What the FDA labels say about taking them together
Erlotinib and phenytoin
Erlotinib's FDA label of June 10, 2024 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name erlotinib. The erlotinib label: “Increase the erlotinib dosage if co-administration with CYP3A4 inducers is unavoidable.”
Check it at the source: the erlotinib FDA label on DailyMed (effective June 10, 2024, Alembic Pharmaceuticals Limited); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the erlotinib label say about phenytoin?
Erlotinib label, drug interactionsIncrease the erlotinib dosage if co-administration with CYP3A4 inducers (e.g., carbamazepine, phenytoin, rifampin, rifabutin, rifapentine, phenobarbital and St. John's wort) is unavoidable [see Dosage and Administration (2.4)].
Source: FDA drug label (ERLOTINIB HYDROCHLORIDE), Alembic Pharmaceuticals Limited, effective June 10, 2024 (SPL set ab6f3cb3-34a8-4492-a5d7-fb6b055a2d6b), via openFDA; the full label on DailyMed
What does the phenytoin label say about erlotinib?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name erlotinib in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Phenytek), Mylan Pharmaceuticals Inc., effective October 15, 2024 (SPL set 0f94c791-8b07-4b41-927e-c9f28bec5f60), 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
| Erlotinib | Phenytoin | |
|---|---|---|
| Labeled for | Lung cancer | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $0.145 per capsule 100 mg capsule |
| 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