What the FDA labels say about taking them together
Phenytoin and quinine
Quinine's FDA label of November 9, 2023 names phenytoin in its drug interactions (prescription label) section; the phenytoin 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 phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.); the quinine FDA label on DailyMed (effective November 9, 2023).
What does the phenytoin label say about quinine?
Phenytoin's label (effective October 15, 2024) 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 (Phenytek), Mylan Pharmaceuticals Inc., effective October 15, 2024 (SPL set 0f94c791-8b07-4b41-927e-c9f28bec5f60), via openFDA; the full label on DailyMed
What does the quinine label say about phenytoin?
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
| Phenytoin | Quinine | |
|---|---|---|
| Labeled for | Seizures and epilepsy | n/a |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.145 per capsule 100 mg capsule | $0.698 per capsule 324 mg capsule |
| Shortage now | No current entry | 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