Sildenafil and Losartan: Can You Take Them Together?

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What is sildenafil and losartan used for?

Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed to treat erectile dysfunction. It works by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused [3]. Sildenafil is the active ingredient in Viagra and is available in 25mg, 50mg, and 100mg tablets. You take it about one hour before sexual activity, and it works only with sexual stimulation.

Losartan is an angiotensin II receptor blocker (ARB), a type of medicine used to treat high blood pressure (hypertension) and to protect the kidneys in people with diabetes [2]. It works by blocking the action of a hormone that narrows blood vessels, helping them to relax and widen. This lowers blood pressure and reduces the strain on your heart. Losartan is usually taken once or twice daily as a long-term treatment.

How do sildenafil and losartan interact?

Both sildenafil and losartan can lower blood pressure, though they do so through different mechanisms [3]. Losartan blocks receptors that cause blood vessels to constrict, while sildenafil relaxes smooth muscle in blood vessels by increasing levels of a chemical called cyclic GMP. When taken together, their blood-pressure-lowering effects can add up, which may lead to symptoms such as dizziness, light-headedness, or fainting, especially when standing up quickly.

This interaction is not classified as dangerous in the way that sildenafil combined with nitrates would be—there is no absolute contraindication. However, it does mean that your prescriber must assess your blood pressure control and cardiovascular health before approving sildenafil [2]. If your blood pressure is well controlled on losartan and you have no other significant heart problems, sildenafil is usually considered safe to use. Your prescriber may recommend starting on a lower dose of sildenafil to minimise the risk of a sudden drop in blood pressure.

Why this matters for your safety

A modest drop in blood pressure is usually well tolerated, but if it falls too low, you may feel dizzy or faint, particularly when moving from sitting to standing. This is why it is essential to be honest during your online consultation about all medicines you take, including losartan and any other blood pressure treatments. Your prescriber will review your current blood pressure readings, any history of heart disease, and whether you experience symptoms such as dizziness. This assessment ensures that sildenafil is appropriate and that the starting dose is right for you.

When to get urgent help

• Chest pain during or after sexual activity—call 999 immediately
• An erection lasting more than 4 hours (priapism)—go to A&E
• Sudden loss of vision or hearing—seek urgent medical help
• Severe dizziness or fainting that does not improve with rest—contact your GP or NHS 111
• Symptoms of a stroke (face drooping, arm weakness, speech difficulty)—call 999

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

What your prescriber checks before approving sildenafil and losartan together

During your online consultation at Cured Pharmacy, the prescriber will ask about your current blood pressure, how well it is controlled on losartan, and whether you have any symptoms of low blood pressure such as dizziness or fainting [2]. They will also ask about other cardiovascular conditions, including angina, heart failure, recent heart attack or stroke, and any other medicines you take. This thorough review is essential to ensure that sexual activity and sildenafil are safe for you.

If your blood pressure is stable and well controlled, the prescriber will usually approve sildenafil, often starting with a lower dose such as 25mg or 50mg. They may advise you to monitor how you feel after the first dose and to avoid sudden changes in posture (such as standing up quickly) to reduce the risk of dizziness. If you take other blood pressure medicines in addition to losartan, the prescriber will take these into account as well, as the combined effect on blood pressure may be greater.

Practical advice for taking sildenafil and losartan safely

If you are approved for sildenafil while taking losartan, take your sildenafil dose about one hour before you plan to have sex, and continue taking your losartan as prescribed by your GP [3]. Do not stop or change the dose of losartan without speaking to your doctor, as this could cause your blood pressure to rise. Avoid drinking large amounts of alcohol when using sildenafil, as alcohol can lower blood pressure further and may worsen erectile dysfunction.

Be aware of how you feel after taking sildenafil for the first time. If you experience dizziness, light-headedness, or fainting, sit or lie down and avoid driving or operating machinery. If these symptoms are severe or do not improve, contact your GP or NHS 111 for advice. It is also important to stay well hydrated and to avoid standing up too quickly, especially in the first few hours after taking sildenafil.

When to seek medical advice

Seek urgent medical help if you experience chest pain during or after sex, as this may indicate a heart problem that needs immediate assessment. You should also seek help if you have an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or severe dizziness that does not improve with rest [1][3]. These are rare but serious side effects that require prompt treatment. If you have any concerns about how sildenafil and losartan are working together, speak to your GP or pharmacist.

At a glance

Are there any blood pressure medicines you cannot take with sildenafil and losartan?

Sildenafil must never be taken with nitrate medicines (such as glyceryl trinitrate spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, or riociguat, as the combination can cause a dangerous and potentially life-threatening drop in blood pressure [3]. Do not take sildenafil with these medicines. Alkyl nitrites, commonly known as 'poppers', are also absolutely contraindicated with sildenafil.

Losartan itself is not contraindicated with sildenafil, but if you take an alpha-blocker (such as doxazosin, tamsulosin, or alfuzosin) for prostate symptoms or blood pressure, extra caution is needed. Alpha-blockers can also lower blood pressure significantly when combined with sildenafil, so your prescriber will ensure you are stable on the alpha-blocker and will start you on the lowest dose of sildenafil [2][3]. Always declare every medicine you take during your consultation, including over-the-counter treatments and herbal supplements such as St John's wort, which can reduce the effectiveness of sildenafil.

Other PDE5 inhibitors and losartan: what you need to know

If sildenafil is not suitable for you, or if you prefer a different option, other PDE5 inhibitors such as tadalafil (Cialis), vardenafil (Levitra), and avanafil (Spedra) are also available and can generally be used with losartan, subject to the same prescriber checks [4][5][6]. Tadalafil can be taken on-demand (10mg or 20mg at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low dose (2.5mg or 5mg). Vardenafil is taken 25–60 minutes before sex, and avanafil works within 15–30 minutes, making it one of the fastest-acting options.

The same principles apply: your prescriber will assess your blood pressure control, cardiovascular health, and all current medicines before approving any PDE5 inhibitor. You should never take more than one PDE5 inhibitor at the same time, as this increases the risk of side effects, including a dangerous drop in blood pressure. At Cured Pharmacy, all ED treatments require an online consultation reviewed by a UK-registered prescriber, ensuring that the medicine is safe and appropriate for you.

Choosing the right ED treatment for you

The choice between sildenafil, tadalafil, vardenafil, and avanafil often comes down to personal preference, how quickly you want the medicine to work, and how long you want the effect to last. Sildenafil and vardenafil are taken about an hour before sex and last for around four to six hours, while tadalafil can last up to 36 hours, offering more spontaneity. Avanafil works quickly, often within 15–30 minutes. Your prescriber can help you choose the most suitable option based on your lifestyle, medical history, and how you respond to treatment.

In summary

• Sildenafil and losartan can usually be taken together if your blood pressure is well controlled
• Both medicines can lower blood pressure, so your prescriber will assess your cardiovascular health first
• Never take sildenafil with nitrates, nicorandil, or riociguat—this combination is dangerous
• Start with a lower dose of sildenafil if you take losartan or other blood pressure medicines
• Seek urgent help if you experience chest pain, severe dizziness, or an erection lasting over four hours

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