What the FDA labels say about taking them together
Armodafinil and phenytoin
Armodafinil's FDA label of September 2, 2025 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name armodafinil. The armodafinil label: “Effects of NUVIGIL on CYP2C19 Substrates Elimination of drugs that are substrates for CYP2C19 may be prolonged by NUVIGIL via inhibition of metabolic enzymes, with resultant higher systemic exposure.”
Check it at the source: the armodafinil FDA label on DailyMed (effective September 2, 2025, Golden State Medical Supply, Inc.); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the armodafinil label say about phenytoin?
Armodafinil label, drug interactionsEffects of NUVIGIL on CYP2C19 Substrates Elimination of drugs that are substrates for CYP2C19 (e.g., phenytoin, diazepam, propranolol, omeprazole, and clomipramine) may be prolonged by NUVIGIL via inhibition of metabolic enzymes, with resultant higher systemic exposure.
Source: FDA drug label (Nuvigil), NDA021875 (Nuvo Pharms), as published by Golden State Medical Supply, Inc., effective September 2, 2025 (SPL set 3dd49302-f757-d945-e063-6294a90afcba), via openFDA; the full label on DailyMed
What does the phenytoin label say about armodafinil?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name armodafinil 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
| Armodafinil | Phenytoin | |
|---|---|---|
| Labeled for | n/a | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.788 per tablet 150 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