What the FDA labels say about taking them together
Donepezil/memantine and phenobarbital
Donepezil/memantine's FDA label of December 17, 2024 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name donepezil/memantine. The donepezil/memantine label: “Inducers of CYP3A4 could increase the rate of elimination of donepezil.”
Check it at the source: the donepezil/memantine FDA label on DailyMed (effective December 17, 2024, Amneal Pharmaceuticals NY LLC); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the donepezil/memantine label say about phenobarbital?
Donepezil/memantine label, drug interactionsInducers of CYP3A4 (e.g., phenytoin, carbamazepine, dexamethasone, rifampin, and phenobarbital) could increase the rate of elimination of donepezil.
Source: FDA drug label (Memantine and Donepezil Hydrochlorides Extended-release), Amneal Pharmaceuticals NY LLC, effective December 17, 2024 (SPL set 2335950c-be3b-4248-ad04-e9763aee47d2), via openFDA; the full label on DailyMed
What does the phenobarbital label say about donepezil/memantine?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name donepezil/memantine in these sections. A label lists what its studies and reports found; it is not a complete list.
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
| Donepezil/memantine | Phenobarbital | |
|---|---|---|
| Labeled for | Alzheimer's disease | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $8.44 per unit 28-10 mg | $0.213 per tablet 100 mg tablet |
| Shortage now | A presentation being discontinued | 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