Short answer: ED pills (sildenafil, tadalafil, vardenafil and avanafil) must not be taken with nitrate medicines. Both types of drug widen blood vessels, and together they can cause a sudden, severe fall in blood pressure that may lead to fainting, a heart attack or a stroke. If you take a nitrate for chest pain, an ED pill is not safe for you unless a cardiologist has specifically advised otherwise.

Why the combination is dangerous

Nitrates, such as glyceryl trinitrate (GTN or nitroglycerin), release nitric oxide in the body. Nitric oxide raises a chemical messenger called cGMP, which relaxes smooth muscle in blood vessel walls and lowers blood pressure. PDE5 inhibitors, the group that includes all common ED pills, block the enzyme that breaks cGMP down.

Taken together, cGMP rises far more than either drug would cause alone. The result is excessive widening of blood vessels throughout the body. Blood pressure can fall rapidly, which reduces blood flow to the heart and brain. For someone who already has coronary artery disease, that drop can be life-threatening. This is why every ED pill label lists nitrates as a contraindication, meaning the combination should not be used.

Which medicines contain nitrates?

Nitrates are used to prevent or relieve angina (chest pain caused by reduced blood flow to the heart) and sometimes in heart failure. They come in several forms:

• Glyceryl trinitrate (GTN, nitroglycerin): tablets or sprays placed under the tongue, patches, ointment and some infusions.
• Isosorbide mononitrate: a regular tablet taken daily to prevent angina.
• Isosorbide dinitrate: tablets used for prevention and treatment of angina.
• Nicorandil: not strictly a nitrate, but it has a nitrate-like action and its prescribing information also advises against using it with PDE5 inhibitors.

Recreational inhaled products known as “poppers” (amyl or alkyl nitrites) also act in the same way. Using them with an ED pill carries the same risk of a dangerous blood pressure drop.

If you are not sure whether a medicine is a nitrate, check the active ingredient on the label or ask a pharmacist. Brand names can be confusing, and some heart medicines look similar to others that are safe.

How long should you wait?

There is no safe overlap, but doctors do talk about waiting times in emergencies. According to U.S. prescribing information, nitrates should not be used within 24 hours of sildenafil or vardenafil, within 48 hours of tadalafil, and within 12 hours of avanafil. Those figures are minimum gaps used by doctors in emergency situations, not a green light to combine the medicines casually. The longer-acting the ED pill, the longer the caution lasts.

If you take a nitrate regularly, you should not be taking an ED pill at all without your cardiologist’s explicit guidance. Some men can switch to a different heart treatment that does not contain a nitrate, but only a specialist can make that decision.

What to do if chest pain happens after an ED pill

1. Call emergency services immediately. Do not wait to see whether it settles.
2. Tell the responders and the hospital exactly what you took and when, including the name of the ED pill and the time of the dose. This information changes how doctors treat chest pain, because a nitrate could be dangerous at that point.
3. Do not take your own nitrate spray or tablet unless emergency staff advise you to after hearing which ED pill you used.
4. Sit or lie down, and avoid standing up suddenly if you feel faint.

Many men carry a medical alert card or a note on their phone listing their medicines. If you use ED pills occasionally, adding them to that list can help paramedics make safe decisions.

Warning signs of a dangerous blood pressure drop

• Severe dizziness or light-headedness, especially on standing
• Fainting or near-fainting
• Chest pain, tightness or pressure
• Rapid or irregular heartbeat
• Pale, cold, clammy skin
• Confusion, blurred vision or difficulty speaking

Any of these after taking an ED pill is a reason to seek urgent medical care, particularly if you also have heart disease or use a nitrate.

Other medicines that need care with ED pills

Nitrates are the most dangerous interaction, but not the only one. Other combinations that need medical advice include:

• Riociguat (used for pulmonary hypertension), which is also contraindicated.
• Alpha-blockers used for prostate symptoms or blood pressure, which can add to blood pressure lowering.
• Other blood pressure medicines, particularly in people with already low readings.
• Certain antifungals, antibiotics and HIV medicines that raise ED pill levels in the blood.
• Other PDE5 inhibitors; do not combine two ED pills.

Always bring a full medicine list, including over-the-counter products and supplements, to any appointment about erectile dysfunction.

Heart health and erections are connected

Difficulty with erections can be an early sign of problems in blood vessels, including heart disease, high blood pressure and diabetes. The arteries in the penis are small and may show reduced flow before larger arteries cause symptoms. That is one reason doctors often check heart risk when a man reports new ED. Read more in how blood pressure affects erections and our complete guide to erectile dysfunction.

If you have angina, have had a heart attack or stroke, or have been told you have heart disease, speak with your cardiologist before using any ED pill. Sexual activity itself is also moderate exercise, and doctors assess whether your heart can safely handle it. Our article on when to see a doctor for erectile dysfunction explains how to raise the subject.

Practical steps to stay safe

• Tell every prescriber and pharmacist about all the medicines you take, including ED pills.
• Do not borrow or share ED tablets; the person you share with may use a nitrate.
• Check labels on heart medicines for words such as “nitrate”, “nitroglycerin”, “isosorbide” or “nicorandil”.
• Keep a written medicine list in your wallet or phone.
• Ask about non-drug options and lifestyle measures, such as those in our guide to lifestyle changes to improve erectile dysfunction.
• Look at all your treatment choices in our overview of the best medicines and treatments for erectile dysfunction.

Before using any product, read the full label and leaflet. Our drug policy and FAQs describe how we handle medicine information, and you can read about each medicine type in our sildenafil and tadalafil categories.

Frequently asked questions

Can I take an ED pill if I only use nitroglycerin occasionally?

No, not without medical advice. Even occasional nitrate use is a reason to avoid ED pills, because a nitrate may be needed in an emergency and would be dangerous after an ED pill.

Is it safe to take a nitrate a day after an ED pill?

Waiting times exist for emergencies, but they are not a plan for routine use. The gap depends on the ED pill, from about 12 hours for avanafil to about 48 hours for tadalafil, and a doctor should decide.

What if I am not sure whether my heart medicine is a nitrate?

Ask your pharmacist or doctor before taking an ED pill. Do not guess from the name.

Are herbal “natural” ED products safer with nitrates?

Not necessarily. Some products sold as supplements have been found to contain hidden sildenafil or similar drugs, which would carry the same interaction risk.

Can women or people who do not have ED be affected?

Yes. The interaction is about the drugs, not the reason for taking them. PDE5 inhibitors are also used for pulmonary hypertension, and the same nitrate warning applies.

Conclusion

ED pills and nitrates should never be used together because both lower blood pressure by the same pathway, and the combined effect can be sudden and severe. If you take any nitrate, or you are unsure, speak to your doctor or pharmacist before using an ED pill. In an emergency, tell medical staff exactly which ED pill you took and when.

References

• U.S. FDA prescribing information for Viagra, Cialis, Levitra and Stendra.
• NHS: Sildenafil and tadalafil medicine information, interactions with nitrates.

This article is general education, not individual medical advice. It has not been written as a substitute for a consultation with a licensed healthcare professional.