Tadalafil and Riociguat: Do Not Take Together
Learn why this combination is dangerous and what ED treatments are safe if you take riociguat.
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Tadalafil and Riociguat: Why You Must Not Take Them Together
Published: 16 October 2026
Tadalafil and riociguat must never be taken together because the combination can cause a dangerous, potentially life-threatening drop in blood pressure [3][4]. Tadalafil is a PDE5 inhibitor used to treat erectile dysfunction (ED), while riociguat is a medicine prescribed for pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). Both medicines work by relaxing blood vessels, and when combined, their effects add up in a way that can cause severe harm. This page explains what each medicine does, why the interaction is so serious, and what to do if you're taking riociguat and considering ED treatment.
Key takeaways
- Tadalafil and riociguat must never be taken together due to the risk of severe low blood pressure.
- All PDE5 inhibitors are contraindicated with riociguat, not just tadalafil.
- Alternative ED treatments include alprostadil cream or injection and vacuum devices.
- Always tell your prescriber about every medicine you take, including those for long-term conditions.
- Seek urgent help if you have taken both medicines, even if you feel well.
What Is Tadalafil and How Does It Work?
Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction [4]. It works by blocking an enzyme called PDE5, which normally breaks down a substance called cyclic GMP. When PDE5 is blocked, cyclic GMP levels rise, causing the smooth muscle in the blood vessels of the penis to relax. This allows more blood to flow into the penis during sexual stimulation, helping to achieve and maintain an erection [4].
Tadalafil is available as generic tablets and under the brand name Cialis. It can be taken on-demand (10 mg or 20 mg at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low dose (2.5 mg or 5 mg) [4]. Sexual stimulation is still needed for the medicine to work. Tadalafil also has a blood-pressure-lowering effect throughout the body, which is why it interacts with certain other medicines.
At Cured Pharmacy, tadalafil is available on prescription after an online consultation reviewed by a UK-registered prescriber. You can choose from generic Tadalafil, Tadalafil 20mg (Teva), Avarante (tadalafil) 10mg, or branded Cialis, all with discreet delivery.
What Is Riociguat and Why Is It Prescribed?
Riociguat is a medicine used to treat two serious lung conditions: pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) [12]. These conditions involve high blood pressure in the arteries that supply the lungs, which makes the heart work harder and can lead to breathlessness, fatigue, and heart failure if untreated.
Riociguat works by stimulating an enzyme called soluble guanylate cyclase (sGC), which increases levels of cyclic GMP inside cells. This causes the blood vessels in the lungs (and elsewhere in the body) to relax and widen, reducing blood pressure and easing the strain on the heart [12]. Riociguat is taken as tablets, usually two or three times a day, and is prescribed by specialists who manage pulmonary hypertension.
Because riociguat raises cyclic GMP levels throughout the body, it has a powerful blood-pressure-lowering effect. This is why combining it with tadalafil—which also raises cyclic GMP—is so dangerous.
Other Names for Riociguat
Riociguat is sold under the brand name Adempas in the UK. If you see this name on your prescription or medicine box, it is the same medicine and the same interaction applies [12].
At a glance
Why Tadalafil and Riociguat Must Never Be Taken Together
The interaction between tadalafil and riociguat is classified as a contraindication, meaning the two medicines must not be used together under any circumstances [3][4]. Both medicines increase cyclic GMP levels in the body, but they do so through different mechanisms: tadalafil blocks the enzyme that breaks down cyclic GMP, while riociguat stimulates the enzyme that makes it. When taken together, the combined effect on cyclic GMP is much greater than either medicine alone.
This leads to excessive relaxation of blood vessels throughout the body, causing blood pressure to fall to dangerously low levels. Symptoms of severe hypotension (low blood pressure) include dizziness, fainting, blurred vision, confusion, nausea, and in the worst cases, shock or loss of consciousness [3][4]. The risk is present even if the two medicines are taken hours apart, because tadalafil can remain active in the body for up to 36 hours.
The contraindication applies to all PDE5 inhibitors, not just tadalafil. This means sildenafil (Viagra), vardenafil (Levitra), and avanafil (Spedra) are also unsafe to take with riociguat [3][5][6]. If you are taking riociguat for pulmonary hypertension, you must tell your prescriber before starting any ED treatment.
What Your Prescriber Checks Before Prescribing Tadalafil
Before tadalafil or any PDE5 inhibitor can be prescribed, a UK prescriber will ask detailed questions about your current medicines, medical history, and cardiovascular health [2][4]. One of the most important questions is whether you are taking riociguat, nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, or recreational drugs called 'poppers' (amyl or alkyl nitrites). All of these are absolute contraindications to PDE5 inhibitors [3][4].
The prescriber will also check for other conditions that make PDE5 inhibitors unsuitable, such as recent heart attack or stroke, unstable angina, severe heart failure, very low blood pressure, or a history of sudden vision loss (non-arteritic anterior ischaemic optic neuropathy, or NAION) [2][4]. If you take alpha-blockers for prostate symptoms or high blood pressure, the prescriber will ensure you are stable on that medicine and may start you on a lower dose of tadalafil to reduce the risk of dizziness [4].
At Cured Pharmacy, every order for tadalafil requires completion of an online medical questionnaire. A UK-registered prescriber reviews your answers before approving the prescription. This process is designed to identify unsafe combinations and ensure the medicine is right for you.
Medicines That Raise Tadalafil Levels
Some medicines slow down the breakdown of tadalafil in the liver, causing levels to rise and side effects to become more likely. These include potent CYP3A4 inhibitors such as ritonavir, cobicistat (found in some HIV medicines), ketoconazole, itraconazole, and clarithromycin [4]. If you take any of these, your prescriber will adjust the dose of tadalafil or may recommend a different ED treatment. Always declare every medicine you take, including those bought over the counter or prescribed by another doctor.
Always Declare Riociguat
If you take riociguat for pulmonary hypertension, you must tell every prescriber before starting any ED treatment. This interaction is life-threatening and applies to all PDE5 inhibitors, not just tadalafil.
Alternative ED Treatments If You Take Riociguat
If you are taking riociguat for pulmonary hypertension, all oral PDE5 inhibitors—including tadalafil, sildenafil, vardenafil, and avanafil—are contraindicated [3][4][5][6]. This means you cannot use any of the tablet treatments commonly prescribed for erectile dysfunction. However, ED is still treatable, and there are other options that work through different mechanisms and do not interact with riociguat.
One alternative is Vitaros, a prescription cream containing alprostadil that is applied directly to the tip of the penis a few minutes before sex [7]. Alprostadil works locally to relax blood vessels in the penis without affecting blood pressure throughout the body. Another option is Caverject, an alprostadil injection given into the side of the penis [7]. Both treatments require training from a healthcare professional and are usually considered when tablets are unsuitable or ineffective.
Vacuum erection devices (VEDs) are non-drug options that use a plastic cylinder and pump to draw blood into the penis, with a constriction ring placed at the base to maintain the erection [1][2]. These devices are available on the NHS and can be effective for many men. Your GP or a specialist can discuss which option is most suitable for your situation and provide a referral if needed.
What to Do If You've Taken Tadalafil and Riociguat Together
If you have taken tadalafil (or any other PDE5 inhibitor) while you are on riociguat, seek urgent medical advice immediately, even if you feel well [3][4]. The risk of a dangerous drop in blood pressure is highest within the first few hours, but because tadalafil can stay active for up to 36 hours, symptoms can develop later. Call 111 for advice, or go to A&E if you experience dizziness, fainting, chest pain, severe headache, blurred vision, or confusion.
Do not lie flat if you feel dizzy; instead, sit with your head between your knees or lie on your side. Do not drive or operate machinery. If you lose consciousness, the person with you should call 999 immediately and tell the paramedics which medicines you have taken. Carry a list of your current medicines (including riociguat) with you at all times, or use the NHS App to share your medical record with healthcare professionals.
If you were not aware of the interaction and have been prescribed both medicines by different doctors, contact both prescribers as soon as possible to review your treatment plan. Never stop taking riociguat suddenly without medical advice, as this can worsen your pulmonary hypertension. Your specialist will help you find a safe alternative for ED if needed.
Preventing Accidental Interactions
Always tell every doctor, pharmacist, or prescriber about all the medicines you take, including those for long-term conditions, over-the-counter products, herbal remedies, and recreational drugs. If you use an online pharmacy, read the medical questionnaire carefully and answer every question honestly. Cured Pharmacy's prescribers rely on the information you provide to keep you safe, and incomplete answers can lead to dangerous prescriptions being issued.
When to get urgent help
- Severe dizziness, fainting, or loss of consciousness after taking tadalafil and riociguat together – call 999 immediately.
- Chest pain, blurred vision, confusion, or rapid weak pulse – go to A&E or call 999.
- An erection lasting more than 4 hours (priapism) – go to A&E immediately to prevent permanent damage.
- Sudden loss of vision or hearing after taking tadalafil – stop the medicine and seek same-day medical advice.
- Chest pain during or after sex – stop activity, sit down, and call 999 if it does not ease quickly.
Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.
Scientific References
- NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 16 October 2026]
- National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 16 October 2026]
- Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 16 October 2026]
- Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 16 October 2026]
- Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 16 October 2026]
- Joint Formulary Committee. (n.d.). Avanafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/avanafil/ [accessed 16 October 2026]
- Joint Formulary Committee. (n.d.). Alprostadil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/alprostadil/ [accessed 16 October 2026]
- Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 16 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.
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Can I take tadalafil if I'm on riociguat for pulmonary hypertension?
No. Tadalafil and riociguat must never be taken together because the combination can cause a dangerous drop in blood pressure. All PDE5 inhibitors are contraindicated with riociguat.
What should I do if I've accidentally taken both medicines?
Seek urgent medical advice immediately by calling 111 or going to A&E, even if you feel well. Tell the healthcare team which medicines you have taken and when.
Are there any ED treatments I can use if I take riociguat?
Yes. Alprostadil cream (Vitaros) or injection (Caverject) and vacuum erection devices are alternatives that do not interact with riociguat. Speak to your GP or specialist about which option is suitable.
Does the interaction apply to all PDE5 inhibitors or just tadalafil?
The contraindication applies to all PDE5 inhibitors, including sildenafil (Viagra), vardenafil (Levitra), and avanafil (Spedra), not just tadalafil.
How long does tadalafil stay in the body?
Tadalafil can remain active for up to 36 hours, which is why the risk of interaction with riociguat lasts well beyond the time you take the tablet.
Can I take tadalafil if I used to take riociguat but have stopped?
You must discuss this with your prescriber. If riociguat has been stopped recently, it may still be in your system. Your doctor will check how long ago you stopped and whether it is safe to start tadalafil.
Will Cured Pharmacy's consultation pick up this interaction?
Yes. The online medical questionnaire asks specifically about riociguat, nitrates, and other contraindicated medicines. A UK-registered prescriber reviews every answer before approving any prescription for tadalafil.
What are the warning signs of dangerously low blood pressure?
Symptoms include severe dizziness, fainting, blurred vision, confusion, nausea, rapid or weak pulse, and loss of consciousness. If you experience any of these after taking tadalafil, call 999 immediately.
Medically reviewed by
Tarun Kumar, Superintendent Pharmacist (GPhC 2233073)