Nifedipine and Phenytoin Interaction
Drug interaction information between Nifedipine and Phenytoin.
Nifedipine and Phenytoin have a documented moderate interaction in FDA labeling.
FDA drug labeling documents a moderate-severity interaction between Nifedipine 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
Phenytoin makes your body get rid of nifedipine much faster than normal. This prevents the blood pressure medicine from working as well as it should.
FDA Label Information
Co-administration of nifedipine with phenytoin, an inducer of CYP3A4, lowers the systemic exposure to nifedipine by approximately 70%. Avoid co-administration of nifedipine with phenytoin or any known CYP3A4 inducer or consider an alternative antihypertensive therapy.
Nifedipine Also Interacts With
- Theophylline major
- Nirmatrelvir/Ritonavir moderate
- Tacrolimus Topical moderate
- Fluoxetine minor
- Fluconazole 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 Nifedipine + Phenytoin?
Compiled FDA labeling labels this pair moderate. 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 Nifedipine's 26. In the moderate band specifically: Nifedipine has 3 (also Nirmatrelvir/Ritonavir, Tacrolimus Topical); Phenytoin has 23 (also Apixaban, Aprepitant, Canagliflozin, Carbidopa/Levodopa).
What mechanism field is on file for Nifedipine and Phenytoin?
Phenytoin makes your body get rid of nifedipine much faster than normal. This prevents the blood pressure medicine from working as well as it should.
Phenytoin carries more major-labeled pairs than Nifedipine
SPL source-record counts only. This page's band is moderate · classes on file: Nifedipine (Calcium Channel Blocker); Phenytoin (Anticonvulsant (Hydantoin)).
Phenytoin has 4 major-labeled pairs vs Nifedipine's 1. This page itself is in the moderate band, not the major band.
1 major · 3 moderate · 22 minor · 26 total
- Other moderate peers for Nifedipine
- Nirmatrelvir/Ritonavir
- Tacrolimus Topical
4 major · 23 moderate · 120 minor · 147 total
- Other moderate peers for Phenytoin
- Apixaban
- Aprepitant
- Canagliflozin
- Carbidopa/Levodopa
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.