Nitroglycerin and Heparin Interaction
Drug interaction information between Nitroglycerin and Heparin.
Nitroglycerin and Heparin have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Nitroglycerin and Heparin. 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
Nitroglycerin can make heparin less effective at thinning the blood, which changes how quickly the blood clots.
What To Do
Your doctor should check your blood clotting levels often and may need to change your heparin dose while you are taking both drugs.
FDA Label Information
Intravenous nitroglycerin administered to heparinized patients may result in a decrease of the partial thromboplastin time with subsequent rebound effect upon discontinuation of nitroglycerin. Careful monitoring of partial thromboplastin time and adjustment of heparin dosage are recommended during coadministration of heparin and intravenous nitroglycerin.
Nitroglycerin Also Interacts With
- Dapsone Topical moderate
- Lidocaine Topical moderate
- Aspirin minor
- Sildenafil minor
- Tadalafil minor
Heparin Also Interacts With
- Ibuprofen moderate
- Celecoxib moderate
- Hydroxychloroquine moderate
- Indomethacin moderate
- Dipyridamole moderate
Frequently Asked Questions
Can I take Nitroglycerin and Heparin together?
This is a minor interaction. Your doctor should check your blood clotting levels often and may need to change your heparin dose while you are taking both drugs.
How serious is the interaction between Nitroglycerin and Heparin?
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 Nitroglycerin and Heparin interact?
Nitroglycerin can make heparin less effective at thinning the blood, which changes how quickly the blood clots.
Understanding the Nitroglycerin and Heparin Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Nitroglycerin belongs to the Nitrate Vasodilator class and Heparin belongs to the Unfractionated Heparin class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Nitroglycerin can make heparin less effective at thinning the blood, which changes how quickly the blood clots. 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. Nitroglycerin has 8 total documented interactions on file in this dataset, and Heparin has 20. 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 should check your blood clotting levels often and may need to change your heparin dose while you are taking both drugs. 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 Nitroglycerin or Heparin 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.