What the FDA labels say about taking them together
Famciclovir and penciclovir
Famciclovir's FDA label of September 17, 2025 names penciclovir in its contraindications section; the penciclovir label PlainMeds reads does not name famciclovir. The famciclovir label: “DRUG INTERACTIONS Probenecid: May increase penciclovir levels. Monitor for evidence of penciclovir toxicity”
Check it at the source: the famciclovir FDA label on DailyMed (effective September 17, 2025, Macleods Pharmaceuticals Limited); the penciclovir FDA label on DailyMed (effective September 4, 2019, Mylan Pharmaceuticals Inc.).
What does the famciclovir label say about penciclovir?
Famciclovir label, contraindicationsCONTRAINDICATIONS Famciclovir tablets are contraindicated in patients with known hypersensitivity to the product, its components, or Denavir ® (penciclovir cream).
Famciclovir label, drug interactionsDRUG INTERACTIONS Probenecid: May increase penciclovir levels. Monitor for evidence of penciclovir toxicity
Source: FDA drug label (Famciclovir), Macleods Pharmaceuticals Limited, effective September 17, 2025 (SPL set eeeee9c4-8566-4100-8ca4-3df936a3365d), via openFDA; the full label on DailyMed
What does the penciclovir label say about famciclovir?
Penciclovir's label (effective September 4, 2019) does not name famciclovir in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Penciclovir), Mylan Pharmaceuticals Inc., effective September 4, 2019 (SPL set 9cb88c28-d9c9-45e3-b4fe-083327f122de), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Famciclovir | Penciclovir | |
|---|---|---|
| Labeled for | Herpes and shingles | Herpes and shingles |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.214 per tablet 125 mg tablet | $52.15 per gram 1% cream |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once