Tadalafil and Daridorexant: Can You Take Them Together?

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Tadalafil and Daridorexant: Understanding the Interaction

Published: 19 October 2026

If you're considering tadalafil and daridorexant together, you may be wondering whether these medicines are safe to combine. Tadalafil is a PDE5 inhibitor used to treat erectile dysfunction, while daridorexant is a newer sleeping tablet (a dual orexin receptor antagonist) prescribed for insomnia. Although no major direct interaction between tadalafil and daridorexant is commonly reported in UK prescribing guidance, both medicines can affect blood pressure and alertness, so your prescriber will carefully review your full medication list and health history during your consultation.

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) [4]. It works by relaxing the smooth muscle in the blood vessels of the penis, which increases blood flow and helps you get and maintain an erection when you are sexually aroused [1]. Tadalafil does not work without sexual stimulation.

Tadalafil is available in two main dosing schedules: on-demand tablets (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 longer duration of action is why tadalafil is sometimes called the 'weekend pill'. At Cured Pharmacy, tadalafil is available on prescription after an online consultation reviewed by a UK prescriber.

Common side effects of tadalafil include headache, indigestion, back pain, muscle aches, flushing, and nasal congestion [4]. These are usually mild and temporary. Tadalafil can also lower blood pressure slightly, which is why it must not be taken with certain other medicines (such as nitrates) and why your prescriber checks your cardiovascular health and current medications before prescribing.

What is daridorexant and how does it work?

Daridorexant (brand name Quviviq) is a dual orexin receptor antagonist licensed in the UK for the treatment of insomnia characterised by difficulty falling asleep or staying asleep [12]. Orexins are chemicals in the brain that promote wakefulness; by blocking their receptors, daridorexant helps you fall asleep and stay asleep without the same risk of dependence seen with older sleeping tablets such as benzodiazepines.

Daridorexant is usually taken as a 50 mg tablet once nightly, within 30 minutes of going to bed, and only when you can stay in bed for at least seven hours [12]. It is a prescription-only medicine and is not suitable for everyone—your doctor will check whether it is appropriate for you based on your sleep problems, other health conditions, and current medicines.

Side effects of daridorexant can include drowsiness the next day, headache, and dizziness [12]. Because it affects alertness, you should not drive or operate machinery until you know how daridorexant affects you. Daridorexant is metabolised in the liver by enzymes including CYP3A4, so medicines that affect this enzyme can alter daridorexant levels in your body.

Do tadalafil and daridorexant interact with each other?

There is no well-documented major direct interaction between tadalafil and daridorexant in current UK prescribing guidance [4][12]. Neither medicine is listed as a contraindication for the other, and they work through different mechanisms in different parts of the body—tadalafil primarily affects blood vessels in the penis, while daridorexant acts on orexin receptors in the brain to regulate sleep.

However, both medicines can have effects that may add together in some people. Tadalafil can cause a small drop in blood pressure and occasionally dizziness, particularly when you first start taking it or if you also take other blood-pressure-lowering medicines [4]. Daridorexant can cause drowsiness and dizziness, especially the morning after taking it [12]. If you experience dizziness from both medicines, this could increase your risk of falls or accidents.

Additionally, daridorexant is partly metabolised by the liver enzyme CYP3A4 [12]. Tadalafil is also metabolised by CYP3A4, but tadalafil itself is not a strong inhibitor or inducer of this enzyme, so it is unlikely to significantly alter daridorexant levels [4]. Your prescriber or pharmacist will review your full medication list during your consultation to check for any other medicines that might interact with either tadalafil or daridorexant, and they will advise you on the safest way to take both if they are prescribed together.

What your prescriber checks before prescribing tadalafil and daridorexant together

When you request tadalafil through Cured Pharmacy's online consultation, the UK prescriber will ask about all your current medicines, including any sleeping tablets such as daridorexant. They will check your cardiovascular health (including blood pressure and any history of heart disease), whether you take any medicines that are contraindicated with tadalafil (such as nitrates, nicorandil, or riociguat), and whether you have any conditions that make sexual activity inadvisable [2][4].

If you are already taking daridorexant, the prescriber will consider whether the combination is appropriate for you, taking into account any side effects you have experienced (such as dizziness or next-day drowsiness) and your overall health. They may advise starting tadalafil at a lower dose or timing the medicines carefully—for example, taking daridorexant at night and tadalafil earlier in the day if you are using the on-demand dose. Always be honest and complete in your consultation answers, as this ensures you receive safe, personalised advice.

Practical advice for taking tadalafil and daridorexant safely

If your prescriber approves the use of tadalafil and daridorexant together, follow their instructions carefully. Take daridorexant at night, within 30 minutes of going to bed, and only when you can stay in bed for at least seven hours [12]. If you are using on-demand tadalafil (10 mg or 20 mg), take it at least 30 minutes before planned sexual activity, which would typically be earlier in the day or evening, well before your bedtime dose of daridorexant [4].

Be aware of how each medicine affects you individually before combining them. If daridorexant makes you feel drowsy or dizzy the next morning, avoid driving or operating machinery until you feel fully alert. If tadalafil causes dizziness or light-headedness (especially when standing up), sit or lie down until the feeling passes, and avoid sudden changes in posture. Do not drink large amounts of alcohol, as this can worsen dizziness, lower blood pressure further, and make erectile dysfunction worse [1][4].

Keep both medicines in their original packaging, out of reach of children, and store at room temperature. Do not share your medicines with anyone else. If you experience any unexpected or troublesome side effects, contact your prescriber or pharmacist for advice. Never stop or change the dose of a prescribed medicine without professional guidance.

Timing your doses: on-demand versus daily tadalafil

If you take tadalafil on-demand (10 mg or 20 mg), you have flexibility in timing—you can take it at least 30 minutes before sexual activity, and its effects can last up to 36 hours [4]. This means you could take tadalafil in the morning or afternoon and still benefit later, without it coinciding with your evening dose of daridorexant.

If you take daily tadalafil (2.5 mg or 5 mg once a day), you can choose a time that suits your routine—many people take it in the morning [4]. This spacing may help minimise any additive effects on blood pressure or dizziness when combined with daridorexant at night. Discuss the best schedule with your prescriber during your consultation.

Medicines that must not be taken with tadalafil

Regardless of whether you take daridorexant, there are some medicines you must never take with tadalafil because the combination can cause a dangerous drop in blood pressure. Do not take tadalafil if you use nitrates (such as glyceryl trinitrate spray, isosorbide mononitrate, or isosorbide dinitrate for angina), nicorandil (another angina medicine), riociguat (for pulmonary hypertension), or amyl/alkyl nitrites (recreational drugs known as 'poppers') [4]. Do not take tadalafil together with another PDE5 inhibitor (such as sildenafil, vardenafil, or avanafil) on the same day.

If you take alpha-blockers for an enlarged prostate or high blood pressure (such as doxazosin, tamsulosin, alfuzosin, terazosin, prazosin, silodosin, or indoramin), there is a risk of low blood pressure and dizziness when combined with tadalafil [4]. You should be stable on the alpha-blocker before starting tadalafil, and your prescriber will usually recommend starting with the lowest dose of tadalafil. Always declare all your medicines during your consultation.

Potent CYP3A4 inhibitors—such as ritonavir, cobicistat (found in some HIV medicines), Paxlovid (for COVID-19), ketoconazole, itraconazole (antifungal medicines), and clarithromycin (an antibiotic)—can raise tadalafil levels in your blood [4]. Your prescriber will adjust your tadalafil dose or advise you to avoid it temporarily if you are taking one of these medicines. CYP3A4 inducers (such as rifampicin, carbamazepine, phenytoin, and St John's wort) can make tadalafil less effective [4].

When to seek urgent medical help with tadalafil and daridorexant

Seek urgent medical help (call 999 or go to A&E) if you experience an erection that lasts longer than four hours (priapism), even if it is not painful [4]. Priapism is a medical emergency that requires immediate treatment to prevent permanent damage to the penis. Also seek urgent help if you have sudden loss of vision in one or both eyes (which could be a sign of non-arteritic anterior ischaemic optic neuropathy, or NAION) or sudden decrease or loss of hearing, sometimes with ringing in the ears or dizziness [4].

If you develop chest pain during or after sexual activity, do not take more tadalafil and do not use nitrate medicines (such as GTN spray) without medical advice, as the combination can be dangerous [4]. Sit or lie down, and call 999 if the chest pain is severe, does not go away, or is accompanied by shortness of breath, nausea, or pain spreading to your arm, jaw, or back.

If you experience severe dizziness, fainting, or a very fast or irregular heartbeat after taking tadalafil and daridorexant together, seek same-day medical advice from your GP or call NHS 111. These symptoms could indicate a significant drop in blood pressure or another cardiovascular problem that needs assessment. Always keep your prescriber or pharmacist informed of any new or worsening symptoms.

Side effects to monitor when taking both medicines

Common side effects of tadalafil include headache, indigestion, back pain, muscle aches, flushing, and nasal congestion [4]. Common side effects of daridorexant include next-day drowsiness, headache, and dizziness [12]. If you notice these side effects are more troublesome when taking both medicines together, contact your prescriber for advice—they may adjust your doses or suggest a different treatment.

Report any unusual symptoms, such as severe or persistent headache, unexplained bruising or bleeding, swelling of the face or throat, difficulty breathing, or a rash, to your GP or pharmacist promptly. These could be signs of a more serious reaction that needs medical attention.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 19 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 19 October 2026]
3. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 19 October 2026]
4. Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 19 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.