Penciclovir
from famciclovir
What it isThe active form of famciclovir, inhibiting viral DNA polymerase; herpes simplex and zoster.
Why it mattersA long intracellular half-life allows less frequent dosing than aciclovir.
What it changesIt requires viral thymidine kinase, so TK-mutant resistant virus escapes it entirely. Renally cleared.
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Recurrent herpes labialis (cold sores) on lips and face | Adults and adolescents ≥12 y | Apply topically q2h while awake × 4 days | Same | q2h waking hours, 4 days |
Renal Undefined
Hepatic Undefined
Instructions
- Start as early as possible (prodrome or first lesion appearance)
- Topical use on lips and face only; do not apply to mucous membranes; avoid in/near eyes (irritation)
Cautions
- For herpes labialis on lips/face only; application to mucous membranes not recommended; avoid eyes
- Evaluate lesions that fail to improve or worsen for secondary bacterial infection
- Effect not established in immunocompromised patients
Adverse reactions
- Application site reaction (1%)
- Hypesthesia/local anesthesia (<1%)
- Taste perversion (<1%)
- Erythematous rash (<1%)
- Postmarketing: headache, oral/pharyngeal edema, local edema, pruritus, urticaria
Pregnancy Not absorbed systemically after topical use; fetal exposure not expected
Lactation Not absorbed systemically by the mother; infant exposure not expected
NO BOXED WARNINGS
Principal riskTK-mutant virus escapes it entirely
Classes and tags
Clinical profile
Mechanism of action: Penciclovir ballicule
