Vardenafil and Bosentan: Can They Be Taken Together?

Vardenafil and Bosentan: Understanding the Interaction

Published: 28 October 2026

Vardenafil and bosentan can interact because both medicines affect blood pressure, and bosentan significantly reduces the levels of vardenafil in your body. Vardenafil is a PDE5 inhibitor used to treat erectile dysfunction (ED), while bosentan is an endothelin receptor antagonist prescribed for pulmonary arterial hypertension. If you're taking bosentan and experiencing ED, your prescriber will carefully assess whether vardenafil or an alternative treatment is suitable, taking into account the reduced effectiveness and your overall cardiovascular health.

What Is Vardenafil and How Does It Work?

Vardenafil (generic Levitra) is a prescription medicine licensed in the UK to treat erectile dysfunction in adult men [5]. It belongs to a class of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you're sexually aroused. Vardenafil is available in 5mg, 10mg, and 20mg tablets and typically starts working within 25 to 60 minutes of taking it [5].

You should take vardenafil about 25–60 minutes before sexual activity, and the effect usually lasts for several hours. The medicine only works when you're sexually stimulated—it won't cause an erection on its own. The usual starting dose is 10mg, taken as needed, with a maximum of one dose per day [5]. Your prescriber may adjust the dose depending on how well it works for you and whether you experience any side effects.

Common side effects of vardenafil include headache, flushing, nasal congestion, and indigestion. More serious but rare side effects include sudden vision or hearing loss, chest pain during sex, or an erection lasting more than four hours (priapism), all of which require urgent medical attention [5]. Vardenafil is not suitable for everyone, particularly men for whom sexual activity is inadvisable due to heart problems, or those taking certain other medicines.

What Is Bosentan and Why Is It Prescribed?

Bosentan is a prescription medicine used to treat pulmonary arterial hypertension (PAH), a condition where the blood pressure in the arteries of the lungs is abnormally high. It works by blocking endothelin receptors, which helps to relax and widen the blood vessels in the lungs, reducing the strain on the heart and improving exercise capacity. Bosentan is usually taken twice daily as a long-term treatment for PAH.

Because PAH is a serious cardiovascular condition, men taking bosentan may also experience erectile dysfunction. ED can be caused by reduced blood flow, the underlying heart and lung condition itself, or the psychological impact of living with a chronic illness [1]. It's important to discuss ED openly with your doctor, as it may be a sign that your PAH or overall cardiovascular health needs closer monitoring.

Bosentan affects how the liver processes many other medicines, including vardenafil. It is a potent inducer of certain liver enzymes (CYP3A4 and CYP2C9), which means it speeds up the breakdown of other drugs in your body, potentially making them less effective. This interaction is particularly important when considering ED treatments, as the reduced drug levels may mean vardenafil doesn't work as well as expected.

Living with Pulmonary Arterial Hypertension

If you have PAH, your treatment plan will be carefully managed by a specialist team. Any new medicine, including those for ED, must be discussed with your cardiologist or pulmonary hypertension specialist before starting. They will consider how the ED treatment might interact with bosentan and your other medicines, and whether your heart and lungs are healthy enough for sexual activity. Never start or stop any medicine without medical advice.

How Do Vardenafil and Bosentan Interact?

Vardenafil and bosentan interact in two important ways. First, bosentan is a potent enzyme inducer that speeds up the breakdown of vardenafil in your liver, significantly lowering the amount of vardenafil in your bloodstream. This means vardenafil may not work as well, or may not work at all, if you're taking bosentan at the same time. Clinical studies have shown that bosentan can reduce vardenafil levels substantially, making it less effective for treating ED.

Second, both medicines can lower blood pressure. Vardenafil causes blood vessels to relax (which is how it helps with erections), and bosentan also widens blood vessels in the lungs. When taken together, there is a risk that your blood pressure could drop too much, leading to dizziness, fainting, or falls. This is particularly important if you're also taking other blood-pressure-lowering medicines or have underlying heart or lung problems.

Because of these interactions, your prescriber will need to assess whether vardenafil is the right choice for you, or whether an alternative ED treatment would be safer and more effective. They will review your full medication list, your PAH treatment plan, and your cardiovascular fitness before making a recommendation. You should never adjust the dose of vardenafil or bosentan yourself in an attempt to manage the interaction.

What Your Prescriber Will Check Before Prescribing

If you're taking bosentan and want treatment for ED, your prescriber will carry out a thorough assessment during your consultation. They will ask about your current medicines (including the dose and frequency of bosentan), your PAH diagnosis and how well controlled it is, and any other health conditions you have, particularly heart, liver, or kidney problems. They will also ask about your blood pressure and whether you've experienced dizziness or fainting.

Your prescriber will check whether sexual activity is safe for you. Men with severe heart failure, unstable angina, very low blood pressure, or a recent heart attack or stroke should not use PDE5 inhibitors like vardenafil [5]. Because PAH is a cardiovascular condition, this assessment is especially important. Your prescriber may consult with your cardiologist or PAH specialist before recommending an ED treatment.

They will also review whether vardenafil is likely to be effective given the interaction with bosentan, or whether an alternative treatment—such as a different PDE5 inhibitor, a topical treatment like Eroxon, or a non-oral option like alprostadil—might be more suitable. The goal is to find a treatment that works for you while keeping you safe.

Declaring All Your Medicines

Always tell your prescriber about every medicine you take, including prescription drugs, over-the-counter medicines, herbal remedies, and supplements. This includes bosentan, any other medicines for PAH (such as sildenafil for PAH, which is different from sildenafil for ED), blood pressure tablets, and treatments for other conditions. Complete and honest information helps your prescriber make the safest choice for you.

Are There Safer Alternatives to Vardenafil and Bosentan?

If you're taking bosentan, your prescriber may recommend an alternative to vardenafil that is less affected by the interaction. Tadalafil (generic Cialis) is another PDE5 inhibitor that may be considered, though it can also be affected by enzyme inducers like bosentan. Your prescriber will assess whether a higher dose or a different dosing schedule might help, or whether tadalafil's longer duration of action (up to 36 hours) makes it a more practical choice [4].

Sildenafil (generic Viagra) is also a PDE5 inhibitor and may be an option, though it too can be affected by bosentan. It's important to note that sildenafil is also used at higher doses to treat PAH itself, so your prescriber will need to ensure there's no confusion or duplication between your PAH treatment and any ED treatment [3]. Never take sildenafil for ED if you're already taking sildenafil (or another PDE5 inhibitor) for PAH.

Non-oral treatments may be more suitable if PDE5 inhibitors are not effective or safe for you. Eroxon is a topical gel that works locally and does not interact with bosentan; it's available without prescription after a pharmacy consultation. Alprostadil, available as a cream (Vitaros) or injection (Caverject), is another option that works differently from PDE5 inhibitors and may be prescribed if oral treatments are unsuitable [7]. Your prescriber will discuss the pros and cons of each option with you.

Practical Advice: What to Do If You're Taking Both Medicines

If your prescriber has decided that vardenafil is appropriate despite the interaction with bosentan, follow their instructions exactly. Do not take more than the prescribed dose, and do not take vardenafil more than once a day. Be aware that the medicine may not work as well as it would without the interaction, and discuss this openly with your prescriber if you find it ineffective—they may be able to suggest an alternative.

Monitor for signs of low blood pressure, such as dizziness, light-headedness, fainting, or feeling unusually tired. If you experience any of these symptoms, sit or lie down until you feel better, and contact your GP or prescriber for advice. Avoid drinking large amounts of alcohol, as this can worsen low blood pressure and make ED worse [1]. Grapefruit juice can also affect how your body processes vardenafil, so it's best to avoid it.

Never stop taking bosentan or adjust its dose without speaking to your PAH specialist, as this could worsen your pulmonary hypertension. Similarly, do not stop or change your ED treatment without advice. If you're prescribed a new medicine by another doctor, always tell them you're taking both bosentan and vardenafil (or another ED treatment) so they can check for further interactions. Keep all your healthcare providers informed about your full medication list.

When to Seek Urgent Help

Seek immediate medical help (call 999 or go to A&E) if you experience an erection lasting more than four hours, sudden loss of vision or hearing, severe chest pain during or after sex, or severe dizziness or fainting. These are rare but serious side effects that need urgent treatment. If you have any concerns about your symptoms or your medicines, contact your GP or prescriber as soon as possible.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 28 October 2026]
2. Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 28 October 2026]
3. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 28 October 2026]
4. Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 28 October 2026]
5. Joint Formulary Committee. (n.d.). Alprostadil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/alprostadil/ [accessed 28 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.