Tadalafil and Aliskiren: Can You Take Them Together?

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Key takeaways

• No major direct interaction exists between tadalafil and aliskiren, but both can lower blood pressure
• Your prescriber will check your blood pressure control before approving tadalafil
• Starting on a lower dose of tadalafil may reduce the risk of dizziness
• Always declare all your medicines during your online consultation for a safe assessment
• Never take tadalafil with nitrates, nicorandil, or riociguat—this combination is dangerous

What is tadalafil and how does it work?

Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in men [3][4]. It belongs to a group of medicines called phosphodiesterase type 5 (PDE5) inhibitors, which work by relaxing the blood vessels in the penis, allowing more blood to flow in when you are sexually aroused. Tadalafil does not cause an erection on its own—sexual stimulation is still needed for it to work [4].

Tadalafil is available in two forms: on-demand tablets (usually 10 mg or 20 mg taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours) and daily low-dose tablets (2.5 mg or 5 mg taken once a day) [4]. The branded version is known as Cialis, but generic tadalafil is widely available and works in exactly the same way. Because tadalafil relaxes blood vessels throughout the body, it can also cause a small drop in blood pressure, which is why interactions with other blood-pressure-lowering medicines need careful assessment [4].

What is aliskiren and why is it prescribed?

Aliskiren is a prescription medicine used to treat high blood pressure (hypertension). It belongs to a class of drugs called direct renin inhibitors, which work by blocking renin, an enzyme involved in the production of a hormone that narrows blood vessels. By blocking renin, aliskiren helps blood vessels relax and widen, which lowers blood pressure and reduces the strain on your heart.

Aliskiren is usually prescribed when other blood pressure medicines have not been fully effective or are not suitable. It may be used alone or in combination with other antihypertensive drugs. Like all blood-pressure-lowering medicines, aliskiren can cause dizziness or light-headedness, especially when you first start taking it or if the dose is increased. Because it lowers blood pressure, any additional medicine that also affects blood pressure—such as tadalafil—requires careful consideration by your prescriber.

How aliskiren lowers blood pressure

Aliskiren works at the very start of the renin-angiotensin-aldosterone system (RAAS), a hormone pathway that regulates blood pressure and fluid balance. By inhibiting renin, aliskiren reduces the production of angiotensin II, a powerful substance that constricts blood vessels and raises blood pressure. This mechanism is different from other common blood pressure medicines such as ACE inhibitors or angiotensin receptor blockers (ARBs), which act further down the same pathway. Understanding how aliskiren works helps explain why your prescriber will assess the overall effect on your blood pressure when adding tadalafil.

At a glance

Can you take tadalafil and aliskiren together?

There is no major direct drug interaction between tadalafil and aliskiren that would make the combination unsafe or contraindicated. However, both medicines can lower blood pressure, so taking them together may add to this blood-pressure-lowering effect. For most men whose blood pressure is well controlled on aliskiren, this additive effect is usually manageable and does not cause problems, but it does mean your prescriber must check your current blood pressure, cardiovascular health, and any other medicines you are taking before prescribing tadalafil [3][4].

During your online consultation at Cured Pharmacy, you will be asked about all your current medicines, including aliskiren, and your blood pressure readings. The prescriber will assess whether tadalafil is suitable for you and may recommend starting on a lower dose to minimise the risk of dizziness or light-headedness. It is important to be honest and complete in your answers, as this ensures the safest and most effective treatment. If your blood pressure is not well controlled, or if you have other cardiovascular risk factors, your prescriber may advise seeing your GP for a review before starting ED treatment [2].

How the interaction between tadalafil and aliskiren works

Both tadalafil and aliskiren can cause blood vessels to relax and widen, which lowers blood pressure. Tadalafil does this by increasing levels of a substance called cyclic GMP in the smooth muscle of blood vessels, while aliskiren reduces the production of angiotensin II, a hormone that constricts blood vessels. When taken together, these two mechanisms can add up, potentially causing a greater drop in blood pressure than either medicine alone [4].

For most men, this additive effect is mild and does not cause symptoms. However, some people may experience dizziness, light-headedness, or even fainting, especially when standing up quickly. This is more likely if you are also taking other blood-pressure medicines, if you are dehydrated, or if you drink a lot of alcohol. The risk is also higher when you first start tadalafil or if the dose is increased. Your prescriber will take all these factors into account and may recommend starting on the lowest effective dose of tadalafil (for example, 10 mg on-demand or 2.5 mg daily) to reduce the chance of side effects [3][4].

Why blood pressure control matters

Good blood pressure control is essential for your overall health and also affects how safely you can use tadalafil. If your blood pressure is too high, it can damage your blood vessels and increase the risk of heart attack, stroke, and kidney disease. On the other hand, if your blood pressure drops too low (hypotension), you may feel dizzy, weak, or faint, and in rare cases this can be dangerous. Your prescriber will check that your blood pressure is stable and within a safe range before prescribing tadalafil, and they may ask you to monitor your blood pressure at home or see your GP for a check-up if there are any concerns [2].

What your prescriber will check before prescribing tadalafil and aliskiren

When you request tadalafil through Cured Pharmacy's online consultation, the prescriber will ask detailed questions about your medical history, current medicines, and recent blood pressure readings. They will want to know how long you have been taking aliskiren, whether your blood pressure is well controlled, and whether you have experienced any side effects such as dizziness or fainting. You will also be asked about other cardiovascular conditions, such as angina, heart failure, or a recent heart attack or stroke, as these can affect whether tadalafil is safe for you [2][3].

The prescriber will also check for any other medicines that could interact with tadalafil. For example, if you are taking nitrates (such as GTN spray or isosorbide mononitrate) for angina, or nicorandil, you must not take tadalafil, as the combination can cause a dangerous drop in blood pressure [3][4]. Alpha-blockers (such as doxazosin or tamsulosin) also require caution, and you should be stable on the alpha-blocker before starting a low dose of tadalafil. If you are taking any other blood-pressure medicines in addition to aliskiren, the prescriber will assess the overall effect on your blood pressure. Always declare every medicine you are taking, including over-the-counter products and herbal supplements, to ensure a safe assessment [2].

Practical advice for taking tadalafil and aliskiren safely

If your prescriber approves tadalafil while you are taking aliskiren, there are several practical steps you can take to use both medicines safely. First, take tadalafil exactly as prescribed—do not take more than the recommended dose or take it more often than once a day (for on-demand tablets). If you are using daily tadalafil, take it at the same time each day to maintain steady levels in your body [4]. Avoid drinking large amounts of alcohol, as this can add to the blood-pressure-lowering effect and make dizziness more likely. Heavy alcohol can also make erectile dysfunction worse [1].

Be aware of how you feel when you first start tadalafil or if your dose is increased. If you experience dizziness or light-headedness, sit or lie down until it passes, and avoid driving or operating machinery until you know how the medicine affects you. Stand up slowly from sitting or lying positions to reduce the risk of a sudden drop in blood pressure. If you feel faint, very dizzy, or unwell, stop taking tadalafil and contact your GP or pharmacist for advice. Do not stop taking aliskiren or any other prescribed medicine without speaking to your doctor first, as this could cause your blood pressure to rise [2].

Keep your GP informed that you are taking tadalafil, especially if your blood pressure control changes or if you start any new medicines. Your GP may want to check your blood pressure more regularly to ensure it remains stable. If you develop chest pain during sexual activity, stop and seek urgent medical help—do not take nitrate medicines such as GTN spray if you have used tadalafil in the past 48 hours, as this can be dangerous [3][4]. Report any sudden loss of vision or hearing, or an erection lasting more than four hours, to A&E immediately.

Monitoring and follow-up

Regular monitoring is an important part of managing both high blood pressure and erectile dysfunction. Your GP will usually review your blood pressure and aliskiren treatment at least once a year, and more often if your blood pressure is not well controlled or if you have other health conditions. If you notice any new symptoms or side effects after starting tadalafil, such as persistent dizziness, headaches, or flushing, mention these at your next review or contact your GP or pharmacist sooner. Keeping a record of your blood pressure readings at home can also be helpful and may be recommended by your healthcare team [2].

When to get urgent help

• Chest pain during or after sexual activity—do not take nitrate medicines if you have used tadalafil in the past 48 hours; call 999
• An erection lasting more than 4 hours (priapism)—go to A&E immediately to prevent permanent damage
• Sudden loss of vision in one or both eyes—stop tadalafil and seek urgent medical help
• Sudden loss of hearing or ringing in the ears—stop tadalafil and contact your GP or go to A&E
• Severe dizziness, fainting, or feeling very unwell after taking tadalafil—seek same-day medical advice from your GP or call 111

Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.