What the FDA labels say about taking them together
Modafinil and phenytoin
Modafinil's FDA label of October 16, 2025 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name modafinil. The modafinil label: “Effects of PROVIGIL on CYP2C19 Substrates Elimination of drugs that are substrates for CYP2C19 may be prolonged by PROVIGIL via inhibition of metabolic enzymes, with resultant higher systemic exposure.”
Check it at the source: the modafinil FDA label on DailyMed (effective October 16, 2025, Golden State Medical Supply, Inc.); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the modafinil label say about phenytoin?
Modafinil label, drug interactionsEffects of PROVIGIL on CYP2C19 Substrates Elimination of drugs that are substrates for CYP2C19 (e.g., phenytoin, diazepam, propranolol, omeprazole, and clomipramine) may be prolonged by PROVIGIL via inhibition of metabolic enzymes, with resultant higher systemic exposure.
Source: FDA drug label (Provigil), NDA020717 (Nuvo Pharms), as published by Golden State Medical Supply, Inc., effective October 16, 2025 (SPL set 3b8d1c32-dac9-50e6-e063-6394a90aa5a5), via openFDA; the full label on DailyMed
What does the phenytoin label say about modafinil?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name modafinil 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
| Modafinil | Phenytoin | |
|---|---|---|
| Labeled for | n/a | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.344 per tablet 200 mg tablet | $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