Tadalafil and Montelukast: Can You Take Them Together?

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At a glance

What is tadalafil and how does it work?

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

Tadalafil is available in two forms: on-demand tablets (10mg or 20mg) taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours, and daily tablets (2.5mg or 5mg) taken once a day at the same time [4]. The longer duration of action has earned tadalafil the nickname 'the weekend pill'. It is the generic version of the branded medicine Cialis.

At Cured Pharmacy, tadalafil is available from £7.95 after an online consultation with a UK-registered prescriber. All prescription ED treatments require a clinical assessment to ensure they are safe and appropriate for you.

What is montelukast and why is it prescribed?

Montelukast is a prescription medicine used to prevent asthma symptoms and to relieve symptoms of seasonal allergic rhinitis (hay fever). It belongs to a class of medicines called leukotriene receptor antagonists, which work by blocking the action of leukotrienes—chemicals in the body that cause inflammation, constriction of airways, and mucus production in the lungs.

Montelukast is usually taken once daily in the evening, either as a 10mg tablet for adults or as a lower-dose chewable tablet for children. It is used for long-term control of asthma and is not a rescue inhaler for sudden breathing problems. Many people take montelukast alongside other asthma medicines such as inhaled corticosteroids or bronchodilators.

Because montelukast works through a completely different mechanism to tadalafil, the two medicines do not directly interfere with each other's action in the body. However, it is still essential to tell your prescriber about all medicines you take, including montelukast, during your ED consultation.

Can you take tadalafil and montelukast together?

Yes, tadalafil and montelukast can generally be taken together. No major interaction is commonly reported between these two medicines, as they work through entirely different pathways in the body. Montelukast blocks leukotriene receptors in the airways, while tadalafil inhibits the PDE5 enzyme in blood vessels. Neither medicine is known to significantly affect the metabolism or action of the other.

That said, every person's medical situation is unique. Your prescriber will review all your current medicines, including montelukast, during your consultation to check for any individual factors that might affect your treatment. This includes considering your overall health, other conditions you may have, and any other medicines you take alongside montelukast.

It is important never to start, stop, or change the dose of any prescribed medicine—including montelukast—without speaking to your doctor or pharmacist first. If you have been prescribed montelukast for asthma or allergies, continue taking it as directed while using tadalafil, unless your healthcare professional advises otherwise.

What your prescriber checks

During your online consultation at Cured Pharmacy, you will be asked to list all medicines you currently take, including montelukast. The prescriber will check for any interactions, not just with montelukast but with every medicine on your list. They will also review your medical history, blood pressure, cardiovascular health, and any conditions that might make tadalafil unsuitable [2].

Certain medicines must never be taken with tadalafil, including nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, and recreational drugs known as 'poppers' [4]. These combinations can cause a dangerous drop in blood pressure. Your prescriber will ensure none of these medicines are part of your treatment plan before approving tadalafil.

What you need to know

• Tadalafil and montelukast can generally be taken together with no major interaction commonly reported.
• Always declare all medicines during your ED consultation so your prescriber can review your full medical history.
• Never take tadalafil with nitrates, nicorandil, riociguat, or poppers—these combinations are dangerous.
• Continue taking montelukast as prescribed while using tadalafil unless your doctor advises otherwise.
• Seek urgent help for an erection lasting over four hours, chest pain, or sudden vision or hearing loss.

Other medicines that can interact with tadalafil

While tadalafil and montelukast do not interact significantly, tadalafil can interact with several other types of medicine. Alpha-blockers (such as doxazosin, tamsulosin, or alfuzosin), used for prostate problems or high blood pressure, can increase the risk of dizziness or low blood pressure when combined with tadalafil [4]. If you take an alpha-blocker, you should be stable on that medicine before starting tadalafil, and your prescriber will usually recommend the lowest dose of tadalafil to begin with.

Potent CYP3A4 inhibitors—medicines that slow down the breakdown of tadalafil in the liver—can raise tadalafil levels in your blood. These include some antifungals (ketoconazole, itraconazole), certain antibiotics (clarithromycin), and HIV medicines (ritonavir, cobicistat) [4]. If you take any of these, your prescriber may need to adjust your tadalafil dose or choose a different ED treatment.

Conversely, CYP3A4 inducers such as rifampicin, carbamazepine, phenytoin, and St John's wort can make tadalafil less effective by speeding up its breakdown. Grapefruit juice can also raise tadalafil levels and should be avoided. Other blood-pressure medicines may add to the blood-pressure-lowering effect of tadalafil, causing dizziness, but this is usually manageable and must be reviewed by your prescriber [4].

Medicines you must never take with tadalafil

Do not take tadalafil if you use nitrates for chest pain (angina), such as glyceryl trinitrate (GTN) spray, isosorbide mononitrate, or isosorbide dinitrate. Do not take tadalafil with nicorandil (another angina medicine) or riociguat (used for pulmonary hypertension). These combinations can cause a severe and potentially life-threatening drop in blood pressure [4].

Do not take tadalafil with recreational drugs known as 'poppers' (amyl nitrite or alkyl nitrites), as these also contain nitrates. Never take tadalafil alongside another PDE5 inhibitor (such as sildenafil or vardenafil) at the same time, as this increases the risk of side effects without improving effectiveness [4].

Practical advice for taking tadalafil with montelukast

If you have been prescribed montelukast for asthma or allergies and you are considering tadalafil for erectile dysfunction, continue taking your montelukast exactly as your doctor has instructed. Montelukast is usually taken once daily in the evening, and you should not change the timing or dose without medical advice. Tadalafil can be taken at a different time of day, depending on whether you choose the on-demand or daily version.

For on-demand tadalafil (10mg or 20mg), take one tablet at least 30 minutes before you plan to have sex. The effect can last up to 36 hours, so you do not need to time it precisely [4]. For daily tadalafil (2.5mg or 5mg), take one tablet at the same time each day, regardless of when you plan to be sexually active. You can take tadalafil with or without food, and it will not interfere with your montelukast.

If you experience any unexpected symptoms after starting tadalafil—such as dizziness, chest pain, or difficulty breathing—stop taking tadalafil and seek medical advice promptly. While these symptoms are unlikely to be caused by an interaction with montelukast, they should always be checked by a healthcare professional. Keep both your GP and your pharmacist informed of all the medicines you are taking.

When to get urgent help

• Erection lasting more than four hours (priapism)—go to A&E immediately
• Sudden loss of vision or hearing—stop tadalafil and seek urgent medical help
• Chest pain during sexual activity—stop and call 999 if pain does not resolve quickly
• Severe dizziness or fainting after taking tadalafil—seek same-day medical advice
• Allergic reaction (rash, swelling of face or throat, difficulty breathing)—call 999

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

When to seek medical advice about tadalafil and montelukast

You should speak to your doctor or pharmacist before starting tadalafil if you have any concerns about taking it with montelukast or any other medicine. If you have recently been prescribed a new medicine, or if your montelukast dose has been changed, mention this during your ED consultation. Your prescriber needs a complete and up-to-date list of all your medicines to make a safe decision.

Seek urgent medical help if you experience an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or chest pain during sexual activity while taking tadalafil [4]. These are rare but serious side effects that require immediate attention. Call 999 or go to A&E if you experience these symptoms.

If you develop new or worsening asthma symptoms while taking tadalafil, contact your GP or asthma nurse. Although tadalafil does not interact with montelukast, any change in your breathing should be assessed. Similarly, if you notice side effects from tadalafil such as headache, indigestion, back pain, or flushing, and these do not settle, speak to your pharmacist or prescriber for advice [4].

How Cured Pharmacy can help

Cured Pharmacy is a GPhC-registered online pharmacy (GPhC 9012511) offering a confidential, pharmacist-led consultation service for erectile dysfunction. After you complete a short online questionnaire, a UK-registered prescriber will review your answers, including all the medicines you currently take such as montelukast, and decide whether tadalafil or another ED treatment is safe and suitable for you.

If approved, your medicine is dispensed by our pharmacy team and delivered discreetly to your door. Tadalafil is available from £7.95, and first-time customers can use code Ednew for 20% off. We also offer a range of other ED treatments, including sildenafil (from £0.45), vardenafil, and avanafil, so your prescriber can recommend the option that best fits your needs and medical history.