What the FDA labels say about taking them together
Phenobarbital and quinine
Quinine's FDA label of November 9, 2023 names phenobarbital in its drug interactions (prescription label) section; the phenobarbital labels PlainMeds reads (2) do not name quinine. The quinine label: “Antiepileptics (AEDs) Carbamazepine, phenobarbital, and phenytoin are CYP3A4 inducers and may decrease quinine plasma concentrations if used concurrently with quinine sulfate.”
Check it at the source: the phenobarbital FDA label on DailyMed (effective August 27, 2026); the quinine FDA label on DailyMed (effective November 9, 2023).
What does the phenobarbital label say about quinine?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name quinine 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
What does the quinine label say about phenobarbital?
Quinine label, drug interactions (prescription label)Antiepileptics (AEDs) (Carbamazepine, Phenobarbital, and Phenytoin) Carbamazepine, phenobarbital, and phenytoin are CYP3A4 inducers and may decrease quinine plasma concentrations if used concurrently with quinine sulfate.
Source: FDA drug label (Chininum sulphuricum), Boiron, effective November 9, 2023 (SPL set 33885950-2a55-11e7-8288-424c58303031), 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
| Phenobarbital | Quinine | |
|---|---|---|
| Labeled for | Seizures and epilepsy | n/a |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.213 per tablet 100 mg tablet | $0.698 per capsule 324 mg capsule |
| Shortage now | A presentation being discontinued | No current entry |
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