Propranolol and Diltiazem Interaction
Drug interaction information between Propranolol and Diltiazem.
Propranolol and Diltiazem have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Propranolol and Diltiazem. 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
Both drugs slow down the heart and lower blood pressure. Taking them together can cause the heart to beat too slowly or lead to heart failure.
What To Do
Your doctor will need to check your heart rate and blood pressure regularly. Tell your doctor if you feel dizzy or short of breath.
FDA Label Information
Co-administration of propranolol and diltiazem in patients with cardiac disease has been associated with bradycardia, hypotension, high-degree heart block, and heart failure.
Propranolol Also Interacts With
- Clonidine minor
- Warfarin minor
- Verapamil minor
- Doxazosin minor
- Haloperidol minor
Diltiazem Also Interacts With
- Ezetimibe major
- Ezetimibe/Simvastatin major
- Simvastatin major
- Theophylline major
- Rifampin moderate
Frequently Asked Questions
Can I take Propranolol and Diltiazem together?
This is a minor interaction. Your doctor will need to check your heart rate and blood pressure regularly. Tell your doctor if you feel dizzy or short of breath.
How serious is the interaction between Propranolol and Diltiazem?
This interaction is classified as "minor" severity by the FDA. Minor interactions are unlikely to cause significant problems but should still be mentioned to your healthcare provider.
Why do Propranolol and Diltiazem interact?
Both drugs slow down the heart and lower blood pressure. Taking them together can cause the heart to beat too slowly or lead to heart failure.
Understanding the Propranolol and Diltiazem Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Propranolol belongs to the Non-Selective Beta-Blocker class and Diltiazem belongs to the Calcium Channel Blocker class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Both drugs slow down the heart and lower blood pressure. 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. Propranolol has 44 total documented interactions on file in this dataset, and Diltiazem has 46. 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: Your doctor will need to check your heart rate and blood pressure regularly. 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 Propranolol or Diltiazem 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.