagnosis of genital herpes during pregnancy. Data Animal Data Famciclovir was administered orally to pregnant rats and rabbits (up to 1000 mg/kg/day) on gestation Day(s) 6 to 15, and to rats on gestation Day 15 to lactation/post-partum Day 25. No adverse effects on embryo-fetal (rats and rabbits) or pre/post-natal (rats) development were observed up to the highest dose tested. During organogenesis, systemic exposures of penciclovir (active metabolite) were 3.4 times (rats) and 1.6 times (rabbits) the human systemic exposure of penciclovir based on AUC at the MRHD.
BreastfeedingConsult your doctor
…on gestation Day(s) 6 to 15, and to rats on gestation Day 15 to lactation/post-partum Day 25.…
AlcoholNo information
No specific information in the FDA label.
DrivingNo information
No specific information in the FDA label.
KidneyCaution
…or genital herpes 500 mg twice daily for 7 days Patients with renal impairment: Adjust dose based on creatinine clearance.…
LiverNo information
No specific information in the FDA label.
Warnings & precautions
5 WARNINGS AND PRECAUTIONS Acute renal failure: May occur in patients with underlying renal disease who receive higher than recommended doses of famciclovir for their level of renal function. Reduce dosage in patients with renal impairment. ( 2.3 , 8.6 ) 5.1 Acute Renal Failure Cases of acute renal failure have been reported in patients with underlying renal disease who have received inappropriately high doses of famciclovir for their level of renal function. Dosage reduction is recommended when administering famciclovir to patients with renal impairment [see Dosage and Administration ( 2.3 ), Use in Specific Populations ( 8.6 )].
Contraindications
4 CONTRAINDICATIONS Famciclovir tablets are contraindicated in patients with known hypersensitivity to the product, its components, or Denavir ® (penciclovir cream). Known hypersensitivity to the product, its components, or Denavir ® (penciclovir cream). ( 4 )

Pediatric use

8.4 Pediatric Use The efficacy of famciclovir has not been established in pediatric patients. The pharmacokinetic profile and safety of famciclovir (experimental granules mixed with OraSweet ® or tablets) were studied in 3 open-label studies. Study 1 was a single-dose pharmacokinetic and safety study in infants 1 month to less than 1 year of age who had an active herpes simplex virus (HSV) infection or who were at risk for HSV infection. Eighteen subjects were enrolled and received a single dose of famciclovir experimental granules mixed with OraSweet based on the patient's body weight (doses ranged from 25 mg to 175 mg). These doses were selected to provide penciclovir systemic exposures similar to the penciclovir systemic exposures observed in adults after administration of 500 mg famciclovir. The efficacy and safety of famciclovir have not been established as suppressive therapy in infants following neonatal HSV infections. In addition, the efficacy cannot be extrapolated from adults to infants because there is no similar disease in adults. Therefore, famciclovir is not recommended in infants. Study 2 was an open-label, single-dose pharmacokinetic, multiple-dose safety study of famciclovir experimental granules mixed with OraSweet in children 1 to less than 12 years of age with clinically suspected HSV or varicella zoster virus (VZV) infection. Fifty-one subjects were enrolled in the pharmacokinetic part of the study and received a single body weight adjusted dose of famciclovir (doses ranged from 125 mg to 500 mg). These doses were selected to provide penciclovir systemic exposures similar to the penciclovir systemic exposures observed in adults after administration of 500 mg famciclovir. Based on the pharmacokinetic data observed with these doses in children, a new weight-based dosing algorithm was designed and used in the multiple-dose safety part of the study. Pharmacokinetic data were not obtained with the revised weight-based dosing algorithm. A total of 100 patients were enrolled in the multiple-dose safety part of the study; 47 subjects with active or latent HSV infection and 53 subjects with chickenpox. Patients with active or latent HSV infection received famciclovir twice a day for 7 days. The daily dose of famciclovir ranged from 150 mg to 500 mg twice daily depending on the patient’s body weight. Patients with chickenpox received famciclovir three times daily for 7 days. The daily dose of famciclovir ranged from 150 mg to 500 mg three times daily depending on the patient’s body weight. The clinical adverse events and laboratory test abnormalities observed in this study were similar to these seen in adults. The available data are insufficient to support the use of famciclovir for the treatment of children 1 to less than 12 years of age with chickenpox or infections due to HSV for the following reasons: Chickenpox: The efficacy of famciclovir for the treatment of chickenpox has not been established in either pediatric or adult patie

⚑ About half of pediatric medication use is off-label and not described in FDA labels — absence of pediatric information does not mean a medicine is unused or unsafe in children. Confirm with your clinician.

Interactions (label text — not an interaction checker)
7 DRUG INTERACTIONS Probenecid: May increase penciclovir levels. Monitor for evidence of penciclovir toxicity. (7.2) 7.1 Potential for Famciclovir to Affect Other Drugs The steady-state pharmacokinetics of digoxin were not altered by concomitant administration of multiple doses of famciclovir (500 mg three times daily). No clinically significant effect on the pharmacokinetics of zidovudine, its metabolite zidovudine glucuronide, or emtricitabine was observed following a single oral dose of 500 mg famciclovir coadministered with zidovudine or emtricitabine. An in vitro study using human liver microsomes suggests that famciclovir is not an inhibitor of CYP3A4enzymes. 7.2 Potential for Other Drugs to Affect Penciclovir No clinically significant alterations in penciclovir pharmacokinetics were observed following single-dose administration of 500 mg famciclovir after pretreatment with multiple doses of allopurinol, cimetidine, theophylline, zidovudine, promethazine, when given shortly after an antacid (magnesium and aluminum hydroxide), or concomitantly with emtricitabine. No clinically significant effect on penciclovir pharmacokinetics was observed following multiple-dose (three times daily) administration of famciclovir (500 mg) with multiple doses of digoxin. Concurrent use with probenecid or other drugs significantly eliminated by active renal tubular secretion may result in increased plasma concentrations of penciclovir. The conversion of 6-deoxy penciclovir to penciclovir is catalyzed by aldehyde oxidase. Interactions with other drugs metabolized by this enzyme and/or inhibiting this enzyme could potentially occur. Clinical interaction studies of famciclovir with cimetidine and promethazine, in vitro inhibitors of aldehyde oxidase, did not show relevant effects on the formation of penciclovir. Raloxifene, a potent aldehyde oxidase inhibitor in vitro, could decrease the formation of penciclovir. However, a clinical drug-drug interaction study to determine the magnitude of interaction between penciclovir and raloxifene has not been conducted.
Overdose
10 OVERDOSAGE Appropriate symptomatic and supportive therapy should be given. Penciclovir is removed by hemodialysis.
Current FDA labels (DailyMed)

4 marketed products on record (RxNorm)

Reference only — not clinical advice. Verify against current FDA labeling and consult a licensed provider. About half of pediatric drug use is off-label and is not reflected in FDA labels; absence of pediatric information does not mean a medicine is unused or unsafe in children.