What the FDA labels say about taking them together
Exemestane and phenobarbital
Exemestane's FDA label of September 12, 2024 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name exemestane. The exemestane label: “Drugs That Induce CYP 3A4 Co-medications that induce CYP 3A4 may significantly decrease exposure to exemestane.”
Check it at the source: the exemestane FDA label on DailyMed (effective September 12, 2024, Breckenridge Pharmaceutical, Inc.); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the exemestane label say about phenobarbital?
Exemestane label, drug interactionsDrugs That Induce CYP 3A4 Co-medications that induce CYP 3A4 (e.g., rifampicin, phenytoin, carbamazepine, phenobarbital, or St. John's Wort) may significantly decrease exposure to exemestane.
Source: FDA drug label (Exemestane), Breckenridge Pharmaceutical, Inc., effective September 12, 2024 (SPL set 4e3fd382-19f5-4ded-ab22-39d5b1b2f366), via openFDA; the full label on DailyMed
What does the phenobarbital label say about exemestane?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name exemestane 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
| Exemestane | Phenobarbital | |
|---|---|---|
| Labeled for | Breast cancer | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.748 per tablet 25 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