Vardenafil and Isosorbide mononitrate: What Should Your Pharmacist Check?

Short answer: vardenafil (Levitra, Staxyn and generics) and isosorbide mononitrate (Imdur, Monoket, Ismo and generics) should not be taken together. Both drugs widen blood vessels through the same chemical pathway, and the combination can push blood pressure down far enough to cause fainting, a heart attack or collapse. If you have been prescribed isosorbide mononitrate for angina and you are also dealing with erectile dysfunction, the right move is a conversation with your pharmacist and cardiologist, not a workaround.

This guide is written for the person standing at the pharmacy counter with two prescriptions, or the partner trying to make sense of a warning label. It walks through the exact checks a careful pharmacist runs when vardenafil and isosorbide mononitrate show up on the same profile, what each check is looking for, and what you can do next if the answer is “not together.”

Quick fact	What it means for you
Interaction level	Contraindicated (do not combine)
Main danger	Severe, sudden drop in blood pressure
Is there a “safe gap” between doses?	No. Isosorbide mononitrate is taken every day, so there is no window
Can you skip your nitrate to take vardenafil?	No. Stopping a nitrate can trigger angina
Who to talk to	Your pharmacist first, then your cardiologist or GP

Why This Pairing Comes Up So Often

It is not a coincidence that many men taking a heart medicine also need help with erections. Erectile dysfunction and coronary artery disease share the same roots: narrowed, stiffened blood vessels, high blood pressure, diabetes, high cholesterol, smoking and age. The arteries that supply the penis are smaller than the coronary arteries, so erection problems can show up years before chest pain does. By the time someone is prescribed a daily nitrate for angina, ED is often already part of the picture.

That overlap is exactly why pharmacists are trained to flag this combination quickly. A man might get isosorbide mononitrate from a cardiologist, then get vardenafil from a different doctor, an online clinic, or a friend. Without one person looking at the full medicine list, the clash can slip through.

How Each Medicine Works (In Plain Language)

Isosorbide mononitrate

Isosorbide mononitrate is a long-acting organic nitrate. Inside the body it releases nitric oxide, a gas that tells the smooth muscle in blood vessel walls to relax. Relaxed veins hold more blood, so the heart has less to pump and needs less oxygen. That is how it prevents angina attacks. It is usually taken once a day as an extended-release tablet, or twice a day at uneven times as an immediate-release tablet, so that the body gets a short “nitrate-free” period each day and the drug keeps working.

Vardenafil

Vardenafil is a phosphodiesterase type 5 (PDE5) inhibitor. When you are sexually aroused, nerves release nitric oxide in the penis, which raises a messenger called cyclic GMP (cGMP). cGMP relaxes the blood vessels and lets blood flow in. The PDE5 enzyme normally breaks down cGMP; vardenafil blocks that enzyme so cGMP lasts longer and the erection is easier to get and keep. If you would like a broader comparison of vardenafil against other ED drugs, see our guide on vardenafil vs sildenafil.

Where they collide

One drug floods the system with nitric oxide. The other stops cGMP being broken down. Together they produce far more vessel relaxation than either drug alone, and not just in the penis: throughout the body. The result is a fall in blood pressure that can be large, fast and hard to reverse. The official vardenafil prescribing information states that concomitant use with nitrates and nitric oxide donors in any form is contraindicated (vardenafil prescribing label). UK product information for isosorbide mononitrate carries the matching warning from the other side.

The Pharmacist’s Checklist: 8 Things That Should Be Checked

When both medicines appear on a profile, or when a patient asks about adding vardenafil, here is what a thorough pharmacist works through. Knowing the list helps you answer quickly and spot anything that has been missed.

1. Confirm the nitrate really is isosorbide mononitrate (and the strength)

The first job is identification. Isosorbide mononitrate comes under several brand names and in immediate-release and extended-release forms, commonly 10 mg to 120 mg. A pharmacist will confirm the exact product because the dosing schedule tells them how continuously you are exposed to nitrate. For an extended-release tablet taken each morning, nitrate effect covers most of the day, every day. That rules out the idea of “timing around it.”

2. Look for other nitrates and nitric oxide donors

People on isosorbide mononitrate often carry a second nitrate for breakthrough chest pain, such as a glyceryl trinitrate (nitroglycerin) spray or under-the-tongue tablet. Others use nitrate patches or ointment. In some countries, nicorandil (which has a nitrate component) is used for angina. Recreational “poppers” (amyl or alkyl nitrites) belong to the same danger group. A pharmacist will ask about all of these, because any one of them is enough to make vardenafil unsafe. For a related explainer, see our post on avanafil and nitroglycerin, which covers the rescue-spray problem in detail.

3. Check whether the nitrate is still needed (and who decides)

Sometimes a nitrate was started years ago and nobody has reviewed it since a stent or bypass operation. A pharmacist cannot stop it, but they can flag it for the cardiologist. If a specialist decides the nitrate is no longer required and stops it safely, the ED question can be revisited later. What a pharmacist will never advise is skipping or stopping isosorbide mononitrate on your own to make room for vardenafil. UK product information specifically warns that nitrate therapy should not be interrupted to take a PDE5 inhibitor because doing so can provoke an angina attack.

4. Check the source of the vardenafil

Was vardenafil prescribed by a doctor who knows about the nitrate? Bought online? Given by a friend? A surprising number of ED tablets are obtained outside normal prescribing, which is exactly when dangerous combinations slip through. A pharmacist will also gently check whether the product is genuine, because counterfeit ED pills may contain unknown amounts of a different PDE5 drug. Our guide on how to spot fake ED products explains the warning signs.

5. Review other blood pressure–lowering medicines

Even outside the nitrate problem, a heart patient’s list usually contains several drugs that lower blood pressure: beta-blockers, calcium channel blockers, ACE inhibitors, diuretics. Alpha-blockers for the prostate (such as tamsulosin) add another layer. The pharmacist checks the total “blood-pressure load,” because it matters for any future ED plan once the nitrate issue is settled. You can read more in our article on which blood pressure medications cause erectile dysfunction.

6. Screen for drugs that raise vardenafil levels

Vardenafil is broken down mainly by the liver enzyme CYP3A4. Strong blockers of that enzyme, such as ritonavir, ketoconazole, itraconazole and clarithromycin, can multiply vardenafil levels and its blood-pressure effect. Grapefruit juice can also raise levels. These checks matter for any patient, but they become critical when the heart is already under strain.

7. Check heart rhythm medicines and QT risk

Vardenafil can slightly lengthen the QT interval on an ECG. Labels advise avoiding it in people with congenital long QT and in those taking certain antiarrhythmics (class IA such as quinidine and procainamide, or class III such as amiodarone and sotalol). Many angina patients also have rhythm problems, so a pharmacist cross-checks this list too.

8. Document the decision and tell you what to say in an emergency

The last check is communication. A good pharmacist records the interaction alert, explains it to you in plain words, and makes sure you know to tell paramedics or emergency staff if you have taken any PDE5 inhibitor. That single sentence can change how chest pain is treated in an emergency.

What “Contraindicated” Actually Means Here

Drug interactions are graded. Some mean “watch closely,” some mean “adjust the dose.” Contraindicated means the risk is judged to outweigh any benefit, so the two should not be used together at all. Interaction checkers such as Drugs.com’s isosorbide mononitrate and vardenafil report list the pair as not recommended because of the risk of an excessive blood pressure drop and cardiovascular collapse.

There is no lower dose of vardenafil that makes this pairing acceptable. Even the 5 mg starting dose still blocks PDE5, and the effect of a nitrate is not reduced by spacing tablets apart when the nitrate is taken daily. That is the key difference between a daily nitrate and an occasional rescue spray: with a daily long-acting nitrate, there is simply no gap to plan around.

What Would Happen in the Body

It helps to picture the sequence, because recognising early symptoms can save precious minutes.

Vessels relax body-wide. Veins in the legs and abdomen widen and pool blood.
Less blood returns to the heart. The heart has less to pump out with each beat.
Blood pressure falls. The person may feel light-headed, flushed, sweaty, nauseous or have a pounding headache.
The heart speeds up to compensate. In someone with narrowed coronary arteries, a faster heart needs more oxygen, which can trigger chest pain.
Brain and heart are under-supplied. Fainting, confusion, a heart attack or stroke can follow if pressure keeps dropping.

Sexual activity itself raises heart workload, which makes the situation riskier still if it happens during intercourse.

If You Have Already Taken Both: Do This Now

If you realise you have taken vardenafil while on isosorbide mononitrate, do not wait to see what happens.

Lie down with your legs raised if you feel dizzy, weak or faint. Do not stand up suddenly.
Call emergency services if you have chest pain, fainting, severe dizziness, confusion, shortness of breath or a racing heart.
Tell the responders exactly what you took and when: the name, the dose and the time of the vardenafil, and your nitrate dose.
Do not use your nitroglycerin spray or tablets for chest pain without telling the emergency team that you have taken vardenafil.
Do not take more of either drug until a doctor has reviewed you.

If you feel completely well, still phone your pharmacist, an out-of-hours service or your doctor for advice. Interaction effects can build over the following hours.

How Long Does Vardenafil Stay a Problem?

Vardenafil has a half-life of roughly four to five hours, meaning half of a dose has cleared after that time. But “half gone” is not “gone.” Prescribing information notes that a safe interval between a vardenafil dose and later nitrate use has not been formally established. In a study with nitroglycerin, extra blood pressure and heart rate changes were no longer detected when vardenafil 20 mg was taken 24 hours earlier, and many emergency teams use 24 hours as a working minimum. That figure is relevant to emergency doctors deciding whether nitrates can be given after accidental exposure; it is not permission to alternate the two at home.

Safer Paths Forward for ED When You Take Isosorbide Mononitrate

Being told “not this pill” does not mean “no treatment.” Here are routes your doctor can discuss.

Treat the underlying heart and vessel risk

Better blood pressure control, stopping smoking, regular walking, weight loss and good diabetes control improve blood flow everywhere, including to the penis. Supervised exercise or pelvic floor physical therapy for erectile dysfunction can help some men noticeably.

Review whether the nitrate can be changed

In some patients, a cardiologist may decide angina can be controlled with other drugs (for example a beta-blocker, a calcium channel blocker or ranolazine, where appropriate), allowing the nitrate to be withdrawn safely under supervision. This is a specialist decision and is not suitable for everyone, especially people with frequent angina.

Non-tablet ED treatments

Vacuum erection devices: a cylinder and pump draw blood into the penis, and a ring holds it there. No interaction with nitrates.
Alprostadil: given as an injection into the penis or a small pellet in the urethra. It works locally, though your doctor will still check your heart health.
Penile implants: a surgical option for men who do not respond to other treatment.

Address psychological factors

Fear of chest pain during sex can itself cause erection problems. Cardiac rehabilitation teams often address sexual activity openly, and counselling can help. Our article on how to beat psychological erectile dysfunction covers practical steps.

What About Other ED Pills: Are Any Safe With Nitrates?

No. Every PDE5 inhibitor shares this interaction: sildenafil (Viagra), tadalafil (Cialis), avanafil (Stendra/Spedra) and vardenafil. Tadalafil is actually the longest-lasting, which makes it even less forgiving. Switching brands does not solve the problem. We cover the avanafil version of this same question in avanafil and isosorbide mononitrate, and the related dinitrate question in vardenafil and isosorbide dinitrate.

Be equally careful with “natural” or “herbal” sex pills sold online. Regulators repeatedly find hidden sildenafil, tadalafil or analogues in these products, so a “herbal” label offers no protection against the nitrate interaction.

A Simple Script for the Pharmacy Counter

Many men find this topic awkward to raise. You can keep it short. Try something like:

“I take isosorbide mononitrate for angina every day. I’ve been having erection problems and I’ve been offered vardenafil. Can you check whether that’s safe, and if not, what I should ask my doctor about instead?”

Bring a full list of what you take, including sprays, patches, supplements and anything bought online. Pharmacists hear these questions every day, and most pharmacies have a private consultation room if you would rather not talk at the counter.

Questions to Ask Your Pharmacist

Is every medicine I take that counts as a nitrate or nitric oxide donor on my record?
Are any of my other medicines likely to lower my blood pressure further?
If my cardiologist ever stops my nitrate, how long should I wait before an ED medicine could be considered?
What should I tell paramedics if I have chest pain and have taken an ED drug?
Which non-tablet ED options would be safe with my heart condition?
Is the ED product I bought online genuine, and what is actually in it?

Special Situations Pharmacists Watch For

Men who use their nitrate “only sometimes”

Some people take isosorbide mononitrate irregularly despite being prescribed it daily, and assume that makes vardenafil acceptable on “off” days. It does not. Irregular nitrate use is still nitrate use, and unpredictable angina is precisely the situation in which a nitrate may be needed urgently. A pharmacist will flag irregular use to your doctor because it also suggests your angina plan may need review.

Older men

For men aged 65 and over, vardenafil labels already suggest starting at 5 mg because the drug clears more slowly. That precaution does not change the nitrate rule; it simply shows how sensitive blood pressure can be with age.

Men with kidney or liver problems

Both conditions can raise vardenafil levels. Combined with heart disease and nitrates, the risks stack up, and a pharmacist will mention this to the prescriber.

Buying Vardenafil Online or Abroad: Extra Checks

Online clinics and overseas pharmacies have made ED tablets easier to get, which is helpful for many men but creates a gap for heart patients. A short online questionnaire may ask “Do you take nitrates?” without explaining that isosorbide mononitrate is a nitrate. If the brand on your box says Imdur, Monoket, Elantan or Isotard, you might honestly tick “no.”

Before ordering, check these points:

Read the active ingredient, not the brand. Anything containing “nitrate” or “nitrite” in the ingredient name is relevant.
Answer health questionnaires in full. List your angina diagnosis even if the form does not ask directly.
Use a regulated pharmacy. In the UK, look for the GPhC registration; in the US, check state board licensing. Unregulated sites may not ask any questions at all.
Keep one pharmacy record. If you use an online service, tell your regular pharmacist too, so your full list sits in one place.
Be wary of “generic Levitra” from unknown makers. Strength and purity cannot be verified, and the product may contain a different PDE5 drug altogether.

If you are unsure whether a product is genuine or which drug it really contains, bring it to your pharmacist before taking it. They can identify most licensed tablets from markings and packaging.

Frequently Asked Questions

Can I take vardenafil 24 hours after my isosorbide mononitrate tablet?

No. Because isosorbide mononitrate is taken every day and gives continuous nitrate exposure, there is no point in the day when vardenafil would be safe. The 24-hour figure you may have read relates to how long emergency doctors may wait before giving a nitrate after someone has taken a PDE5 inhibitor, not to routine combined use.

What if my doctor prescribed both?

Ask your pharmacist to contact the prescriber before you take either together. Sometimes the prescriber was not aware of the other medicine. This is a known safety check, and pharmacists are expected to raise it.

Is a lower dose of vardenafil, like 5 mg, safe with isosorbide mononitrate?

No. The interaction is a contraindication, not a dose adjustment. There is no established safe dose of vardenafil alongside nitrates.

Can I stop my isosorbide mononitrate for a weekend?

Please do not. Stopping a nitrate abruptly can bring on angina, and vardenafil would still be risky if any nitrate remained in your system. Any change to your angina treatment needs your cardiologist.

Does the orally dissolving form of vardenafil (Staxyn) behave differently?

The orally dissolving tablet delivers vardenafil differently, but it is still a PDE5 inhibitor, and the nitrate contraindication is the same. Our comparison of Levitra vs Staxyn explains the two formulations.

Are there ED options that are definitely safe with nitrates?

Vacuum erection devices do not interact with nitrates. Other options, such as alprostadil or surgery, need a personal discussion with your doctor about your heart health and overall fitness for sexual activity.

Is sex itself safe if I have angina?

For many people with stable angina, yes, but this depends on how well controlled your symptoms are and your exercise tolerance. Ask your cardiologist directly. Cardiac rehabilitation services can give personalised guidance.

The Bottom Line

Vardenafil and isosorbide mononitrate do not mix. The two act on the same nitric oxide and cGMP pathway, and together they can drop blood pressure to dangerous levels. Because isosorbide mononitrate is a daily, long-acting nitrate, there is no timing trick that makes the combination safe. Your pharmacist’s job is to catch the clash, check for other hidden nitrates and blood-pressure lowering drugs, verify where the ED medicine came from, and point you toward options that protect both your heart and your sex life. Your job is to bring the full list, ask the question out loud, and never pause your nitrate on your own.

Related Guides on Pinkviva

References and Further Reading

Medical disclaimer: This article is for general education and does not replace advice from your doctor, cardiologist or pharmacist. Never start, stop or change a heart medicine without professional guidance. If you have chest pain, fainting or severe dizziness, call emergency services immediately.