Can You Take Sildenafil and Alfuzosin Together?

Takes less than 2 minutes to complete 100% online

Key takeaways

• Sildenafil and alfuzosin can be taken together, but only under medical supervision due to blood pressure interaction
• You must be stable on alfuzosin first and start sildenafil at the lowest dose (25mg)
• Both medicines lower blood pressure, increasing the risk of dizziness when standing up
• Always tell your prescriber about all medicines you take, including alfuzosin, before starting sildenafil
• Seek urgent help if you experience chest pain, fainting, or an erection lasting over four hours

What is sildenafil and alfuzosin used for?

Sildenafil (the active ingredient in Viagra) is a medicine licensed to treat erectile dysfunction in men. It works by relaxing blood vessels in the penis, which increases blood flow and helps achieve and maintain an erection when sexually aroused [3]. Sildenafil is taken about an hour before sexual activity, and its effects can last for around four to five hours. It's available in 25mg, 50mg, and 100mg tablets, and you should not take it more than once a day.

Alfuzosin belongs to a group of medicines called alpha-blockers. It's prescribed to relieve urinary symptoms caused by benign prostatic hyperplasia (BPH), a non-cancerous enlargement of the prostate gland that can make it difficult to pass urine. Alfuzosin works by relaxing the muscles in the prostate and bladder neck, making it easier to urinate. It's usually taken once or twice daily, depending on the formulation your doctor has prescribed.

Both conditions—erectile dysfunction and prostate enlargement—are common in men over 50, so it's quite usual for a man to be prescribed both medicines. However, because they both affect blood pressure and blood vessels, their interaction needs to be managed carefully by a healthcare professional [2].

How do sildenafil and alfuzosin interact?

The main concern when taking sildenafil and alfuzosin together is that both medicines can lower blood pressure. Alfuzosin relaxes the 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 has a blood-pressure-lowering effect because it widens blood vessels throughout the body, not just in the penis [3].

When you take both medicines at the same time, these effects can add together, increasing the risk of dizziness, light-headedness, or fainting—particularly when you stand up quickly. In some cases, this drop in blood pressure can be significant enough to cause you to feel unwell or even lose consciousness. That's why it's essential that your prescriber knows you're taking alfuzosin before starting sildenafil, or vice versa.

The good news is that this interaction can be managed safely. Clinical guidelines recommend that if you're already stable on an alpha-blocker like alfuzosin (meaning you've been taking it for a while without problems), you can start sildenafil at the lowest effective dose. Your body will have adjusted to the blood-pressure effects of alfuzosin, and starting with a low dose of sildenafil minimises the additional drop in blood pressure [2][3].

Why the interaction happens

Both medicines work on smooth muscle in blood vessels, though through different mechanisms. Alfuzosin blocks alpha-1 receptors, which normally cause blood vessels and the prostate to contract. Sildenafil inhibits an enzyme called PDE5, which breaks down a chemical that keeps blood vessels relaxed. The result is that both medicines promote relaxation of blood vessels, and when used together, the combined effect on blood pressure can be greater than either medicine alone.

At a glance

What your prescriber will check before prescribing sildenafil and alfuzosin together

Before prescribing sildenafil to someone already taking alfuzosin, a prescriber will carry out a careful assessment. They'll ask how long you've been on alfuzosin and whether you've had any problems with dizziness or low blood pressure. If you've only recently started alfuzosin, they may advise waiting until you're stable on it before adding sildenafil. This usually means you've been taking the alpha-blocker for at least a few weeks without side effects.

Your prescriber will also check your current blood pressure and ask about any history of heart problems, fainting episodes, or other conditions that might make a drop in blood pressure more risky. They'll review all your other medicines to make sure there are no additional interactions that could complicate things. For example, if you're also taking other blood-pressure medicines, the combined effect needs to be considered.

If it's safe to proceed, the prescriber will usually start you on the lowest dose of sildenafil—typically 25mg—and advise you to take it at a different time of day from your alfuzosin if possible, to reduce the chance of both medicines peaking in your system at the same time. They'll also give you clear advice about what to watch out for and when to seek help [2][3].

Practical advice for taking sildenafil with alfuzosin safely

If your prescriber has confirmed it's safe for you to take sildenafil and alfuzosin together, there are several practical steps you can take to minimise the risk of side effects. First, always start with the lowest dose of sildenafil (usually 25mg) and see how you respond before considering a higher dose. Even if you've taken sildenafil before without alfuzosin, the combination changes things, so it's important to start low.

Be especially careful when standing up, particularly in the first few hours after taking sildenafil. Get up slowly from sitting or lying down, and if you feel dizzy or light-headed, sit or lie down immediately until the feeling passes. Avoid sudden changes in posture, and be cautious if you're getting up during the night to use the bathroom, as this is a common time for falls.

Limit alcohol when taking these medicines together. Alcohol also lowers blood pressure and can make dizziness worse. It can also make it harder to get an erection, which defeats the purpose of taking sildenafil in the first place. One or two units is usually fine, but heavy drinking should be avoided. Stay well hydrated, especially in hot weather, as dehydration can also contribute to low blood pressure.

Never take sildenafil more than once a day, and don't take a higher dose than your prescriber has recommended, even if the lower dose doesn't seem to work as well as you'd hoped. If the 25mg dose isn't effective, speak to your prescriber—they may be able to increase the dose cautiously or suggest an alternative approach. And always tell any healthcare professional you see (including your dentist or a pharmacist) that you're taking both medicines [3].

Timing your doses

Although there's no strict rule about separating the doses, some prescribers suggest taking sildenafil at a different time of day from alfuzosin if your schedule allows. For example, if you take alfuzosin in the morning, you might take sildenafil in the evening before sexual activity. This can help reduce the chance of both medicines having their maximum blood-pressure-lowering effect at exactly the same time, though the most important thing is simply to start with a low dose and monitor how you feel.

Warning signs and when to seek help with sildenafil and alfuzosin

Most men who take sildenafil and alfuzosin together do so without serious problems, but it's important to know the warning signs that something isn't right. The most common issue is feeling dizzy or light-headed, especially when standing up. If this happens, sit or lie down straight away and let it pass. If dizziness is severe, happens frequently, or is accompanied by fainting, you should contact your GP or prescriber as soon as possible.

Chest pain during or after sexual activity is a medical emergency. Stop what you're doing, sit down, and call 999. Do not take GTN spray or any nitrate medicine if you've taken sildenafil in the past 24 hours, as the combination can cause a dangerous drop in blood pressure. Make sure the paramedics or hospital staff know you've taken sildenafil.

Other warning signs include an erection that lasts longer than four hours (priapism), sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing, sometimes with ringing in the ears. All of these are rare but require urgent medical attention. If you experience any of these symptoms, go to A&E or call 999 immediately [3].

If you develop new or worsening symptoms after starting the combination—such as persistent headaches, flushing, indigestion, or nasal congestion—these are usually mild side effects of sildenafil, but mention them to your prescriber if they're troublesome. They may be able to adjust your dose or suggest ways to manage them.

Alternatives and other considerations for men taking alfuzosin

If sildenafil and alfuzosin together cause too many side effects, or if your prescriber feels the combination isn't suitable for you, there are other options. Tadalafil (Cialis) is another PDE5 inhibitor that works in a similar way to sildenafil but has a longer duration of action—up to 36 hours. It can also be taken as a low daily dose (2.5mg or 5mg), which some men find more convenient. However, tadalafil has the same interaction with alfuzosin as sildenafil does, so the same precautions apply [4].

Other PDE5 inhibitors include vardenafil (Levitra) and avanafil (Spedra). All of these medicines can interact with alpha-blockers, so switching to a different PDE5 inhibitor won't necessarily solve the problem if the issue is the interaction itself. Your prescriber will help you weigh up the options based on your individual circumstances.

In some cases, your doctor might consider adjusting your alfuzosin or switching you to a different alpha-blocker, though this depends on how well your prostate symptoms are controlled. Alternatively, non-tablet treatments for erectile dysfunction—such as vacuum erection devices, alprostadil injections or cream, or even psychological support if anxiety is a factor—might be worth discussing [2].

It's also important to address any underlying causes of erectile dysfunction. ED can be an early warning sign of cardiovascular disease or diabetes, so if you haven't already done so, see your GP for a general health check. Lifestyle changes—such as losing weight if needed, exercising regularly, stopping smoking, and reducing alcohol—can all improve erectile function and may reduce your need for medication in the long term [1][2].

How Cured Pharmacy can help

Cured Pharmacy is a GPhC-registered online pharmacy offering a confidential consultation service for erectile dysfunction treatments. After you complete an online health questionnaire, a UK-registered prescriber will review your answers—including all your current medicines, such as alfuzosin—and decide whether sildenafil or another ED treatment is safe and suitable for you. If approved, your medicine is dispensed by our pharmacy team and delivered discreetly to your door. You can choose from a range of treatments, including generic sildenafil from £0.45 per tablet, with a first-order discount available using code Ednew.

When to get urgent help

• Chest pain during or after sex—call 999 and do not take nitrate medicines
• Erection lasting longer than 4 hours (priapism)—go to A&E immediately
• Sudden loss of vision or hearing—seek urgent medical attention
• Fainting or severe dizziness that doesn't improve—contact your GP or call 111
• Severe allergic reaction (swelling of face, lips, or throat, difficulty breathing)—call 999

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