What the FDA labels say about taking them together
Folic acid and phenobarbital
Folic acid's FDA label (Folic Acid) of February 11, 2026 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name folic acid. The folic acid label: “Enzyme-inducing anticonvulsants such as phenytoin, primidone, carbamazepine, phenobarbital, and the broader anticonvulsant class increase hepatic folate metabolism, inhibit intestinal folate-processing enzymes, raise …”
Check it at the source: the folic acid FDA label on DailyMed (effective July 24, 2026, Rising Pharma Holdings, Inc.); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the folic acid label say about phenobarbital?
Folic Acid label (Ayurax, LLC, February 11, 2026), drug interactionsEnzyme-inducing anticonvulsants such as phenytoin, primidone, carbamazepine, phenobarbital, and the broader anticonvulsant class increase hepatic folate metabolism, inhibit intestinal folate-processing enzymes, raise gastrointestinal pH, or displace folate from serum proteins, collectively leading to decreased folate availability.
Source: FDA drug label (Folic Acid, NDA216395), Ayurax, LLC, effective February 11, 2026 (SPL set 96618bf8-6c03-4df3-9896-b7ef27ca392a), via openFDA
Source: FDA drug label (Folic Acid), Rising Pharma Holdings, Inc., effective July 24, 2026 (SPL set 0baa10dd-6d1d-4946-8236-566451132da3), via openFDA; the full label on DailyMed
What does the phenobarbital label say about folic acid?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name folic acid 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
| Folic acid | Phenobarbital | |
|---|---|---|
| Labeled for | n/a | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0201 per tablet 1 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