ED pills and nitrates: why the combination is dangerous

In short: every FDA-approved ED pill carries the same hard rule. Sildenafil (Viagra), tadalafil (Cialis), vardenafil and avanafil (Stendra) must not be taken by anyone using nitrates, the chest-pain medicines such as nitroglycerin and isosorbide, and their patient leaflets add recreational “poppers” to the same list. Each label reports studies in which the pill strengthened the blood-pressure drop that nitrates cause, and the Cialis label’s patient counseling section warns that the combination could cause blood pressure “to suddenly drop to an unsafe level,” leading to dizziness, fainting, or even a heart attack or stroke (Cialis prescribing information, DailyMed). This page explains what nitrates are, why the combination is dangerous, what the labels say about timing, what to do if chest pain starts, and how a “natural” supplement can carry the same risk without telling you. Evidence level: label contraindications for all four drugs, backed by controlled blood-pressure studies in healthy men and men with angina.

What are nitrates?

Nitrates are heart medicines that widen blood vessels, most often used to treat or prevent angina, the chest pain caused by narrowed heart arteries. MedlinePlus, the National Library of Medicine’s drug guide, describes sublingual nitroglycerin as a vasodilator that “works by relaxing the blood vessels so the heart does not need to work as hard” (MedlinePlus: Nitroglycerin Sublingual). They come in more forms than many men expect: the Cialis and vardenafil patient leaflets list nitroglycerin in tablets, sprays, ointments, pastes and patches, plus isosorbide dinitrate and isosorbide mononitrate (Cialis prescribing information, DailyMed; vardenafil prescribing information, DailyMed).

If you are not sure whether something you take is a nitrate, the labels say to ask a prescriber or pharmacist. The question is worth asking before the first ED prescription, not after.

Why can’t nitrates be combined with ED pills?

Nitrates and ED pills push on the same blood-vessel relaxing pathway from two ends, so together they can lower blood pressure much further than either does alone. Nitrates release nitric oxide, which raises a messenger called cGMP that relaxes blood vessels; ED pills block PDE5, the enzyme that breaks cGMP down. The Viagra label states that, “consistent with its known effects on the nitric oxide/cGMP pathway,” sildenafil “was shown to potentiate the hypotensive effects of nitrates,” and it makes use with nitrates “in any form” a contraindication (Viagra prescribing information, DailyMed). Our explainer on sildenafil interactions covers the rest of that drug’s list.

The American Urological Association guideline puts it the same way: nitrates combined with a PDE5 inhibitor “can cause a precipitous drop in blood pressure,” and men taking nitrates regularly should not use these medicines (AUA erectile dysfunction guideline). The rule covers occasional use too. The labels say “regularly and/or intermittently,” so a nitroglycerin tablet kept for the odd episode of chest pain counts.

What do the four labels say?

The contraindication is the same across the class; what differs is how much each label says about timing. The table below summarizes section 4.1 and the related warnings of each current US label.

Sources: Viagra, Cialis, vardenafil and Stendra prescribing information, DailyMed. The tadalafil and avanafil intervals are instructions for emergency teams deciding whether a nitrate is medically necessary. They are not a waiting period that makes routine nitrate use safe, and the contraindication still stands.

Can you take sildenafil and nitroglycerin together?

No. Sildenafil and nitroglycerin are contraindicated together, and the label is unusually frank that no safe gap has been established: even though sildenafil blood levels at 24 hours are “much lower than at peak concentration, it is unknown whether nitrates can be safely co-administered at this time point” (Viagra prescribing information, DailyMed). The AUA guideline says men who carry sublingual nitroglycerin for angina should be advised not to use it within 24 hours of a PDE5 inhibitor, and possibly longer with a long-acting one such as tadalafil (AUA erectile dysfunction guideline).

The best timing data shows why caution beats arithmetic. In two controlled crossover studies from Edinburgh, sildenafil increased the blood-pressure drop from nitroglycerin only at the 1-hour mark in 33 healthy men, but in 20 men with stable angina the interaction lasted for at least 8 hours, the latest time tested in that group, although from 6 hours on it was on average no larger than the two drugs’ effects added together. The authors note that the 24-hour minimum “is not firmly evidence based” (Oliver et al., British Journal of Clinical Pharmacology, 2009). They describe the men with angina as the clinically relevant group, and that was the group in whom the interaction lasted longest.

Can you take Cialis and nitroglycerin together?

No. Tadalafil is contraindicated with any form of organic nitrate, and its patient leaflet notes that some of the active ingredient stays in the body for more than 2 days after a single tablet (Cialis prescribing information, DailyMed). In a crossover study of 150 men, nitroglycerin pushed standing systolic blood pressure below a preset threshold of 85 mm Hg in more men on tadalafil than on placebo when given 4, 8 and 24 hours after the last tadalafil dose, with no difference at 48 hours and beyond (Kloner et al., Journal of the American College of Cardiology, 2003). The Cialis label describes a 150-man study of this design and sets its 48-hour emergency interval from the results, while noting that at 48 hours a few more men on tadalafil than on placebo still had a larger blood-pressure drop.

Once-daily tadalafil changes the picture again. The label notes that daily use “provides continuous plasma tadalafil levels,” and tells prescribers to keep this in mind when weighing interactions, nitrates included (Cialis prescribing information, DailyMed). Our guide to tadalafil interactions covers the rest of its list.

What about poppers?

Poppers count as nitrates for this rule. The Viagra, Cialis, vardenafil and Stendra patient leaflets all tell men not to take the medicine if they use “poppers,” and between them they name amyl nitrite, amyl nitrate, butyl nitrite and butyl nitrate (Viagra prescribing information, DailyMed; Stendra prescribing information, DailyMed). The same blood-pressure risk applies, whatever the product claims to be.

Poppers are a hazard on their own as well. The FDA says they “have not been evaluated by the FDA for safe use,” are often sold as air fresheners, leather cleaners or nail polish removers, and can cause “extreme drops in blood pressure,” breathing problems, seizures, heart rhythm problems, coma and death (FDA Consumer Update on nitrite poppers). The agency’s 2021 advisory reported an increase in reports of deaths and hospitalizations, including blood-oxygen problems called methemoglobinemia, and advises consumers not to buy or use them (FDA advisory on nitrite poppers). Our page on lifestyle and ED covers the everyday habits that affect erections more broadly.

What if chest pain starts after taking an ED pill?

Stop, and get emergency medical help. The Viagra, Cialis and Stendra patient leaflets say to stop sexual activity and get medical help right away for chest pain, dizziness or nausea during sex, and the Cialis and Stendra labels add that men who have anginal chest pain after taking the pill “should seek immediate medical attention” (Cialis prescribing information, DailyMed; Stendra prescribing information, DailyMed). Do not decide on your own whether a nitrate is safe; the labels reserve that decision for a medical team with blood-pressure monitoring.

Tell the team which ED medicine you took and when. All four patient leaflets say that if you need emergency care for a heart problem, “it will be important for your healthcare provider to know when you last took” it. That single fact changes which treatments they can safely use. Men with heart disease can read more in our guide to ED and heart disease.

How can a supplement hide sildenafil?

Status: FDA warning: hidden drug ingredient found. Source: FDA Sexual Enhancement and Energy Product Notifications, checked 2026-10-17.

Some products sold as “all natural” sexual enhancement supplements contain real ED drugs that are not on the label. On October 15, 2026, the FDA reported that its laboratory confirmed a product called 10 Day Forecast “contains sildenafil and acetaminophen not listed on the product label,” and warned that it “may interact with nitrates found in some prescription drugs such as nitroglycerin and may lower blood pressure to dangerous levels” (FDA notification: 10 Day Forecast). A September 2026 notice found hidden tadalafil in another product and added that this “is especially concerning for people with diabetes, high blood pressure, high cholesterol or heart disease, who commonly take nitrate-containing medications” (FDA notification: Candy Power For Man).

The FDA’s list of these notices for sexual enhancement and energy products ran to 441 entries when we checked, and the agency says it covers “only a small fraction” of contaminated products, so a product missing from the list is not proof it is safe (FDA, Sexual Enhancement and Energy Product Notifications). It also warns that these products turn up in gas stations, convenience stores, supplement shops and big online marketplaces (FDA, Avoiding Products Contaminated with Hidden Ingredients). For a man on nitrates, that means the full interaction risk with no warning on the box. Our guide to FDA tainted supplement warnings explains how to check a product.

Does a heart condition rule out ED treatment?

Not automatically, but nitrates do, and the heart condition itself needs a clinician’s look first. The Viagra label says ED treatments “should not be generally used in men for whom sexual activity is inadvisable” because of their heart status, and that physicians should discuss the potential cardiac risk of sexual activity with patients who have cardiovascular risk factors (Viagra prescribing information, DailyMed). The Princeton IV consensus, from an interdisciplinary expert panel that met in 2023, built an algorithm for treating ED in men with coronary artery disease that specifically addresses nitrate use, and it points to newer studies suggesting the cardiovascular safety of PDE5 inhibitors (Kloner et al., Journal of Sexual Medicine, 2024).

For a man who needs nitrates, the answer is not to choose between the heart medicine and the ED pill on his own. NIDDK advises talking with a health care professional before using supplements for ED, and lists prolonged erections and vision or hearing loss after oral ED medicines as reasons to call right away (NIDDK, Treatment for ED). Our page on priapism covers the erection warning in detail.

When to talk to a clinician

Talk to the prescriber of your heart medicines, or the clinician treating your ED, before starting any ED pill if you have angina, carry nitroglycerin, use any patch, spray or tablet you are unsure about, or use poppers. Bring a complete list, including supplements and anything bought without a prescription. If you already take an ED medicine and are newly prescribed a nitrate, tell both prescribers. That conversation is where the decision belongs; this page is general information, not advice for your situation.

Sources

1. Viagra (sildenafil citrate) prescribing information, Pfizer, DailyMed
2. Cialis (tadalafil) prescribing information, Eli Lilly, DailyMed
3. Vardenafil hydrochloride tablets prescribing information, DailyMed
4. Stendra (avanafil) prescribing information, DailyMed
5. American Urological Association. Erectile Dysfunction: AUA Guideline (2018)
6. MedlinePlus: Nitroglycerin Sublingual
7. Oliver JJ, Kerr DM, Webb DJ. Time-dependent interactions of the hypotensive effects of sildenafil citrate and sublingual glyceryl trinitrate. Br J Clin Pharmacol. 2009
8. Kloner RA, et al. Time course of the interaction between tadalafil and nitrates. J Am Coll Cardiol. 2003
9. Kloner RA, et al. Princeton IV consensus guidelines: PDE5 inhibitors and cardiac health. J Sex Med. 2024
10. FDA. Ingesting or Inhaling Nitrite “Poppers” Can Cause Severe Injury or Death
11. FDA. FDA Advises Consumers Not to Purchase or Use Nitrite “Poppers” (2021)
12. FDA. Sexual Enhancement and Energy Product Notifications
13. FDA. 10 Day Forecast may be harmful due to hidden ingredients (2026)
14. FDA. Candy Power For Man may be harmful due to hidden ingredient (2026)
15. FDA. Avoiding Products Contaminated with Hidden Ingredients
16. NIDDK. Treatment for Erectile Dysfunction