Folic Acid and Phenytoin Interaction
Drug interaction information between Folic Acid and Phenytoin.
Folic Acid and Phenytoin have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Folic Acid and Phenytoin. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Taking these two together can cause the levels of both drugs in your blood to drop, making them both less effective.
Folic Acid Also Interacts With
- Dapsone Topical minor
- Infliximab minor
- Methotrexate minor
- Prenatal Multivitamin minor
Phenytoin Also Interacts With
- Nirmatrelvir/Ritonavir major
- Posaconazole major
- Ranolazine major
- Voriconazole major
- Apixaban moderate
Frequently Asked Questions
What SPL severity band is on file for Folic Acid + Phenytoin?
Compiled FDA labeling labels this pair minor. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Phenytoin has 147 labeled pairs on file vs Folic Acid's 5. In the minor band specifically: Folic Acid has 5 (also Dapsone Topical, Infliximab, Methotrexate, Prenatal Multivitamin); Phenytoin has 120 (also Atorvastatin, Omeprazole, Simvastatin, Methylphenidate).
What mechanism field is on file for Folic Acid and Phenytoin?
Taking these two together can cause the levels of both drugs in your blood to drop, making them both less effective.
Phenytoin carries more major-labeled pairs than Folic Acid
SPL source-record counts only. This page's band is minor · classes on file: Folic Acid (B Vitamin (Folate) Supplement); Phenytoin (Anticonvulsant (Hydantoin)).
Phenytoin has 4 major-labeled pairs vs Folic Acid's 0. This page itself is in the minor band, not the major band.
0 major · 0 moderate · 5 minor · 5 total
- Other minor peers for Folic Acid
- Dapsone Topical
- Infliximab
- Methotrexate
- Prenatal Multivitamin
4 major · 23 moderate · 120 minor · 147 total
- Other minor peers for Phenytoin
- Atorvastatin
- Omeprazole
- Simvastatin
- Methylphenidate
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.