What the FDA labels say about taking them together
Doxercalciferol and phenobarbital
Doxercalciferol's FDA label of October 23, 2025 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name doxercalciferol. The doxercalciferol label: “… affect the 25-hydroxylation of doxercalciferol. Examples Glutethimide and phenobarbital Intervention If a patient initiates or discontinues therapy with an enzyme inducer, dose adjustment of doxercalciferol may be …”
Check it at the source: the doxercalciferol FDA label on DailyMed (effective October 23, 2025, Eugia US LLC); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the doxercalciferol label say about phenobarbital?
Doxercalciferol label, drug interactionsEnzyme Inducers Clinical Impact Doxercalciferol is activated by CYP 27 in the liver. Enzyme inducers may affect the 25-hydroxylation of doxercalciferol [see Clinical Pharmacology (12.3) ]. Examples Glutethimide and phenobarbital Intervention If a patient initiates or discontinues therapy with an enzyme inducer, dose adjustment of doxercalciferol may be necessary. Monitor intact PTH and serum calcium concentrations closely.
Source: FDA drug label (Doxercalciferol), Eugia US LLC, effective October 23, 2025 (SPL set 3376536b-043d-478a-b129-7ce11ec94e3e), via openFDA; the full label on DailyMed
What does the phenobarbital label say about doxercalciferol?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name doxercalciferol 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
| Doxercalciferol | 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 | A presentation being discontinued | 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