What the FDA labels say about taking them together
Oxcarbazepine and phenytoin
Oxcarbazepine's FDA label of December 16, 2025 names phenytoin in its drug interactions section, and phenytoin's label names oxcarbazepine too. The oxcarbazepine label: “DRUG INTERACTIONS Phenytoin: Increased phenytoin levels.”
Check it at the source: the oxcarbazepine FDA label on DailyMed (effective December 16, 2025, Novartis Pharmaceuticals Corporation); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the oxcarbazepine label say about phenytoin?
Oxcarbazepine label, drug interactionsDRUG INTERACTIONS Phenytoin: Increased phenytoin levels.
Oxcarbazepine label, warnings and precautionsIn the 14 controlled epilepsy studies, 2.5% of TRILEPTAL-treated patients (38/1524) had a sodium of less than 125 mmol/L at some point during treatment, compared to no such patients assigned placebo or active control (carbamazepine and phenobarbital for adjunctive and monotherapy substitution studies, and phenytoin and valproate for the monotherapy initiation studies).
Oxtellar Xr label (Supernus Pharmaceuticals, Inc., October 22, 2025), drug interactionsDRUG INTERACTIONS Phenytoin, Carbamazepine, and Phenobarbital: Coadministration decreased blood levels of an active metabolite of Oxtellar XR:
Source: FDA drug label (Oxtellar Xr, NDA202810), Supernus Pharmaceuticals, Inc., effective October 22, 2025 (SPL set aa610e56-1d1d-11e1-8bc2-0800200c9a66), via openFDA
Source: FDA drug label (Trileptal), Novartis Pharmaceuticals Corporation, effective December 16, 2025 (SPL set 4c5c86c8-ab7f-4fcf-bc1b-5a0b1fd0691b), via openFDA; the full label on DailyMed
What does the phenytoin label say about oxcarbazepine?
Phenytoin label, drug interactionsInteracting Agent: Antiepileptic drugs; Examples: Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate
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
| Oxcarbazepine | Phenytoin | |
|---|---|---|
| Labeled for | Seizures and epilepsy | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.167 per tablet 300 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