What the FDA labels say about taking them together
Calcitriol and phenytoin
Calcitriol's FDA label (Calcitriol) of July 10, 2026 names phenytoin in its drug interactions section; the phenytoin 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 phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the calcitriol label say about phenytoin?
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 phenytoin label say about calcitriol?
Phenytoin's label (effective October 15, 2024) 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 (Phenytek), Mylan Pharmaceuticals Inc., effective October 15, 2024 (SPL set 0f94c791-8b07-4b41-927e-c9f28bec5f60), 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 | Phenytoin | |
|---|---|---|
| Labeled for | Psoriasis | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.153 per capsule 0.25 mcg capsule | $0.145 per capsule 100 mg capsule |
| Shortage now | A presentation being discontinued | No current entry |
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