Can You Take Sildenafil and Tamsulosin Together?
Learn how these medicines interact and what precautions you need, with support from our UK pharmacist-led service.
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Sildenafil and Tamsulosin: Understanding the Interaction
Published: 16 October 2026
Many men wonder whether sildenafil and tamsulosin can be taken together safely. The short answer is yes, but only under careful medical supervision, because both medicines can lower blood pressure and the combination increases the risk of dizziness or fainting. Tamsulosin is an alpha-blocker used to treat urinary symptoms of an enlarged prostate, while sildenafil is a PDE5 inhibitor that helps with erectile dysfunction (ED). Your prescriber will check that you are stable on tamsulosin and start you on the lowest effective dose of sildenafil to minimise risk.
Key takeaways
- Sildenafil and tamsulosin can be taken together, but only under medical supervision due to blood pressure risks.
- You must be stable on tamsulosin before starting sildenafil, usually at the lowest dose of 25 mg.
- Both medicines can lower blood pressure; rise slowly and watch for dizziness, especially at first.
- Declare all your medicines during your online consultation so the prescriber can check for interactions.
- Seek urgent help if you have an erection lasting over four hours, sudden vision or hearing loss, or chest pain.
What is sildenafil and tamsulosin used for?
Sildenafil (the active ingredient in Viagra) is a PDE5 inhibitor licensed to treat erectile dysfunction in men [3]. It works by relaxing blood vessels in the penis, allowing more blood to flow in when you are sexually aroused. Sildenafil is typically taken about one hour before sexual activity at doses of 25 mg, 50 mg or 100 mg, and its effect lasts for around four to six hours. It does not cause an erection on its own; sexual stimulation is still needed.
Tamsulosin is an alpha-blocker prescribed to relieve urinary symptoms caused by benign prostatic hyperplasia (BPH), or an enlarged prostate [12]. It relaxes the muscles in the prostate and bladder neck, making it easier to pass urine. Tamsulosin is usually taken once daily, and many men take it long-term to manage their symptoms. Because both ED and prostate problems become more common with age, it is not unusual for men to need both medicines at the same time.
How do sildenafil and tamsulosin interact?
Both sildenafil and tamsulosin can lower blood pressure, and when taken together this effect can add up [3][12]. Tamsulosin relaxes smooth muscle in blood vessels as well as in the prostate, which can cause a drop in blood pressure, especially when you stand up (a condition called postural hypotension). Sildenafil also widens blood vessels throughout the body, not just in the penis. When you combine the two, the risk of dizziness, light-headedness or even fainting increases, particularly in the first few hours after taking sildenafil.
This interaction is well recognised and is not an absolute contraindication—it does not mean you cannot take the medicines together. However, it does require careful prescribing. Your doctor or pharmacist will ensure you have been on a stable dose of tamsulosin for some time (usually at least a few weeks) before starting sildenafil, and they will recommend the lowest effective dose of sildenafil to begin with. This cautious approach helps your body adjust and reduces the chance of a sudden drop in blood pressure.
Why the interaction happens
Alpha-blockers like tamsulosin work by blocking alpha-1 receptors in smooth muscle. These receptors are found not only in the prostate and bladder neck but also in blood vessel walls. When tamsulosin blocks these receptors, blood vessels relax and widen slightly, which can lower blood pressure. Sildenafil, on the other hand, inhibits an enzyme called phosphodiesterase type 5 (PDE5), leading to increased levels of a chemical that relaxes blood vessels. The combined effect on blood vessels is what creates the risk of low blood pressure, especially when moving from sitting or lying down to standing.
At a glance
What does your prescriber check before prescribing sildenafil and tamsulosin together?
When you request sildenafil through an online consultation at Cured Pharmacy, our UK-registered prescribers will ask detailed questions about all your current medicines, including tamsulosin. They will check how long you have been taking tamsulosin, whether your dose is stable, and whether you have experienced any side effects such as dizziness or fainting. If you have recently started tamsulosin or your dose has recently been increased, the prescriber may advise waiting until you are stable before adding sildenafil.
The prescriber will also review your blood pressure history and ask about any symptoms of low blood pressure, such as feeling faint when you stand up. They will consider your overall cardiovascular health, because men with heart disease or those taking other blood-pressure-lowering medicines need extra caution. If sildenafil is deemed suitable, you will usually be started on the lowest dose (25 mg) to see how you tolerate the combination. The prescriber may also advise you to take sildenafil at a different time of day from tamsulosin, or to avoid taking both medicines close together, to reduce the peak effect on blood pressure.
Other medicines that are checked
Your prescriber will also check for any medicines that are absolutely contraindicated with sildenafil. These include nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, and recreational drugs known as 'poppers' (amyl or alkyl nitrites). If you take any of these, do not take sildenafil, as the combination can cause a dangerous drop in blood pressure. Other medicines that can interact include potent CYP3A4 inhibitors (such as ritonavir, ketoconazole or clarithromycin), which can raise sildenafil levels and require dose adjustment, and other blood-pressure medicines, which may add to the blood-pressure-lowering effect [3].
Starting sildenafil when you are already on tamsulosin
If you are already taking tamsulosin and your prescriber approves sildenafil, you will typically start with a 25 mg dose. This is half the usual starting dose, and it allows your body to adjust to the combination. Take sildenafil about one hour before you plan to have sex, on an empty stomach or after a light meal (a heavy, fatty meal can delay absorption). Avoid taking it at the same time as your tamsulosin dose if possible, to spread out the blood-pressure-lowering effects.
When you first take sildenafil, be cautious about standing up quickly, especially in the first few hours. Sit on the edge of the bed for a moment before standing, and if you feel dizzy or light-headed, sit or lie down until it passes. Most men tolerate the combination well once they are stable on both medicines, but it is important to listen to your body. If you experience persistent dizziness, fainting, or any chest pain, stop taking sildenafil and contact your GP or pharmacist for advice. If the 25 mg dose is well tolerated but not quite effective enough, your prescriber may consider increasing the dose to 50 mg after reviewing your response.
Top tip for this combination
If you take tamsulosin in the morning, take sildenafil in the evening when needed. Spacing them out helps reduce the risk of a sudden drop in blood pressure and makes the combination safer.
Warning signs and when to seek help with sildenafil and tamsulosin
While most men can take sildenafil and tamsulosin together safely, you should be aware of warning signs that need prompt attention. If you experience an erection that lasts longer than four hours (priapism), seek emergency medical help immediately, as this can cause permanent damage. Sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing (sometimes with ringing in the ears or dizziness), are rare but serious side effects that require urgent medical attention.
If you develop chest pain during or after sexual activity, stop and seek medical help. Do not take nitrate medicines (such as GTN spray) to relieve chest pain if you have taken sildenafil in the past 24 hours, as this combination can be dangerous. If you feel very dizzy, faint, or experience a rapid or irregular heartbeat, sit or lie down and contact your GP or call NHS 111 for advice. Severe headache, nausea, or visual disturbances should also be reported to a healthcare professional.
Managing side effects
Common side effects of sildenafil include headache, facial flushing, indigestion and nasal congestion [3]. These are usually mild and temporary. Tamsulosin can cause dizziness, especially when you first start taking it or when the dose is increased. When you take both medicines, you may notice these side effects more, particularly dizziness. Drinking plenty of water, avoiding heavy alcohol, and rising slowly from sitting or lying positions can all help. If side effects are troublesome or do not settle after a few doses, speak to your prescriber about adjusting the dose or timing of your medicines.
Practical tips for taking sildenafil and tamsulosin safely
To get the best results and minimise risk when taking sildenafil and tamsulosin together, follow these practical tips. First, make sure you are stable on tamsulosin before starting sildenafil—ideally you should have been taking the same dose for at least a few weeks without significant side effects. Take sildenafil about one hour before sexual activity, and try to avoid taking it at exactly the same time as your tamsulosin dose. For example, if you take tamsulosin in the morning, consider taking sildenafil in the evening when needed.
Limit alcohol intake when using sildenafil, as alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect, increasing the risk of dizziness [1]. Avoid grapefruit juice, which can raise sildenafil levels in your blood. Stay well hydrated, and be cautious when standing up, especially in the first few hours after taking sildenafil. If you are prescribed a new medicine or your tamsulosin dose changes, let your prescriber know before taking your next dose of sildenafil, as this may affect the safety of the combination. Never take more than one dose of sildenafil in 24 hours, and do not combine it with other ED treatments unless specifically advised by your prescriber.
Alternatives if the combination is not suitable
If you cannot tolerate sildenafil with tamsulosin, or if your prescriber feels the combination carries too much risk in your case, there are other options. Tadalafil (Cialis) is another PDE5 inhibitor that can be used with alpha-blockers, though the same caution applies [4]. Some men find the longer duration of tadalafil (up to 36 hours) more convenient. Vardenafil and avanafil are also PDE5 inhibitors with similar interactions [5][6]. Non-tablet treatments such as vacuum erection devices, alprostadil cream (Vitaros) or alprostadil injections (Caverject) may be considered if oral medicines are not suitable [7]. Your prescriber will discuss the best option for your individual circumstances.
When to get urgent help
- Erection lasting longer than 4 hours (priapism)—go to A&E immediately
- Sudden loss of vision in one or both eyes—seek urgent medical attention
- Sudden loss or decrease in hearing, possibly with ringing or dizziness—contact a doctor urgently
- Chest pain during or after sex—stop activity and seek medical help; do not take nitrates if you have used sildenafil in the past 24 hours
- Severe dizziness, fainting, or rapid/irregular heartbeat—sit or lie down and call NHS 111 or your GP
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]
- 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.
Common Questions
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Can I take sildenafil and tamsulosin on the same day?
Yes, you can take them on the same day, but it is best to avoid taking them at exactly the same time. For example, take tamsulosin in the morning and sildenafil in the evening when needed, to spread out the blood-pressure-lowering effects.
What dose of sildenafil should I start with if I am on tamsulosin?
Your prescriber will usually start you on 25 mg of sildenafil, which is the lowest dose, to see how you tolerate the combination. If this is well tolerated but not effective enough, the dose may be increased to 50 mg.
Will I definitely get dizzy if I take sildenafil and tamsulosin together?
Not necessarily. Many men tolerate the combination well, especially if they are stable on tamsulosin and start sildenafil at a low dose. However, dizziness is a possible side effect, so take precautions such as rising slowly from sitting or lying down.
Can I take tadalafil instead of sildenafil if I am on tamsulosin?
Yes, tadalafil can also be used with tamsulosin, and the same precautions apply. You must be stable on tamsulosin and start tadalafil at a low dose. Your prescriber will advise which PDE5 inhibitor is most suitable for you.
Do I need to stop tamsulosin before starting sildenafil?
No, you do not need to stop tamsulosin. In fact, you should be stable on tamsulosin before starting sildenafil. Do not stop or change any prescribed medicine without advice from your doctor or pharmacist.
What should I do if I feel faint after taking sildenafil and tamsulosin?
Sit or lie down immediately until the feeling passes. If you continue to feel faint, or if you actually faint, contact your GP or call NHS 111 for advice. You may need a dose adjustment or a review of your medicines.
Can I drink alcohol when taking sildenafil and tamsulosin together?
It is best to limit alcohol, as it can worsen erectile dysfunction and add to the blood-pressure-lowering effect of both medicines, increasing the risk of dizziness. One or two units is usually fine, but avoid heavy drinking.
How long do I need to wait after starting tamsulosin before I can take sildenafil?
You should be on a stable dose of tamsulosin for at least a few weeks before starting sildenafil. Your prescriber will check this during your consultation and advise when it is safe to start.
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Medically reviewed by
Tarun Kumar, Superintendent Pharmacist (GPhC 2233073)