Phenobarbital and Ranolazine Interaction
Drug interaction information between Phenobarbital and Ranolazine.
Phenobarbital and Ranolazine have a documented major interaction in FDA labeling.
FDA drug labeling documents a major-severity interaction between Phenobarbital and Ranolazine. 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
Phenobarbital triggers your liver to process ranolazine too quickly, meaning there won't be enough medicine in your blood.
What To Do
Do not take these two drugs together.
FDA Label Information
CYP3A Inducers Do not use ranolazine with CYP3A inducers such as rifampin, rifabutin, rifapentine, phenobarbital, phenytoin, carbamazepine, and St.
Phenobarbital Also Interacts With
- Nirmatrelvir/Ritonavir major
- Voriconazole major
- Canagliflozin moderate
- Cenobamate moderate
- Clarithromycin moderate
Ranolazine Also Interacts With
- Ketoconazole major
- Carbamazepine major
- Clarithromycin major
- Rifampin major
- Phenytoin major
Frequently Asked Questions
Can I take Phenobarbital and Ranolazine together?
This is a major interaction. Do not take these two drugs together.
How serious is the interaction between Phenobarbital and Ranolazine?
This interaction is classified as "major" severity by the FDA. Major interactions may be life-threatening or cause serious side effects.
Why do Phenobarbital and Ranolazine interact?
Phenobarbital triggers your liver to process ranolazine too quickly, meaning there won't be enough medicine in your blood.
Understanding the Phenobarbital and Ranolazine Interaction
FDA-approved prescribing information for these two drugs flags their combination as a major-severity interaction. Phenobarbital belongs to the Anticonvulsant (Barbiturate) class and Ranolazine belongs to the Late Sodium Current Inhibitor (Antianginal) class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Phenobarbital triggers your liver to process ranolazine too quickly, meaning there won't be enough medicine in your blood. 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. Phenobarbital has 59 total documented interactions on file in this dataset, and Ranolazine has 31. 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: Do not take 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 Phenobarbital or Ranolazine 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.