What the FDA labels say about taking them together
Felbamate and valproic acid
Valproic acid's FDA label of January 24, 2025 names felbamate in its drug interactions section; felbamate's label does not name valproic acid itself but warns about its class (Anti-seizure medicines). The valproic acid label: “DRUG INTERACTIONS Hepatic enzyme-inducing drugs can increase valproate clearance, while enzyme inhibitors (e.g., felbamate) can decrease valproate clearance.”
Check it at the source: the felbamate FDA label on DailyMed (effective August 15, 2025, Viatris Specialty LLC); the valproic acid FDA label on DailyMed (effective January 24, 2025, PAI Holdings, LLC dba PAI Pharma).
What does the felbamate label say about valproic acid?
Felbamate's label does not name valproic acid itself; it warns about its class (Anti-seizure medicines):
Felbamate label, drug interactionsCBZ epoxide ↓ ↑ ↓ Phenobarbital ↑ ↓ Specific Effects of Felbatol® on Other Antiepileptic Drugs Phenytoin Felbatol ® causes an increase in steady-state phenytoin plasma concentrations.
Felbamate label, drug interactionsEffects of Other Antiepileptic Drugs on Felbatol ® Phenytoin Phenytoin causes an approximate doubling of the clearance of Felbatol ® (felbamate) at steady-state and, therefore, the addition of phenytoin causes an approximate 45% decrease in the steady-state trough concentrations of Felbatol ® as compared to the same dose of Felbatol ® given as monotherapy.
Source: FDA drug label (Felbatol), NDA020189 (Mylan Speciality Lp), as published by Viatris Specialty LLC, effective August 15, 2025 (SPL set 2f522701-397a-11de-8a39-0800200c9a66), via openFDA; the full label on DailyMed
What does the valproic acid label say about felbamate?
Valproic acid label, drug interactionsDRUG INTERACTIONS Hepatic enzyme-inducing drugs (e.g., phenytoin, carbamazepine, phenobarbital, primidone, rifampin) can increase valproate clearance, while enzyme inhibitors (e.g., felbamate) can decrease valproate clearance.
Source: FDA drug label (VALPROIC ACID), PAI Holdings, LLC dba PAI Pharma, effective January 24, 2025 (SPL set 7d5cb52e-37dd-4dfa-a6f4-09f9548846c6), 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
| Felbamate | Valproic acid | |
|---|---|---|
| Labeled for | Seizures and epilepsy | Seizures and epilepsy, Migraine |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $1.00 per tablet 600 mg tablet | $0.243 per capsule 250 mg capsule |
| Shortage now | No current entry | Listed; available |
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