What the FDA labels say about taking them together
Oxcarbazepine and phenobarbital
Oxcarbazepine's FDA label of December 16, 2025 names phenobarbital in its drug interactions section; phenobarbital's label does not name oxcarbazepine itself but warns about its class (Anti-seizure medicines). The oxcarbazepine label: “Reduced dose of phenytoin may be required Carbamazepine, Phenytoin, and Phenobarbital:”
Check it at the source: the oxcarbazepine FDA label on DailyMed (effective December 16, 2025, Novartis Pharmaceuticals Corporation); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the oxcarbazepine label say about phenobarbital?
Oxcarbazepine label, drug interactionsReduced dose of phenytoin may be required ( 7.1 ) Carbamazepine, Phenytoin, and Phenobarbital:
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 phenobarbital label say about oxcarbazepine?
Phenobarbital's label does not name oxcarbazepine itself; it warns about its class (Anti-seizure medicines):
Phenobarbital label, warnings and precautionsIf a rash occurs, the patient should be evaluated for signs and symptoms of Drug Reaction with Eosinophilia and Systemic Symptoms [see Warnings and Precautions (5.6)]. Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), also known as multiorgan hypersensitivity, has been reported in patients taking antiepileptic drugs, including phenobarbital.
Phenobarbital label, warnings and precautionsAntiepileptic drugs (AEDs) increase the risk of suicidal thoughts or behavior in adolescents and adults.
Source: FDA drug label (Phenobarbital), Chartwell RX, LLC, effective August 27, 2026 (SPL set 74428144-fb24-40a5-a670-3b876e2d116c), 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 | Phenobarbital | |
|---|---|---|
| Labeled for | Seizures and epilepsy | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.167 per tablet 300 mg tablet | $0.213 per tablet 100 mg tablet |
| Shortage now | No current entry | A presentation being discontinued |
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