Tadalafil and Quinapril: Can You Take Them Together?

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Tadalafil and Quinapril: Understanding the Interaction

Published: 25 October 2026

Many men taking tadalafil and quinapril together want to know whether this combination is safe. Tadalafil (the active ingredient in Cialis) is a medicine used to treat erectile dysfunction, while quinapril is an ACE inhibitor prescribed to lower blood pressure and protect the heart. The good news is that these two medicines can usually be taken together, but because both can lower blood pressure, your prescriber will need to check your individual circumstances carefully to ensure the combination is safe for you [1][2].

What is tadalafil and how does it work?

Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction (ED). It works by relaxing the blood vessels in the penis, allowing increased blood flow when you are sexually aroused. This helps you achieve and maintain an erection suitable for sexual activity [4].

Tadalafil is available in two forms: on-demand tablets (usually 10mg or 20mg) taken at least 30 minutes before sex, with effects lasting up to 36 hours; and daily tablets (2.5mg or 5mg) taken once a day, allowing for spontaneity. Unlike some ED medicines, tadalafil does not cause an erection on its own—you still need sexual stimulation for it to work [4].

Because tadalafil relaxes blood vessels throughout the body, not just in the penis, it can also lower your blood pressure slightly. This is usually mild and well-tolerated, but it becomes important when you are taking other medicines that also affect blood pressure, such as quinapril [2][4].

What is quinapril and why is it prescribed?

Quinapril belongs to a group of medicines called ACE inhibitors (angiotensin-converting enzyme inhibitors). It is commonly prescribed to treat high blood pressure (hypertension) and to protect the heart and kidneys in people with heart failure or after a heart attack. Quinapril works by blocking an enzyme that produces a substance which narrows blood vessels, so your blood vessels relax and widen, reducing blood pressure [2].

Many men with erectile dysfunction also have high blood pressure or other cardiovascular conditions, so it is quite common to be prescribed both an ACE inhibitor like quinapril and an ED treatment like tadalafil. In fact, treating high blood pressure and other heart-related conditions can sometimes improve erectile function over time [1][2].

Quinapril is usually taken once or twice a day, and it is important to take it regularly as prescribed, even if you feel well. Do not stop taking quinapril or change your dose without speaking to your doctor, as this could affect your blood pressure control and overall health.

How do tadalafil and quinapril interact with each other?

When you take tadalafil and quinapril together, both medicines can lower your blood pressure. Tadalafil does this by relaxing blood vessels (including those in the penis), while quinapril does it by preventing blood vessels from narrowing. The combined effect means your blood pressure may drop a little more than it would with either medicine alone [2][4].

For most men, this interaction is mild and manageable. However, in some people, the combination can cause symptoms of low blood pressure, such as dizziness, light-headedness (especially when standing up quickly), or feeling faint. These symptoms are usually temporary and often settle as your body adjusts to the medicines [4].

It is important to understand that this interaction is not the same as the dangerous interaction between tadalafil and nitrate medicines (such as GTN spray or isosorbide mononitrate). Nitrates and PDE5 inhibitors must never be taken together because they can cause a severe, potentially life-threatening drop in blood pressure. Quinapril is not a nitrate, so the combination with tadalafil is usually safe when prescribed and monitored appropriately [2][4].

The mechanism in plain English

Think of your blood vessels as flexible tubes. Quinapril keeps these tubes relaxed and open by blocking a chemical that would normally make them tighten. Tadalafil also relaxes the tubes, particularly in the penis, by blocking a different enzyme. When both medicines are working at the same time, the tubes stay more relaxed, which can lower the pressure of blood flowing through them. This is usually helpful for your heart and circulation, but if the pressure drops too much, you might feel dizzy or faint. Your prescriber will check that your blood pressure is stable and that you can tolerate both medicines together safely.

What does your prescriber check before prescribing tadalafil with quinapril?

Before prescribing tadalafil to someone taking quinapril, a UK prescriber will review your full medical history and current medicines. They will check your blood pressure readings to ensure they are stable and not too low, as starting tadalafil when your blood pressure is already low can increase the risk of dizziness or fainting [2][4].

Your prescriber will also ask about any symptoms you have experienced, such as dizziness when standing up, chest pain, or shortness of breath. They will want to know whether you have any heart conditions, such as angina, recent heart attack, or heart failure, because these can affect whether tadalafil is suitable for you. Sexual activity itself puts extra strain on the heart, so your prescriber needs to confirm that you are well enough for sex [1][2].

If you are taking other medicines in addition to quinapril—such as other blood pressure tablets, diuretics (water tablets), or medicines for diabetes—your prescriber will consider how these might interact with tadalafil. They may recommend starting with a lower dose of tadalafil (such as 10mg rather than 20mg) to minimise the risk of side effects. It is essential to declare all your current medicines, including over-the-counter products and herbal supplements, during your consultation [4].

Starting on the right dose

For men taking quinapril or other blood pressure medicines, the usual starting dose of tadalafil is 10mg taken on-demand, at least 30 minutes before sexual activity. If this is well-tolerated and effective, the dose may be increased to 20mg, or reduced to 5mg if side effects occur. Some men prefer daily tadalafil (2.5mg or 5mg once a day), which allows for more spontaneity. Your prescriber will discuss which option suits your lifestyle and medical needs best [4].

Practical advice for taking tadalafil and quinapril safely together

If you have been prescribed tadalafil while taking quinapril, there are some simple steps you can take to use both medicines safely. First, take your medicines exactly as prescribed—do not take more tadalafil than recommended, and do not skip doses of quinapril. Tadalafil should be taken no more than once a day if you are using the on-demand tablets [4].

Be cautious when standing up quickly, especially in the first few hours after taking tadalafil, as this is when dizziness is most likely to occur. Sit on the edge of the bed for a moment before standing, and rise slowly from a sitting or lying position. Avoid drinking large amounts of alcohol when taking tadalafil, as alcohol can also lower blood pressure and make dizziness worse. Heavy drinking can also make erectile dysfunction worse and reduce the effectiveness of tadalafil [2][4].

If you experience persistent dizziness, light-headedness, or feel faint after taking tadalafil, sit or lie down until the symptoms pass, and contact your GP or pharmacist for advice. Do not drive or operate machinery if you feel dizzy. If you develop chest pain during or after sexual activity, stop and seek urgent medical help—do not take any nitrate medicine (such as GTN spray) if you have used tadalafil in the past 48 hours, as this combination is dangerous [4].

Warning signs and when to seek help with tadalafil and quinapril

Most men taking tadalafil and quinapril together tolerate the combination well, but it is important to know the warning signs that need medical attention. Seek urgent help (call 999 or go to A&E) if you experience chest pain during or after sex, sudden loss of vision in one or both eyes, sudden decrease or loss of hearing, or an erection that lasts longer than four hours (priapism). These are rare but serious side effects that require immediate treatment [4].

Contact your GP or pharmacist the same day if you experience severe or persistent dizziness, fainting, or a very fast or irregular heartbeat. These could be signs that your blood pressure has dropped too low or that the combination of medicines is not suitable for you. Your doctor may need to adjust your doses or review your treatment [2][4].

If you are prescribed a new medicine by another doctor or buy an over-the-counter product, always check with your pharmacist whether it is safe to take with tadalafil and quinapril. Some medicines, such as potent antifungals (ketoconazole, itraconazole) or certain antibiotics (clarithromycin), can increase tadalafil levels in your blood and raise the risk of side effects. Never take tadalafil with nitrate medicines, nicorandil, riociguat, or recreational drugs called 'poppers', as these combinations can cause a dangerous drop in blood pressure [4].

Keeping your prescriber informed

Always inform your prescriber if your health changes—for example, if you develop new symptoms, are admitted to hospital, or are started on a new medicine by another doctor. If you are due to have surgery, tell the anaesthetist and surgeon that you take tadalafil and quinapril. Keeping your prescriber up to date ensures that your treatment remains safe and effective.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 25 October 2026]
2. National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 25 October 2026]
3. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 25 October 2026]

Information on this page is for educational purposes only and is not medical advice. Prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting or changing any medication.