What the FDA labels say about taking them together
Buspirone and phenytoin
Buspirone's FDA label of December 22, 2023 names phenytoin in its drug interactions section; the phenytoin labels PlainMeds reads (2) do not name buspirone. The buspirone label: “Other Inhibitors and Inducers of CYP3A4 Substances that inhibit CYP3A4, such as ketoconazole or ritonavir, may inhibit buspirone metabolism and increase plasma concentrations of buspirone while substances that induce …”
Check it at the source: the buspirone FDA label on DailyMed (effective December 22, 2023, Unichem Pharmaceuticals (USA), Inc.); the phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the buspirone label say about phenytoin?
Buspirone label, drug interactionsOther Inhibitors and Inducers of CYP3A4 Substances that inhibit CYP3A4, such as ketoconazole or ritonavir, may inhibit buspirone metabolism and increase plasma concentrations of buspirone while substances that induce CYP3A4, such as dexamethasone or certain anticonvulsants (phenytoin, phenobarbital, carbamazepine), may increase the rate of buspirone metabolism.
Source: FDA drug label (Buspirone Hydrochloride), Unichem Pharmaceuticals (USA), Inc., effective December 22, 2023 (SPL set a6bdf140-075e-445e-a62d-633a4b97f3a8), via openFDA; the full label on DailyMed
What does the phenytoin label say about buspirone?
Phenytoin's label (effective October 15, 2024) and its 1 other brand-application label do not name buspirone 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
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
| Buspirone | Phenytoin | |
|---|---|---|
| Labeled for | Anxiety | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.043 per tablet 15 mg tablet | $0.145 per capsule 100 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