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ANTIINFECTIVES FOR SYSTEMIC USE › ANTIVIRALS FOR SYSTEMIC USE › DIRECT ACTING ANTIVIRALS › Nucleosides and nucleotides excl. reverse transcriptase inhibitors
famciclovir
J05AB09
Forms & Strengths
- Oral tablets: 125 mg
- Oral tablets: 250 mg
- Oral tablets: 500 mg
Adult Dosing
- Herpes zoster (shingles): 500 mg orally every 8 hours for 7 days
- Genital herpes (initial episode): 250 mg orally every 8 hours for 7-10 days
- Genital herpes (recurrent episodes): 125 mg orally twice daily for 5 days or 1000 mg twice daily for 1 day
- Genital herpes suppression: 250 mg orally twice daily
- Labial herpes (cold sores): 1500 mg as a single dose
- Renal impairment adjustment required: CrCl < 60 mL/min requires dose reduction or extended interval
Pediatric Dosing
- Safety and efficacy in pediatric patients (< 18 years) have not been established
Indications
- Treatment of acute herpes zoster (shingles)
- Treatment and suppression of recurrent genital herpes
- Treatment of initial episode of genital herpes
- Treatment of recurrent episodes of herpes labialis (cold sores) in immunocompetent hosts
Mechanism of Action
- Prodrug of penciclovir; rapidly converted in the intestinal wall and liver to penciclovir
- Penciclovir is phosphorylated by viral thymidine kinase in HSV-1, HSV-2, and VZV-infected cells
- Penciclovir triphosphate competitively inhibits viral DNA polymerase and halts viral DNA chain elongation
Contraindications
- Hypersensitivity to famciclovir, penciclovir, or any component of the formulation
Adverse Reactions
- Headache
- Nausea
- Diarrhea
- Fatigue
- Dizziness
- Abdominal pain
- Rare: Acute renal failure, hallucinations, urticaria, Stevens-Johnson syndrome
Drug Interactions
- Probenecid: May increase plasma concentrations of penciclovir by decreasing renal tubular secretion
- Digoxin: Minor increases in digoxin exposure possible; monitor clinically
- No clinically significant pharmacokinetic drug interactions reported with antacids or other cytochrome P450 inhibitors/inducers
Curated Content: Needs Vetting Before Put to Clinical Use