What the FDA labels say about taking them together
Ganaxolone and phenobarbital
Ganaxolone's FDA label of November 28, 2025 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name ganaxolone. The ganaxolone label: “In patients on a stable ZTALMY dosage who are initiating or increasing the dosages of enzyme-inducing antiepileptic drugs, the ZTALMY dosage may need to be increased; …”
Check it at the source: the ganaxolone FDA label on DailyMed (effective November 28, 2025, Immedica Pharma US Inc); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the ganaxolone label say about phenobarbital?
Ganaxolone label, drug interactionsIn patients on a stable ZTALMY dosage who are initiating or increasing the dosages of enzyme-inducing antiepileptic drugs (e.g., carbamazepine, phenytoin, phenobarbital, and primidone), the ZTALMY dosage may need to be increased; however, do not exceed the maximum daily dosage of ZTALMY [see Dosage and Administration (2.1) ].
Source: FDA drug label (ZTALMY), Immedica Pharma US Inc, effective November 28, 2025 (SPL set d91612c4-b03a-4be4-a1ee-6a13e3b83d4e), via openFDA; the full label on DailyMed
What does the phenobarbital label say about ganaxolone?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name ganaxolone 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
| Ganaxolone | Phenobarbital | |
|---|---|---|
| Labeled for | n/a | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $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