What the FDA labels say about taking them together
Phenytoin and rufinamide
Rufinamide's FDA label of December 15, 2022 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name rufinamide. The rufinamide label: “AED Co-administered: Phenytoin; Influence of Rufinamide on AED concentration a): Increase by 7 to 21% b); Influence of AED on Rufinamide concentration: Decrease by 25 to 46% c) ’ d) Independent of dose or concentration …”
Check it at the source: the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.); the rufinamide FDA label on DailyMed (effective December 15, 2022, Eisai Inc.).
What does the phenytoin label say about rufinamide?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name rufinamide 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
What does the rufinamide label say about phenytoin?
Rufinamide label, drug interactionsAED Co-administered: Phenytoin; Influence of Rufinamide on AED concentration a): Increase by 7 to 21% b); Influence of AED on Rufinamide concentration: Decrease by 25 to 46% c) ’ d) Independent of dose or concentration of phenytoin
Source: FDA drug label (Banzel), Eisai Inc., effective December 15, 2022 (SPL set 0a3fa925-1abd-458a-bd57-4ae780a1ef2d), 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
| Phenytoin | Rufinamide | |
|---|---|---|
| Labeled for | Seizures and epilepsy | n/a |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.145 per capsule 100 mg capsule | $0.203 per mL 40 mg/mL suspension |
| 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