This article exists for one specific, important reason: to make sure the connection between nitric oxide, nitrate medications, and certain other drugs and substances is clearly and directly explained, in one place, separate from general wellness content.
The Real, Important Warning
If you take a nitrate medication (such as nitroglycerin), you should never combine it with erectile dysfunction medicines like sildenafil (Viagra) or tadalafil (Cialis) — the combination can cause a dangerous drop in blood pressure. Always follow your doctor’s or pharmacist’s guidance.
Why This Interaction Happens
Nitrate medications and PDE5-inhibitor medications (like sildenafil and tadalafil) both work, through different mechanisms, to relax and widen blood vessels. Taken separately, each is used under medical guidance for its own real purpose. Taken together, their blood-vessel-relaxing effects can combine in a way that drops blood pressure to a dangerous level — this is a well-established, real medical interaction, not a rare or theoretical risk.
Other Real Interactions Worth Knowing About
The medication interaction above is the single most acute danger, but it isn’t the only real interaction involving nitrate medications:
Alcohol. Drinking alcohol while taking a nitrate medication can add to its blood-pressure-lowering effect, increasing the risk of dizziness or fainting, especially when starting the medication, after a dose change, or after a gap in use. This is a real, documented caution — not the same severe, absolute danger as the ED-medication interaction, but a real reason to talk with your doctor or pharmacist about alcohol use if you’re on a nitrate medication.
Other blood-pressure medications. Combining nitrate medications with other blood-vessel-relaxing drugs — including calcium channel blockers, a common category of blood pressure medication — can also add to the blood-pressure-lowering effect in a way that’s been specifically documented to sometimes cause symptomatic drops in blood pressure. If you’re on more than one blood pressure or heart medication, your doctor or pharmacist is best positioned to check for this kind of combination.
A specialized medication called riociguat. This is a less commonly prescribed medication used for certain lung-related blood pressure conditions. It carries a real, officially recognized danger when combined with either nitrate medications or PDE5 inhibitors — similar in seriousness to the ED-medication warning above. Most readers of this article won’t be taking this specific medication, but if you are, this is a real, important interaction to be aware of alongside the others.
An Important Distinction
Food-based sources of nitric oxide support (like L-arginine-containing foods) are a different safety category than prescription nitrate medications for this specific interaction — but anyone on erectile-dysfunction or heart medication should still check with a doctor before starting a new supplement. This distinction matters: eating spinach is not the same real risk as taking a prescription nitrate medication. But if you’re on any heart or erectile-dysfunction medication and considering a nitric-oxide-related supplement specifically, that’s a real, separate reason to check with your doctor or pharmacist first — not because food-based sources carry the same risk, but because supplement dosing and interactions are less predictable than whole-food sources.
What This Article Is Not
This article is educational, not a substitute for guidance from your own doctor or pharmacist, who know your specific medications and health history. It does not cover every possible drug interaction, and it does not tell you what to do about your own specific medications — only your doctor or pharmacist can do that. It covers the real, well-documented interactions this cluster’s own research identified as most relevant and most safety-critical.
If You Take These Medications
Always tell every healthcare provider and pharmacist about every medication you take, including over-the-counter products, alcohol use, and supplements. If you have questions about this or any other medication interaction, talk with a doctor or pharmacist — they can review your specific situation in a way this article cannot.
References
- Schwartz, B. G., & Kloner, R. A. (2010). Drug interactions with phosphodiesterase-5 inhibitors used for the treatment of erectile dysfunction or pulmonary hypertension. Circulation, 122(1), 88–95. https://doi.org/10.1161/CIRCULATIONAHA.110.944603
- MedlinePlus (U.S. National Library of Medicine). Nitroglycerin Sublingual. https://medlineplus.gov/druginfo/meds/a601086.html
- Cleveland Clinic. Vasodilators. https://my.clevelandclinic.org/health/drugs/23207-vasodilators
- RxList. Adempas (riociguat). https://www.rxlist.com/adempas-drug.htm
About this article
Researched and written by: HealthUpward Editorial Team
Last updated: August 29, 2026
Evidence basis: Based on peer-reviewed research and reputable public health organizations cited within this article.
Medical review: This article has completed HealthUpward’s editorial review process. It has not been reviewed by a licensed healthcare professional.
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