Phenytoin and Ranolazine Interaction
Drug interaction information between Phenytoin and Ranolazine.
Phenytoin and Ranolazine have a documented major interaction in FDA labeling.
FDA drug labeling documents a major-severity interaction between Phenytoin and Ranolazine. 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 clear ranolazine much faster than it should, which lowers the drug's effectiveness.
FDA Label Information
CYP3A Inducers Do not use ranolazine with CYP3A inducers such as rifampin, rifabutin, rifapentine, phenobarbital, phenytoin, carbamazepine, and St.
Phenytoin Also Interacts With
- Nirmatrelvir/Ritonavir major
- Posaconazole major
- Voriconazole major
- Apixaban moderate
- Aprepitant moderate
Ranolazine Also Interacts With
- Ketoconazole major
- Carbamazepine major
- Clarithromycin major
- Rifampin major
- Phenobarbital major
Frequently Asked Questions
What SPL severity band is on file for Phenytoin + Ranolazine?
Compiled FDA labeling labels this pair major. 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 Ranolazine's 31. In the major band specifically: Phenytoin has 4 (also Nirmatrelvir/Ritonavir, Posaconazole, Voriconazole); Ranolazine has 12 (also Ketoconazole, Carbamazepine, Clarithromycin, Rifampin).
What mechanism field is on file for Phenytoin and Ranolazine?
Phenytoin makes your body clear ranolazine much faster than it should, which lowers the drug's effectiveness.
Ranolazine carries more major-labeled pairs than Phenytoin
SPL source-record counts only. This page's band is major · classes on file: Phenytoin (Anticonvulsant (Hydantoin)); Ranolazine (Late Sodium Current Inhibitor (Antianginal)).
Ranolazine has 12 major-labeled pairs vs Phenytoin's 4.
4 major · 23 moderate · 120 minor · 147 total
- Other major peers for Phenytoin
- Nirmatrelvir/Ritonavir
- Posaconazole
- Voriconazole
12 major · 7 moderate · 12 minor · 31 total
- Other major peers for Ranolazine
- Ketoconazole
- Carbamazepine
- Clarithromycin
- Rifampin
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.