What the FDA labels say about taking them together
Osilodrostat and phenobarbital
Osilodrostat's FDA label of November 18, 2025 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name osilodrostat. The osilodrostat label: “Concomitant use of ISTURISA with strong CYP3A4 and/or CYP2B6 inducers may cause a decrease in osilodrostat concentration and may reduce the efficacy of ISTURISA. …”
Check it at the source: the osilodrostat FDA label on DailyMed (effective November 18, 2025, Recordati Rare Diseases, Inc.); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the osilodrostat label say about phenobarbital?
Osilodrostat label, drug interactionsCYP3A4 and CYP2B6 Inducers Clinical Impact: Concomitant use of ISTURISA with strong CYP3A4 and/or CYP2B6 inducers (…) may cause a decrease in osilodrostat concentration and may reduce the efficacy of ISTURISA. Discontinuation of strong CYP3A4 and/or CYP2B6 inducers while using ISTURISA may cause an increase in osilodrostat concentration and may increase the risk of … Intervention: During concomitant use of ISTURISA with strong CYP3A4 and CYP2B6 inducers, monitor cortisol concentration and patient's signs and symptoms. An increase in ISTURISA dosage may be needed. …
Source: FDA drug label (Isturisa), Recordati Rare Diseases, Inc., effective November 18, 2025 (SPL set f3a5ec24-63c3-4d83-b1c0-6c550fbe7ae2), via openFDA; the full label on DailyMed
What does the phenobarbital label say about osilodrostat?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name osilodrostat 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
| Osilodrostat | 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