What the FDA labels say about taking them together
Calcitriol and phenobarbital
Calcitriol's FDA label (Calcitriol) of July 10, 2026 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name calcitriol. The calcitriol label: “Phenytoin/Phenobarbital The coadministration of phenytoin or phenobarbital will not affect plasma concentrations of calcitriol, but may reduce endogenous plasma levels of 25(OH)D 3 by accelerating metabolism.”
Check it at the source: the calcitriol FDA label on DailyMed (effective October 23, 2024, Amneal Pharmaceuticals LLC); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the calcitriol label say about phenobarbital?
Calcitriol label (ANI Pharmaceuticals, Inc., July 10, 2026), drug interactionsPhenytoin/Phenobarbital The coadministration of phenytoin or phenobarbital will not affect plasma concentrations of calcitriol, but may reduce endogenous plasma levels of 25(OH)D 3 by accelerating metabolism.
Source: FDA drug label (Calcitriol, NDA021068), ANI Pharmaceuticals, Inc., effective July 10, 2026 (SPL set bdb9c0d4-bdb3-4174-a4d9-55c423f38476), via openFDA
Source: FDA drug label (Calcitriol), Amneal Pharmaceuticals LLC, effective October 23, 2024 (SPL set b1fef137-63c5-4662-8cd9-b9e8b12bacb6), via openFDA; the full label on DailyMed
What does the phenobarbital label say about calcitriol?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name calcitriol 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
| Calcitriol | Phenobarbital | |
|---|---|---|
| Labeled for | Psoriasis | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.153 per capsule 0.25 mcg capsule | $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