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. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
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.
What To Do
Avoid taking these two drugs together. Your doctor may need to switch you to a different blood pressure medication.
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
Can I take Nifedipine and Phenytoin together?
This is a moderate interaction. Avoid taking these two drugs together. Your doctor may need to switch you to a different blood pressure medication.
How serious is the interaction between Nifedipine and Phenytoin?
This interaction is classified as "moderate" severity by the FDA. Moderate interactions may worsen your condition or change how your medications work.
Why do Nifedipine and Phenytoin 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.
Understanding the Nifedipine and Phenytoin Interaction
FDA-approved prescribing information for these two drugs flags their combination as a moderate-severity interaction. Nifedipine belongs to the Calcium Channel Blocker class and Phenytoin belongs to the Anticonvulsant (Hydantoin) class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Phenytoin makes your body get rid of nifedipine much faster than normal. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Nifedipine has 26 total documented interactions on file in this dataset, and Phenytoin has 147. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Avoid taking these two drugs together. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Nifedipine or Phenytoin based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.