famciclovir (Famvir)

Introduction

Tradename: Famvir.

Indications

• out-patient Herpes simplex virus (HSV) infection
  • Herpes simplex labialis
• treatment of acute Herpes zoster (shingles) or Herpes simplex type-2 (genital Herpes)
  • not responsive to acyclovir

Dosage

Herpes Zoster: 500 mg PO every 8 hours for 7 days

Tabs: 500 mg. Dose adjustment for renal failure:

Creatinine clearance	dose
> 60 mL/min	500 mg every 8 hours
40-59 mL/min	500 mg every 12 hours
10-39 mL/min	500 mg every 24 hours
> 10 mL/min	250 mg every 24 hours

Pharmacokinetics

• food decreased peak & the time to peak concentrations, but overall absorption is the same
• oral bioavailability is 77% (much better than acyclovir)
• rapidly deacylated & oxidized to penciclovir
• 1/2life of penciclovir is 2-3 hours (10-22 hours ESRD)
• > 90% of penciclovir is eliminated unchanged in the urine

elimination via kidney

Adverse effects

• common (> 10%)
  • headache, nausea
• less common (1-10%)
  • fatigue, fever, dizziness, somnolence, diarrhea, vomiting, constipation, anorexia, abdominal pain, rigors, paresthesia
• other
  • pruritus

Drug interactions

• cimetidine
• digoxin increased by 20%
• probenecid increases penciclovir concentration

• drug interaction(s) of antibiotics with warfarin

Mechanism of action

• undergoes rapid bio-transformation to penciclovir
• penciclovir is converted intracellularly by viral thymidine kinase to penciclovir triphosphate
• penciclovir triphosphate inhibits viral DNA synthesis

More general terms

• antiviral agent

Additional terms

• penciclovir (Denavir)

Database

• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=3324