Famciclovir

Oral
Herpes zoster (shingles)

Oral
Recurrent herpes labialis

Oral
Genital herpes

Oral
Acute treatment of recurrent mucocutaneous herpes in HIV-infected patients

Oral
Acute treatment of recurrent episodes of genital herpes

Oral
Suppression of recurrent episodes of genital herpes

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.

May be taken with or without food.

Hypersensitivity to famciclovir and penciclovir.

Renal impairment. Pregnancy and lactation.

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.

PO: B

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.

Monitor haematological function.

Acute renal failure in patients w/ renal disease. Management: Supportive and symptomatic treatment. May be removed by haemodialysis.

Reduced renal excretion resulting to increased plasma concentration w/ probenecid. Raloxifen may reduce the formation of penciclovir, the active metabolite of famciclovir.

Food may reduce the rate of absorption of famciclovir.

Description:
Mechanism of Action: 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.

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

Store at 20-25°C.

Antivirals

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.