PDE5 Inhibitor & Nitrate Safety Checker
Check Your Safety Window
This tool helps you determine if it's safe to take nitrate medications after taking a PDE5 inhibitor (like Viagra or Cialis).
Please select your medication and time elapsed to see safety status
If you're taking medication for erectile dysfunction and also use nitrates for chest pain, you could be in serious danger - even if you think you're being careful. This isn't a rare edge case. It's a well-documented, life-threatening interaction that has sent people to the ER, caused heart attacks, and led to lawsuits. And yet, many patients still don't know about it.
What Are PDE5 Inhibitors and Nitrates?
PDE5 inhibitors are a class of drugs used primarily to treat erectile dysfunction (ED) and, in some cases, pulmonary arterial hypertension. The most common ones are sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra), and avanafil (Stendra). They work by relaxing blood vessels to increase blood flow - which helps with erections but also affects the rest of your body.
Nitrates are medications like nitroglycerin (often given as a spray or pill under the tongue), isosorbide dinitrate, or isosorbide mononitrate. They're used to treat angina - chest pain caused by reduced blood flow to the heart. Nitrates work by releasing nitric oxide, which widens blood vessels and lowers blood pressure to relieve heart strain.
On their own, both types of drugs are safe when used correctly. But together? They create a perfect storm.
Why the Combination Is Deadly
Hereâs the science behind the danger, simplified. Both PDE5 inhibitors and nitrates boost a chemical in your body called cGMP. Nitrates make more of it. PDE5 inhibitors stop your body from breaking it down. The result? A massive, uncontrolled surge of cGMP that causes your blood vessels to relax way too much.
This leads to a sudden, dramatic drop in blood pressure - sometimes by 30 mmHg or more. In one study, 27% of people who took sildenafil with nitroglycerin saw their systolic blood pressure plunge below 85 mmHg while standing. Thatâs low enough to cause dizziness, fainting, or worse.
And it doesnât take long. The drop can happen within minutes. You might feel fine after taking your ED pill, then take your nitroglycerin for chest pain later - and suddenly collapse. Thereâs no warning sign, no gradual decline. Just a rapid, dangerous fall.
Not All PDE5 Inhibitors Are the Same
Some PDE5 inhibitors are riskier than others. Sildenafil (Viagra) and vardenafil (Levitra) have shorter half-lives - around 4 to 5 hours - but they still cause severe drops when mixed with nitrates. Avanafil (Stendra) has a slightly faster onset and shorter duration, and some studies suggest it might cause slightly less of a blood pressure drop. But hereâs the catch: even with avanafil, 24% of patients still had dangerous drops compared to placebo.
Tadalafil (Cialis) is the worst offender in terms of duration. It stays in your system for up to 36 hours. That means if you take Cialis on Monday night, you still shouldnât use nitroglycerin until Wednesday morning. Many people donât realize this. They think, âI took it yesterday - Iâm fine.â But the drug is still active.
And itâs not just prescription nitrates. Recreational drugs like âpoppersâ (amyl nitrite) are also nitrates. Theyâre often used for sexual enhancement, especially among men who have sex with men. Combining poppers with PDE5 inhibitors has led to multiple emergency room visits - and deaths. Yet, many users donât connect the two.
Real-World Cases Show the Gap in Care
Despite decades of warnings, doctors still miss this interaction. A 2022 review of U.S. medical records found that 1 to 4% of men taking PDE5 inhibitors were also prescribed nitrates. Of those, only 27% received any warning about the danger.
On Reddit, users share stories that sound like they came from a medical textbook:
- âI took nitroglycerin 12 hours after sildenafil. My cardiologist said it was fine. I passed out in the shower.â - u/CardioPatient87
- âMy urologist never mentioned nitrates. I only found out after my heart surgery when I asked my cardiologist.â - u/AnginaWarrior
A 2021 survey of over 1,200 men with heart disease found that 38% didnât know about the interaction. Eleven percent admitted theyâd taken both anyway - even after being warned.
And itâs not just patients. A Medscape survey in 2022 showed only 64% of primary care doctors knew the correct waiting period between PDE5 inhibitors and nitrates. Thatâs not just a patient education problem - itâs a system failure.
What the Guidelines Say - And Why Theyâre Still Strict
The American Heart Association, the American College of Cardiology, and the FDA all say: Never combine PDE5 inhibitors with nitrates. The FDA requires a black-box warning on every PDE5 inhibitor label: âCONTRAINDICATED IN PATIENTS USING ORGANIC NITRATES IN ANY FORM.â
Separation times are non-negotiable:
- Sildenafil, vardenafil, avanafil: Wait at least 24 hours after taking the ED drug before using any nitrate.
- Tadalafil: Wait 48 hours. No exceptions.
Even if you feel fine, the drug is still in your bloodstream. The risk doesnât go away just because your erection is gone.
Electronic health records now block doctors from prescribing both at the same time. But a 2022 study in JAMA Internal Medicine found that clinicians overrode these alerts nearly 19% of the time - often because they thought the patient was âstableâ or âdidnât need to be so strict.â Thatâs how tragedies happen.
Is There Any Hope for a Safer Future?
Some recent studies are challenging the old rules. A Danish study tracking over 35,000 patients found no significant increase in heart attacks or strokes among those who took both drugs. The authors suggested the risk might be lower than we thought - especially in patients with stable heart disease.
But hereâs the problem: those studies are observational. They canât prove safety. They can only show correlation. And in medicine, when the stakes are this high - death, stroke, cardiac arrest - you donât wait for perfect data. You err on the side of caution.
The NIH is running a major clinical trial right now (NCT05211098) to finally settle this. Itâs enrolling 500 patients with stable heart disease and will monitor them closely while giving them both drugs under controlled conditions. Results are expected by the end of 2025.
In the meantime, new drugs are being developed. Mitsubishi Tanabeâs next-generation PDE5 inhibitor, MT-4567, shows 99.8% specificity for the PDE5 enzyme - meaning itâs less likely to affect other parts of the body. That could mean fewer side effects, including less risk of dangerous drops in blood pressure. But itâs still in early testing.
What You Need to Do Right Now
If youâre taking a PDE5 inhibitor:
- Check every medication youâre on - including over-the-counter, herbal, or recreational substances.
- Ask your doctor or pharmacist: âDo I take anything that contains nitrates?â
- Know the names: nitroglycerin, isosorbide dinitrate, isosorbide mononitrate, amyl nitrite (âpoppersâ).
- If youâve ever had chest pain or heart disease, assume youâre at risk - even if youâre not currently on nitrates.
- Never take a nitrate within 24 hours of sildenafil, vardenafil, or avanafil. Never within 48 hours of tadalafil.
If youâre prescribed a nitrate:
- Tell your doctor if youâre taking or thinking about taking any ED medication.
- Ask: âIs it safe for me to use an ED pill? If so, which one and when?â
- Donât assume your urologist knows your heart history - and donât assume your cardiologist knows about your ED treatment.
Communication is your best defense. Write it down. Bring a list. Ask the same question twice.
Final Warning
This isnât about being careful. Itâs about survival. One mistake - one missed conversation, one overlooked label, one âI thought it was safeâ - can kill you. There are no gray areas here. The science is clear. The guidelines are strict for a reason.
If youâre on either of these drugs, donât gamble with your life. Talk to your doctor. Get it in writing. Double-check every bottle. And if youâre ever unsure - donât take it. Wait. Call someone. Get help.
Your heart doesnât care if youâre embarrassed. It doesnât care if youâre âjust trying to feel normal again.â It only cares if youâre alive.
Can I take sildenafil and nitroglycerin if I wait 12 hours?
No. Even after 12 hours, sildenafil is still active in your system. The recommended waiting period is 24 hours after taking sildenafil before using any form of nitrate. Waiting less than that puts you at serious risk of a life-threatening drop in blood pressure.
What if I accidentally took both? What should I do?
Call emergency services immediately. Do not wait for symptoms. Symptoms like dizziness, nausea, blurred vision, fainting, or rapid heartbeat can appear within minutes. Lie down with your legs elevated to help maintain blood flow to your brain and heart. Do not drive yourself to the hospital.
Are there any ED medications that are safe with nitrates?
No. All currently approved PDE5 inhibitors - including sildenafil, tadalafil, vardenafil, and avanafil - carry the same black-box warning against nitrates. There is no safe combination. Even newer or experimental drugs have not been proven safe for concurrent use.
Do dietary nitrates (like in beets or spinach) pose a risk?
No. Dietary nitrates from food - such as beets, spinach, or celery - do not significantly raise blood nitric oxide levels to dangerous levels. The risk comes only from prescription nitrates or recreational nitrites like poppers. You can safely eat nitrate-rich foods while taking PDE5 inhibitors.
Can I use a nitrate patch or spray if I took tadalafil 36 hours ago?
No. Tadalafil stays in your system for up to 36 hours, and its effects can linger beyond that. The official guideline is to wait 48 hours after taking tadalafil before using any nitrate. Even if you feel fine, the drug is still active in your bloodstream. Do not take shortcuts.
mike tallent
November 16, 2025 AT 22:49Just saw a guy pass out at the gym last week after taking his 'little blue pill' and then using his nitro spray for 'indigestion'. He was fine, but scared the hell out of everyone. Seriously folks - if you're on ED meds, treat nitrates like a live grenade. No exceptions. đ¨đ
Jennifer Howard
November 18, 2025 AT 07:49It is utterly reprehensible that pharmaceutical companies continue to market these medications without adequately emphasizing the lethality of this interaction. The FDA's black-box warning is not a suggestion - it is a legal and ethical imperative. One must question the moral calculus of profit-driven medicine when human lives are reduced to statistical outliers.
Robert Merril
November 20, 2025 AT 01:21People still dont get it even after all these years. I had a patient take viagra and then nitroglycerin 18 hours later and ended up in the ICU. He swore his doc said 12 was fine. Docs arent always right. And patients dont read labels. Thats how you die
Noel Molina Mattinez
November 20, 2025 AT 19:33Why are we even talking about this like its a mystery. Everyone knows poppers + ED pills = bad news. Its like mixing gasoline and a lighter. If you dont know that you probably shouldnt be having sex anyway
Sylvia Clarke
November 22, 2025 AT 10:47Look I get it. Youâre trying to feel like yourself again. Youâre not a broken machine. But the fact that we still have to have this conversation in 2025 is ridiculous. Iâve seen men die because they thought âI only took it yesterdayâ or âI didnât feel anything so it must be fineâ. You donât need to feel anything for it to be killing you. This isnât about shame. Itâs about science. And science doesnât care how brave you feel. It just waits.
And yes - Iâve had patients cry because their cardiologist never mentioned it. And yes - Iâve had urologists say âoh heâs young, heâll be fineâ. No. He wonât. Not if he takes that nitro.
Itâs not just about the drugs. Itâs about the silence between doctors. The handoff that never happened. The chart that wasnât updated. The âI thought he knewâ that killed him.
So if youâre reading this - write it down. Put it on your fridge. Tell your partner. Ask your pharmacist to repeat it. Make it a ritual. Because your life isnât a footnote in a drug insert. Itâs your only one.
Kathy Grant
November 23, 2025 AT 12:13I used to think this was just a medical myth until my dad had a near-fatal episode. He took Cialis on Friday night, then used his nitro spray on Sunday morning after feeling chest pressure. He said he âfelt fineâ - until he didnât. He collapsed in the kitchen. We got him to the hospital just in time. They told us if heâd waited another 30 minutes, he wouldnât have made it.
Now I make sure every family member knows the names of these drugs. I print out the FDA warning and tape it to his medicine cabinet. I donât care if itâs awkward. Iâd rather be the annoying daughter than the one who lost him.
Itâs not about being scared. Itâs about being smart. And sometimes, smart means saying no to what feels normal.
Dave Feland
November 23, 2025 AT 16:04The real scandal here isn't the interaction - it's the fact that the FDA still allows these drugs on the market at all. The Danish study you cited? It was funded by Pfizer. The NIH trial? Designed to validate the status quo. This isn't science - it's institutional inertia dressed up as caution. The truth is, they'd rather have 100 dead men than admit they were wrong for 20 years.
Ashley Unknown
November 25, 2025 AT 15:21EVERYTHING IS A CONSPIRACY. I know a guy who took Viagra and nitroglycerin and lived - and now heâs a fitness influencer. He says the doctors are lying. He says the pharmaceutical companies are scared of natural alternatives. He says the FDA is part of a global cabal that wants to keep men weak. He says poppers are safe if youâre âin tune with your bodyâ. And guess what? Heâs still alive. So whoâs really the fool? The man who took the risk - or the people who told him not to? Iâm not saying do it. Iâm just saying⌠what if theyâre wrong?
And what about the 19% of doctors who override the alerts? Are they evil? Or are they just⌠human? What if they know something we donât? What if the real danger is the fear itself?
My therapist says I have trauma around control. Maybe this isnât about nitrates. Maybe itâs about letting go.
Roberta Colombin
November 26, 2025 AT 17:35I am a nurse in a rural clinic. Many of our patients are elderly, on fixed incomes, and see multiple doctors. One man came in with chest pain. He had taken Cialis two days ago. He said he didnât think it mattered anymore. I asked him if he knew what nitrates were. He said, âIs that the thing for heart?â I showed him the label. He started crying. He said his wife died from a heart attack and he didnât want to leave her alone. I held his hand. We called his cardiologist together. Heâs alive today because he listened. Not because he was scared. Because he was loved.
Communication is not a formality. It is an act of care.
Abdul Mubeen
November 27, 2025 AT 23:20Are we really supposed to believe this is just about medicine? Who benefits from keeping men afraid of their own sexuality? Who profits from the fear of intimacy? The pharmaceutical industry, yes - but also the medical establishment. They need you dependent. They need you confused. They need you to trust them blindly. What if the real danger isn't the drug combination - but the system that made you believe you needed it in the first place?