Famciclovir
FAMVIR
What it isOral penciclovir prodrug inhibiting viral DNA polymerase; herpes zoster and genital herpes.
Why this oneIt turns penciclovir into a practical oral systemic therapy; penciclovir itself is confined to topical use.
What limits itRenal impairment requires adjustment. Treatment shortens episodes but never eradicates latent virus.
FDA-approved for
- herpes/shingles (1994)
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Herpes labialis (cold sores), immunocompetent | Adults | 1500 mg single dose | 1500 mg single dose | 1500 mg single dose |
| Recurrent genital herpes, immunocompetent | Adults | 1000 mg BID x1 day | 1000 mg BID x1 day | |
| Suppression of recurrent genital herpes, immunocompetent | Adults | 250 mg BID | 250 mg BID | |
| Herpes zoster (shingles), immunocompetent | Adults | 500 mg q8h x7 days | 500 mg q8h x7 days | |
| Recurrent orolabial or genital herpes, HIV-infected | Adults | 500 mg BID x7 days | 500 mg BID x7 days |
Renal Dose reduction required per creatinine clearance (indication-specific renal dosing table)
Hepatic Mild-moderate impairment: no adjustment needed; severe impairment not studied (conversion to active penciclovir may be impaired, possibly decreasing efficacy).
Instructions
- May be taken with or without food
- Initiate at first sign or symptom (tingling, itching, burning, pain, or lesion)
Cautions
- Acute renal failure reported with inappropriately high doses in patients with underlying renal disease — reduce dose in renal impairment
Adverse reactions
- Headache
- Nausea
- Diarrhea
Pregnancy Pharmacovigilance data have not identified a drug-associated risk of birth defects, miscarriage, or adverse outcomes
Lactation No human milk data; penciclovir present in rat milk
NO BOXED WARNINGS
Principal riskReduce the dose in renal impairment
Cost, est. cash$10–$500/month
Generic entry2007
Classes and tags
Clinical profile
Legacy pregnancy categoryUnknown / historical label unavailable
Defining liabilityAgent-specific renal, hepatic, hematologic, metabolic and drug-interaction toxicity.
Active metabolites
Mechanism of action: Famciclovir ballicule
