What the FDA labels say about taking them together
Folic acid and primidone
Folic acid's FDA label of July 24, 2026 names primidone in its drug interactions section; the primidone label PlainMeds reads does not name folic acid. The folic acid label: “… metabolism; the administration of anticonvulsants, such as diphenylhydantoin, primidone, and barbiturates; alcohol consumption and, especially, alcoholic cirrhosis; …”
Check it at the source: the folic acid FDA label on DailyMed (effective July 24, 2026, Rising Pharma Holdings, Inc.); the primidone FDA label on DailyMed (effective September 10, 2026, Bausch Health US, LLC).
What does the folic acid label say about primidone?
Folic acid label, drug interactionsFolate deficiency may result from increased loss of folate, as in renal dialysis and/or interference with metabolism (e.g., folic acid antagonists such as methotrexate); the administration of anticonvulsants, such as diphenylhydantoin, primidone, and barbiturates; alcohol consumption and, especially, alcoholic cirrhosis; and the administration of pyrimethamine and nitrofurantoin.
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 primidone label say about folic acid?
Primidone's label (effective September 10, 2026) does 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 (Mysoline), NDA009170 (Valeant), as published by Bausch Health US, LLC, effective September 10, 2026 (SPL set af593171-dabb-4ea3-b44c-89ed457b2c46), 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 | Primidone | |
|---|---|---|
| Labeled for | n/a | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0201 per tablet 1 mg tablet | $0.0914 per tablet 50 mg tablet |
| Shortage now | No current entry | 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