Famciclovir


Concise Prescribing Info
Indications/Uses
Listed in Dosage.
Dosage/Direction for Use
Adult : PO Herpes zoster 500 mg tid for 7 days. Genital herpes 1st episode: 250 mg tid for 5 days. Recurrent genital herpes Acute treatment: 125 mg bid for 5 days or 1 g bid for 1 day. Suppression: 250 mg bid. Recurrent mucocutaneous herpes in HIV-infected patients 500 mg bid for 7 days. Recurrent herpes labialis 1.5 g as a single dose.
Dosage Details
Oral
Herpes zoster (shingles)
Adult: 500 mg tid for 7 days. Immunocompromised patients: 500 mg tid for 10 days.

Oral
Recurrent herpes labialis
Adult: 1.5 g as a single dose.

Oral
Genital herpes
Adult: 1st episode: 250 mg tid for 5 days. Immunocompromised patients: 500 mg bid for 7 days.

Oral
Acute treatment of recurrent mucocutaneous herpes in HIV-infected patients
Adult: 500 mg bid for 7 days.

Oral
Acute treatment of recurrent episodes of genital herpes
Adult: 125 mg bid for 5 days or 1 g bid for 1 day. Immunocompromised patients: 500 mg bid for 7 days.

Oral
Suppression of recurrent episodes of genital herpes
Adult: 250 mg bid. Immunocompromised patients: 500 mg bid. Suppressive treatment is interrupted every 6-12 mth for observation.
Renal Impairment
Oral:
Herpes zoster (shingles): Haemodialysis patients: 250 mg after each dialysis run during 7 days. Immunocompromised patients: Same dose but treatment is given for 10 days.
CrCl (mL/min) Dosage 
 <20 250 mg once daily for 7 days. 
 20-39 500 mg once daily for 7 days. 
 40-59 500 mg bid for 7 days. 
Genital herpes: Haemodialysis patients: 250 mg after each dialysis run during 5 days.
CrCl (mL/min) Dosage
 <20 250 mg once daily for 5 days.
 20-39 250 mg bid for 5 days. 
Acute treatment of recurrent episodes of genital herpes: Haemodialysis patients: 125 mg after each dialysis run during 5 days. Haemodialysis patients (immunocompromised): 250 mg after each dialysis run during 7 days.
CrCl (mL/min) Dosage
 <20 125 mg once daily for 5 days. 
 ≥20 125 mg bid for 5 days.
 <20 Immunocompromised: 250 mg once daily for 7 days. 
 20-39 Immunocompromised: 500 mg once daily for 7 days. 
Suppression of recurrent episodes of genital herpes: Haemodialysis patients: 125 mg after each dialysis run. Haemodialysis patients (immunocompromised): 250 mg after each dialysis run.
CrCl (mL/min) Dosage
 <20 125 mg once daily. Immunocompromised: 250 mg once daily. 
 20-39 125 mg bid. Immunocompromised: 500 mg once daily. 
Acute treatment of recurrent mucocutaneous herpes in HIV-infected patients: Haemodialysis patients: 250 mg after each dialysis run during 7 days.
CrCl (mL/min) Dosage 
 <20 250 mg once daily for 7 days.
 20-39 500 mg once daily for 7 days. 
Recurrent herpes labialis: Haemodialysis patients: 250 mg after dialysis run.
CrCl (mL/min)  Dosage 
 <20 250 mg as a single dose. 
 20-39 500 mg as a single dose. 
 40-59 750 mg as a single dose. 
Administration
May be taken with or without food.
Contraindications
Hypersensitivity to famciclovir and penciclovir.
Special Precautions
Renal impairment. Pregnancy and lactation.
Adverse Reactions
Headache, nausea, diarrhoea, fatigue, dizziness, fever, paraesthesia, somnolence, vomiting, constipation, anorexia, abdominal pain, flatulence, dyspepsia; increased serum levels of ALT, alkaline phosphatase, total bilirubin and albumin; pruritus, pharyngitis, sinusitis, injury, generalised pain, rigors, back pain, arthralgia; increased serum phosphate, Na and K levels; abnormal leukocyte counts, purpura, angioedema.
Potentially Fatal: Erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis.
Patient Counseling Information
This drug may cause dizziness, somnolence, confusion or other CNS disturbances, if affected, do not drive or operate machinery. Avoid sexual intercourse when symptoms of genital herpes are present.
MonitoringParameters
Monitor haematological function.
Overdosage
Acute renal failure in patients w/ renal disease. Management: Supportive and symptomatic treatment. May be removed by haemodialysis.
Drug Interactions
Reduced renal excretion resulting to increased plasma concentration w/ probenecid. Raloxifen may reduce the formation of penciclovir, the active metabolite of famciclovir.
Food Interaction
Food may reduce the rate of absorption of famciclovir.
Action
Description: Famciclovir rapidly undergoes biotransformation to penciclovir, which has inhibitory activity against HSV types 1 (HSV-1) and 2 (HSV-2), varicella-zoster virus (VZV). Thymidine kinase then phosphorylates penciclovir to a monophosphate form, which is then converted to penciclovir triphosphate. This inhibits HSV-2 DNA polymerase by competing w/ deoxyguanosine triphosphate, thus inhibiting herpes viral DNA synthesis and replication.
Pharmacokinetics:
Absorption: Rapidly absorbed from the GI tract. Food may delay absorption. Bioavailability: 77% (penciclovir). Time to peak plasma concentration: Approx 1 hr.
Distribution: Penciclovir: Volume of distribution: 0.91-1.25 L/kg. Plasma protein binding: <20%.
Metabolism: Converted to penciclovir via deacetylation and oxidation.
Excretion: Penciclovir: Via urine (73%); faeces (27%). Elimination half-life: 1.6-3 hr.
Chemical Structure

Chemical Structure Image
Famciclovir

Source: National Center for Biotechnology Information. PubChem Database. Famciclovir, CID=3324, https://pubchem.ncbi.nlm.nih.gov/compound/Famciclovir (accessed on Jan. 20, 2020)

Storage
Store at 20-25°C.
MIMS Class
References
Anon. Famciclovir. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. 18/06/2019. Accessed 30/10/2014.

Buckingham R (ed). Famciclovir. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 30/10/2014.

Famciclovir Tablet, Film Coated (Greenstone LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 30/10/2014.

Famvir Tablets. U.S. FDA. https://www.fda.gov/. Accessed 30/10/2014.

McEvoy GK, Snow EK, Miller J et al (eds). Famciclovir. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 30/10/2014.

Disclaimer: This information is independently developed by MIMS based on Famciclovir from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 MIMS. All rights reserved. Powered by MIMS.com
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