What the FDA labels say about taking them together
Divalproex and phenobarbital
Divalproex's FDA label of March 31, 2026 names phenobarbital in its drug interactions section; phenobarbital's label does not name divalproex itself but warns about its class (Anti-seizure medicines). The divalproex 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 divalproex FDA label on DailyMed (effective March 31, 2026, AbbVie Inc.); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the divalproex label say about phenobarbital?
Divalproex 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 (Depakote), AbbVie Inc., effective March 31, 2026 (SPL set 08a65cf4-7749-4ceb-6895-8f4805e2b01f), via openFDA; the full label on DailyMed
What does the phenobarbital label say about divalproex?
Phenobarbital's label does not name divalproex 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
| Divalproex | Phenobarbital | |
|---|---|---|
| Labeled for | Bipolar disorder, Migraine, Seizures and epilepsy | Seizures and epilepsy |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.194 per tablet 500 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