What the FDA labels say about taking them together
Buspirone and phenobarbital
Buspirone's FDA label of December 22, 2023 names phenobarbital in its drug interactions section; the phenobarbital 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 phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the buspirone label say about phenobarbital?
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 phenobarbital label say about buspirone?
Phenobarbital's label (effective August 27, 2026) 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 (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
| Buspirone | Phenobarbital | |
|---|---|---|
| Labeled for | Anxiety | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.043 per tablet 15 mg tablet | $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