Famciclovir
FAMVIR
Pronunciation: fam-SYE-kloe-veer (FAM-veer)
What it isOral penciclovir prodrug inhibiting viral DNA polymerase; herpes zoster and genital herpes.
Why this oneTurns 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.
Famciclovir prescription history
Animated chart of estimated U.S. prescriptions per year, Antivirals (non-HIV) (1966–2026). Famciclovir enters in 1994 (estimated).
FDA-approved for
- herpes/shingles (1994)
Principal riskReduce the dose in renal impairment
Classes and tags
Clinical profile
Legacy pregnancy categoryUnknown / historical label unavailable
Defining liabilityAgent-specific renal, hepatic, hematologic, metabolic and drug-interaction toxicity.
FDA label
Read the full label on DailyMed ↗
NO BOXED WARNINGS
| 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)
Available strengths
- tab 125, 250, 500 mg
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
Cost
Generic entry2007
Active metabolites
Open Famciclovir in the interactive console ↗
Self-check
- Which active drug does famciclovir deliver orally?
Penciclovir. - Does famciclovir eradicate latent herpes infection?
No.