Tadalafil and Ustekinumab: Can They Be Taken Together?

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At a glance

What is tadalafil and ustekinumab used for?

Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction (ED) [3][4]. It works by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Tadalafil is available as an on-demand treatment (10 mg or 20 mg taken at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low-dose tablet (2.5 mg or 5 mg). It is the generic version of Cialis and requires sexual stimulation to work [1][4].

Ustekinumab is a biologic medicine that targets specific proteins in the immune system (interleukin-12 and interleukin-23). It is prescribed for moderate to severe plaque psoriasis, active psoriatic arthritis, and moderate to severe Crohn's disease [12]. Ustekinumab is given by injection under the skin, usually every 12 weeks after initial loading doses. It works by reducing inflammation and is not related to the cardiovascular or blood-vessel pathways that tadalafil affects.

Because these two medicines work through entirely different mechanisms in the body, they do not directly interfere with each other's action. However, your prescriber will still need to review your overall health, particularly your cardiovascular fitness, before approving tadalafil, as erectile dysfunction can sometimes be an early warning sign of heart disease or diabetes [1][2].

Is there an interaction between tadalafil and ustekinumab?

No major interaction is commonly reported between tadalafil and ustekinumab. Tadalafil is primarily metabolised by the liver enzyme CYP3A4, and ustekinumab does not significantly affect this enzyme [4][12]. Ustekinumab works on the immune system and does not alter blood pressure or the way tadalafil is broken down in the body.

That said, it is essential to declare all your current medicines—including ustekinumab—during your online consultation for tadalafil. Your prescriber will check for any individual factors that might affect safety, such as other medicines you take, your cardiovascular health, and any history of low blood pressure. Conditions that require ustekinumab, such as psoriasis or Crohn's disease, do not in themselves prevent the use of tadalafil, but your overall health picture matters [2].

If you are taking other medicines alongside ustekinumab—for example, blood-pressure tablets, alpha-blockers, or potent CYP3A4 inhibitors—those may interact with tadalafil. Your prescriber will review every medicine during the consultation to ensure the combination is safe for you. Never stop or change a prescribed medicine without speaking to your doctor or pharmacist first.

How tadalafil is processed in the body

Tadalafil is broken down mainly by the liver enzyme CYP3A4 and, to a lesser extent, CYP2C9 [4]. Medicines that strongly inhibit CYP3A4—such as ritonavir, cobicistat, ketoconazole, itraconazole, or clarithromycin—can raise tadalafil levels in the blood, requiring dose adjustments or avoidance. Conversely, medicines that induce CYP3A4 (such as rifampicin, carbamazepine, phenytoin, or St John's wort) can reduce tadalafil's effectiveness. Ustekinumab does not fall into either category, so it does not alter how tadalafil is metabolised [12].

What your prescriber checks before approving tadalafil and ustekinumab together

When you request tadalafil through Cured Pharmacy, a UK-registered prescriber reviews your online consultation to ensure the treatment is safe and appropriate for you. They will ask about all your current medicines, including ustekinumab, and check for any conditions or other drugs that might interact with tadalafil [2][4].

Key checks include your cardiovascular health (recent heart attack, stroke, unstable angina, or severe heart failure), blood pressure (very low blood pressure is a contraindication), and whether you take nitrates, nicorandil, riociguat, or another PDE5 inhibitor—all of which must never be combined with tadalafil. The prescriber will also review any alpha-blockers (such as doxazosin or tamsulosin), as these can add to the blood-pressure-lowering effect of tadalafil and require a lower starting dose [3][4].

If you are on other medicines that affect blood pressure or are metabolised by CYP3A4, the prescriber will assess whether tadalafil is suitable and, if so, which dose is safest. Because ustekinumab itself does not interact with tadalafil, the focus will be on your overall health and any other medicines you take. Always answer the consultation questions fully and honestly to ensure your safety.

What you need to know

• No major interaction is commonly reported between tadalafil and ustekinumab.
• Your prescriber reviews all medicines during consultation to ensure tadalafil is safe for you.
• Never take tadalafil with nitrates, nicorandil, riociguat, poppers, or another PDE5 inhibitor.
• Continue ustekinumab as prescribed; no dose adjustment needed when starting tadalafil.
• Seek urgent help for erection lasting over four hours or sudden vision or hearing loss.

Medicines that must never be taken with tadalafil

Certain medicines are absolutely contraindicated 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), nicorandil, riociguat, or amyl/alkyl nitrites (poppers). Do not take tadalafil alongside another PDE5 inhibitor (sildenafil, vardenafil, or avanafil) [3][4].

If you are prescribed a nitrate medicine for angina or chest pain, you must not use tadalafil. The combination can lead to a severe and potentially life-threatening fall in blood pressure. If you experience chest pain during sex while taking tadalafil, do not use a nitrate spray—seek urgent medical help and tell the healthcare professional that you have taken tadalafil [1][4].

Ustekinumab is not in any of these contraindicated categories, so the combination of tadalafil and ustekinumab does not carry this risk. However, always declare every medicine you take, including over-the-counter products and supplements, during your consultation.

Other medicines that may require caution

Alpha-blockers (doxazosin, tamsulosin, alfuzosin, terazosin, prazosin, silodosin, indoramin) can add to the blood-pressure-lowering effect of tadalafil, increasing the risk of dizziness or fainting. If you take an alpha-blocker, you should be stable on it before starting tadalafil, and your prescriber will usually recommend the lowest dose of tadalafil initially [4]. Other blood-pressure medicines can also add to this effect, so your prescriber will review them carefully. Grapefruit juice can raise tadalafil levels and should be avoided, and heavy alcohol can worsen erectile dysfunction and increase the risk of low blood pressure [4].

Practical advice for taking tadalafil and ustekinumab safely

If your prescriber approves tadalafil while you are on ustekinumab, follow the dosing instructions carefully. For on-demand tadalafil (10 mg or 20 mg), take one tablet at least 30 minutes before sexual activity; the effect can last up to 36 hours, so do not take more than one dose in 24 hours. For daily tadalafil (2.5 mg or 5 mg), take one tablet at the same time each day, regardless of when you plan to have sex. Tadalafil requires sexual stimulation to work—it will not cause an erection on its own [4].

Continue taking ustekinumab exactly as your specialist has prescribed. There is no need to adjust the timing of your ustekinumab injections around tadalafil use. If you develop any new symptoms or side effects after starting tadalafil, contact your GP or pharmacist for advice. Common side effects of tadalafil include headache, indigestion, back pain, muscle aches, and flushing; these are usually mild and temporary [4].

Store both medicines as directed on the packaging. Keep tadalafil in a cool, dry place away from children. If you miss a dose of daily tadalafil, take it as soon as you remember, but do not take two doses in one day. If you have any questions about your treatment, the pharmacist team at Cured Pharmacy is available to help.

When to get urgent help

• Erection lasting more than 4 hours (priapism)—call 999 or go to A&E immediately
• Sudden loss of vision in one or both eyes—stop tadalafil and seek urgent medical help
• Sudden hearing loss or ringing in the ears—stop tadalafil and contact your doctor
• Chest pain during or after sex—do not use nitrate spray; tell healthcare professionals you have taken tadalafil and seek urgent help
• Severe dizziness or fainting after taking tadalafil—seek same-day medical advice

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

When to seek urgent medical help while taking tadalafil

Seek immediate medical attention if you experience an erection lasting more than four hours (priapism), as this can cause permanent damage to the penis if not treated promptly. Call 999 or go to A&E straight away [1][4]. If you have sudden loss of vision in one or both eyes, stop taking tadalafil and seek urgent medical help, as this may be a sign of non-arteritic anterior ischaemic optic neuropathy (NAION), a rare but serious condition [4].

If you develop sudden hearing loss or ringing in the ears, stop tadalafil and contact your doctor immediately. If you experience chest pain during or after sex, do not use a nitrate medicine—tell the healthcare professional that you have taken tadalafil and seek urgent help [1][4]. These warning signs are rare, but it is important to know what to look out for.

If you have concerns about how tadalafil and ustekinumab are working together, or if you notice any unexpected symptoms, contact your GP or pharmacist for advice. Never stop taking ustekinumab without consulting your specialist, as this is a long-term treatment for your underlying condition. Erectile dysfunction treatment is only one part of your overall health, and your care team can help you manage all your medicines safely.

Why erectile dysfunction should always be assessed

Erectile dysfunction can be an early warning sign of cardiovascular disease, diabetes, or other health conditions [1][2]. If you are experiencing ED for the first time, it is important to see your GP for a full assessment, even if you are already under specialist care for another condition such as psoriasis or Crohn's disease. Your GP can check your blood pressure, cholesterol, blood sugar, and overall heart health, and refer you for further tests if needed. Treating ED with tadalafil is effective, but addressing any underlying health issues is equally important for your long-term wellbeing [2].

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