Vardenafil and Riociguat: Do Not Take Together

Vardenafil and Riociguat: A Dangerous Combination

Published: 4 November 2026

Vardenafil and riociguat must never be taken together. This combination is contraindicated because both medicines lower blood pressure through related mechanisms, and taking them together can cause a sudden, dangerous drop in blood pressure that may lead to fainting, stroke, or heart attack. If you have been prescribed riociguat for pulmonary hypertension, vardenafil and all other PDE5 inhibitor erectile dysfunction treatments are not safe options for you.

What is vardenafil and riociguat used for?

Vardenafil (brand name Levitra) is a prescription medicine used to treat erectile dysfunction in men. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis to improve blood flow during sexual stimulation [5]. Vardenafil is typically taken 25 to 60 minutes before sexual activity, and its effects can last for several hours. It is available in 5mg, 10mg, and 20mg tablets, and you should not take it more than once in 24 hours.

Riociguat (brand name Adempas) is a completely different type of medicine used to treat pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension—serious conditions affecting blood pressure in the lungs. Riociguat is a guanylate cyclase stimulator that works by relaxing and widening blood vessels in the lungs, reducing the strain on the heart. It is taken as a regular daily tablet, usually three times a day, and requires careful monitoring by a specialist.

Although these medicines treat very different conditions, they both affect blood pressure regulation in the body. This overlap creates a serious safety concern when they are combined, which is why vardenafil and riociguat are never prescribed together.

Why vardenafil and riociguat must not be taken together

The combination of vardenafil and riociguat is strictly contraindicated, meaning it is medically prohibited. Both medicines work on pathways that involve a chemical messenger called cyclic GMP, which causes blood vessels to relax and widen. Vardenafil prevents the breakdown of cyclic GMP in the penis, while riociguat stimulates its production in the lungs. When taken together, these effects combine and amplify each other throughout the body's circulation [5].

This amplification can lead to a severe and potentially life-threatening drop in blood pressure. Symptoms may include extreme dizziness, fainting, blurred vision, confusion, chest pain, or collapse. In the worst cases, the sudden fall in blood pressure can reduce blood flow to vital organs including the heart and brain, leading to heart attack or stroke.

The risk applies to all PDE5 inhibitors, not just vardenafil. If you take riociguat, you must also avoid sildenafil (Viagra), tadalafil (Cialis), and avanafil (Spedra). There are no safe doses or timing strategies that make this combination acceptable—the interaction is absolute, and the medicines must never be used together under any circumstances.

How the interaction works in plain English

Think of blood pressure regulation like a carefully balanced system of taps and drains. Riociguat opens the taps wider (stimulating cyclic GMP production), while vardenafil blocks the drains (preventing cyclic GMP breakdown). When both happen at once, the system floods—blood vessels dilate too much, blood pressure drops dangerously, and not enough blood reaches your brain and heart. This is why the combination is never safe, regardless of dose or timing.

What your prescriber checks before approving vardenafil

Before any erectile dysfunction treatment is prescribed, a UK prescriber must review your full medical history and current medications. This includes checking for any conditions or medicines that would make PDE5 inhibitors unsafe. The consultation will specifically ask whether you take any medicines for chest pain, heart problems, or lung conditions, because these are the areas where dangerous interactions most commonly occur [2].

If you take riociguat, the prescriber will identify this as an absolute contraindication and will not approve vardenafil or any other PDE5 inhibitor. The online consultation form at Cured Pharmacy asks detailed questions about your current medicines, including their names, doses, and what they are for. It is essential that you list every medicine you take—whether prescribed by your GP, a hospital specialist, bought over the counter, or ordered online.

The prescriber will also check for other contraindications such as nitrate medicines (GTN spray, isosorbide mononitrate), nicorandil, recent heart attack or stroke, severe heart failure, very low blood pressure, and certain eye conditions. If vardenafil is not suitable, the prescriber may discuss alternative treatments for erectile dysfunction that do not interact with riociguat, such as vacuum devices, although options are limited. In many cases, managing the underlying cause of ED—such as diabetes, high blood pressure, or psychological factors—becomes the focus [1].

Other medicines that interact with vardenafil

Beyond riociguat, several other medicine groups have important interactions with vardenafil. Nitrate medicines used for angina—such as glyceryl trinitrate (GTN) spray, isosorbide mononitrate, and isosorbide dinitrate—are absolutely contraindicated with all PDE5 inhibitors for the same reason as riociguat: they cause a dangerous drop in blood pressure. Nicorandil, another angina medicine, carries the same risk. Recreational drugs known as 'poppers' (amyl nitrite or alkyl nitrites) also contain nitrates and must never be used with vardenafil [5].

Alpha-blocker medicines for prostate symptoms or high blood pressure—such as tamsulosin, doxazosin, alfuzosin, and terazosin—can also lower blood pressure when combined with vardenafil, though this interaction is manageable. If you take an alpha-blocker, your prescriber will usually start you on the lowest dose of vardenafil and ensure you are stable on the alpha-blocker first. You should not take vardenafil within four hours of an alpha-blocker dose.

Certain antifungal medicines (ketoconazole, itraconazole), antibiotics (clarithromycin, erythromycin), and HIV medicines (ritonavir, cobicistat, or Paxlovid) can increase vardenafil levels in the blood, raising the risk of side effects. Vardenafil is often contraindicated or requires dose adjustment with these medicines—your prescriber will check the specific combination. Medicines that speed up liver enzymes, such as rifampicin, carbamazepine, phenytoin, and St John's wort, can make vardenafil less effective [5].

Declaring all your medicines during the consultation

Always declare every medicine you take during your online consultation, including those prescribed by different doctors, herbal remedies, supplements, and anything bought without a prescription. If you are unsure of a medicine's name, describe what it is for or check the label. Never assume a medicine is 'not important enough' to mention—interactions can occur with common treatments, and your safety depends on the prescriber having complete information.

Warning signs and when to seek urgent help

If you have accidentally taken vardenafil while on riociguat, or if you experience symptoms of very low blood pressure after taking vardenafil, you need urgent medical attention. Warning signs include severe dizziness or feeling faint, especially when standing up; blurred vision or difficulty seeing; confusion or difficulty thinking clearly; a rapid or irregular heartbeat; chest pain or tightness; difficulty breathing; or collapsing. Do not wait to see if symptoms improve—call 999 or go to A&E immediately.

Other urgent situations with vardenafil include an erection lasting longer than four hours (priapism), which requires emergency treatment to prevent permanent damage; sudden loss of vision in one or both eyes, which may indicate a serious condition called NAION; or sudden decrease or loss of hearing, sometimes with ringing in the ears. Chest pain during or after sexual activity also requires urgent assessment, as it may indicate that your heart is under strain [5].

If you develop severe side effects such as an allergic reaction (swelling of the face, lips, tongue or throat, difficulty breathing, severe skin rash), seek immediate help. Less urgent but still important: if you experience persistent side effects such as prolonged headache, flushing, indigestion, nasal congestion, or back pain, contact your GP or pharmacist for advice. Most side effects are mild and temporary, but your healthcare team can help you manage them or adjust your treatment if needed.

Practical advice if you take riociguat and have erectile dysfunction

If you take riociguat for pulmonary hypertension and are experiencing erectile dysfunction, it is important to discuss this with your specialist or GP rather than attempting to obtain ED treatment online without declaring your riociguat use. Erectile dysfunction is common in men with chronic health conditions, and there may be other factors contributing to the problem—such as the underlying illness itself, psychological stress, or other medicines you take [1].

Your doctor may be able to address some of these factors. For example, optimising the management of your pulmonary hypertension, reviewing other medicines that might contribute to ED, or referring you for psychological support can all help. Lifestyle measures such as stopping smoking, reducing alcohol, losing weight if needed, and increasing physical activity (within the limits advised for your heart and lung condition) can also improve erectile function over time [2].

Non-drug treatments for erectile dysfunction include vacuum erection devices, which use a pump to draw blood into the penis and a ring to maintain the erection. These devices do not interact with riociguat and may be a safe option. In some cases, a specialist may consider other prescription treatments such as alprostadil, which works by a different mechanism and does not have the same interaction with riociguat, though this requires careful assessment [7]. Never stop or reduce your riociguat without medical advice, as this could worsen your pulmonary hypertension. Equally, never take vardenafil or any PDE5 inhibitor while on riociguat, even if you have seen it advertised or recommended online.

How Cured Pharmacy keeps you safe

At Cured Pharmacy, every request for erectile dysfunction treatment is reviewed by a UK-registered prescriber. The online consultation asks detailed questions about your medical history and current medicines specifically to identify unsafe combinations like vardenafil and riociguat. If you declare that you take riociguat, the prescriber will not approve a PDE5 inhibitor and will advise you to discuss alternative options with your specialist. This process is designed to protect your safety and ensure that treatment is only supplied when it is clinically appropriate.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 4 November 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 4 November 2026]
3. Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 4 November 2026]
4. Joint Formulary Committee. (n.d.). Alprostadil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/alprostadil/ [accessed 4 November 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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