Sildenafil and Silodosin: Can They Be Taken Together?

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Key takeaways

• Sildenafil and silodosin can be taken together under medical supervision, but both lower blood pressure.
• You must be stable on silodosin before starting sildenafil at the lowest dose to reduce dizziness risk.
• Stand up slowly and sit down if you feel dizzy; avoid heavy alcohol and grapefruit juice.
• Declare all your medicines during your consultation; never take sildenafil with nitrates or poppers.
• Seek urgent help for chest pain, an erection lasting over four hours, or sudden vision or hearing loss.

What is sildenafil and silodosin used for?

Sildenafil (also known as Viagra) is a prescription medicine used to treat erectile dysfunction in men [3]. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Sildenafil is usually taken about one hour before sexual activity, and its effects can last for up to four hours. Common doses are 25mg, 50mg, and 100mg, and you should not take it more than once a day [3].

Silodosin is an alpha-blocker prescribed to relieve urinary symptoms associated with benign prostatic hyperplasia (BPH), or an enlarged prostate [12]. It works by relaxing the muscles in the prostate and bladder neck, making it easier to pass urine. Silodosin is usually taken once daily. Many men with BPH also experience erectile dysfunction, so it is not uncommon for both conditions to be treated at the same time. However, because both medicines affect blood pressure, combining them requires careful assessment by your doctor or prescriber.

How do sildenafil and silodosin interact?

Both sildenafil and silodosin can lower blood pressure, and when taken together, this effect may be more pronounced. Sildenafil relaxes blood vessels throughout the body, including those that supply the penis, which can lead to a modest drop in blood pressure [3]. Silodosin, as an alpha-blocker, also relaxes smooth muscle in blood vessels, particularly those in the prostate and bladder neck, but this relaxation can affect overall blood pressure too.

When the two medicines are combined, there is an increased risk of symptomatic low blood pressure (hypotension). This may cause dizziness, light-headedness, fainting, or a feeling of weakness, particularly when you stand up quickly (a condition known as postural or orthostatic hypotension). The risk is highest when you first start treatment, when doses are increased, or if you are also taking other medicines that lower blood pressure. This interaction is well recognised, and prescribers are trained to manage it by ensuring you are stable on your alpha-blocker before introducing sildenafil at the lowest effective dose.

The mechanism in plain English

Think of your blood vessels as flexible tubes that can widen or narrow. Silodosin tells the muscles around certain blood vessels (especially near the prostate) to relax and widen, which helps urine flow more easily. Sildenafil does something similar, but mainly in the blood vessels of the penis, helping blood flow in during sexual arousal. When both medicines are working at the same time, more blood vessels relax across your body, which can lower your overall blood pressure. If your blood pressure drops too much, you may feel dizzy or faint, especially when you stand up, because your body needs a moment to adjust the blood flow to your brain.

At a glance

What does your prescriber check before combining sildenafil and silodosin?

Before prescribing sildenafil to someone already taking silodosin, a UK prescriber will carry out a thorough assessment to ensure the combination is safe for you. They will ask about your current dose of silodosin, how long you have been taking it, and whether you have experienced any side effects such as dizziness or fainting. It is important that you are stable on your alpha-blocker therapy before starting a PDE5 inhibitor [3].

Your prescriber will also review your blood pressure, any history of heart or circulation problems, and all other medicines you are taking. They will check for contraindications, such as the use of nitrates (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational drugs known as 'poppers' (amyl or alkyl nitrites), because these must never be taken with sildenafil due to the risk of a dangerous drop in blood pressure. If you are taking other blood-pressure-lowering medicines, such as ACE inhibitors, beta-blockers, or calcium-channel blockers, your prescriber will consider the cumulative effect on your blood pressure.

If the combination is deemed appropriate, you will usually be started on the lowest dose of sildenafil (typically 25mg) to minimise the risk of side effects. Your prescriber may advise you to take sildenafil at a different time of day from silodosin, or to sit or lie down if you feel dizzy. You should never increase the dose of either medicine on your own, and you should report any new symptoms, such as persistent dizziness, fainting, or chest pain, to your doctor or pharmacist immediately.

Practical advice when taking sildenafil and silodosin together

If your prescriber has confirmed that it is safe for you to take sildenafil and silodosin together, there are several practical steps you can take to reduce the risk of side effects. First, always take each medicine exactly as prescribed. Do not take more sildenafil than recommended, and do not take it more than once in 24 hours. Sildenafil is usually taken about one hour before sexual activity, on an empty stomach or after a light meal, as a heavy or high-fat meal can delay its effect [3].

Be mindful of how you feel when you stand up, especially in the first few hours after taking sildenafil. If you feel dizzy or light-headed, sit or lie down until the feeling passes, and stand up slowly from a sitting or lying position. Avoid drinking large amounts of alcohol, as this can make low blood pressure worse and also impair your ability to get an erection. Grapefruit juice may increase the levels of sildenafil in your blood, so it is best to avoid it while using this medicine.

Keep a list of all your medicines, including over-the-counter products and supplements, and share it with every healthcare professional you see. If you are prescribed a new medicine, always tell the prescriber that you are taking both sildenafil and silodosin. If you experience severe dizziness, fainting, chest pain during sex, or an erection that lasts longer than four hours, seek urgent medical help. At Cured Pharmacy, our UK-registered prescribers review every consultation to ensure that sildenafil is safe and suitable for you, taking into account all your current medicines and health conditions.

Tips to minimise dizziness

Stay well hydrated, but avoid excessive alcohol. When getting out of bed or standing up from a chair, do so slowly: sit on the edge of the bed for a moment before standing, and hold onto something stable if needed. If you feel dizzy, sit down immediately and lower your head between your knees, or lie down with your legs raised. These simple measures can help prevent falls and injury. If dizziness persists or worsens, contact your GP or prescriber for advice.

Are there alternatives to sildenafil if you take silodosin?

If you are taking silodosin and are concerned about the interaction with sildenafil, it is worth knowing that all PDE5 inhibitors (the class of medicines used for erectile dysfunction) have a similar interaction with alpha-blockers. This includes tadalafil (Cialis), vardenafil (Levitra), and avanafil (Spedra) [4][5][6]. The same precautions apply: you should be stable on your alpha-blocker, and your prescriber will start you on the lowest dose of the PDE5 inhibitor.

Some men find that tadalafil, which has a longer duration of action (up to 36 hours), offers more flexibility and may be easier to fit around their daily routine. Tadalafil is also available as a low-dose daily tablet (2.5mg or 5mg), which means you do not need to time it around sexual activity [4]. However, the interaction with silodosin is still present, and the same blood-pressure precautions apply. Avanafil (Spedra) works more quickly than sildenafil (as soon as 15–30 minutes) and may be preferred by some men, but again, the interaction with alpha-blockers must be managed carefully [6].

If PDE5 inhibitors are not suitable or effective for you, there are other treatments for erectile dysfunction, such as vacuum erection devices, alprostadil (available as a cream called Vitaros or an injection called Caverject), or in some cases, referral to a specialist for further assessment [2][7]. Your GP or a specialist can discuss these options with you. It is important not to stop taking silodosin without medical advice, as this may worsen your urinary symptoms. Always discuss any concerns about your treatment with a healthcare professional.

Warning signs and when to seek help with sildenafil and silodosin

Most men who take sildenafil and silodosin together do so safely, but it is important to be aware of warning signs that may indicate a problem. Seek urgent medical help (call 999 or go to A&E) if you experience severe chest pain during or after sex, as this could be a sign of a heart problem. Do not take another dose of sildenafil, and do not use GTN or any nitrate medicine if you have taken sildenafil in the past 24 hours, as this can cause a life-threatening drop in blood pressure.

If you have an erection that lasts longer than four hours (a condition called priapism), seek emergency help immediately. Priapism is a medical emergency that can cause permanent damage to the penis if not treated promptly. Sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing (which may be accompanied by ringing in the ears or dizziness), are rare but serious side effects that require immediate medical attention [3].

If you experience severe or persistent dizziness, fainting, or feel very unwell after taking sildenafil and silodosin together, contact your GP or call NHS 111 for advice. Do not drive or operate machinery if you feel dizzy or light-headed. If you have any concerns about side effects or the safety of your treatment, you can also contact the prescribing team at Cured Pharmacy for guidance. We are here to support you and ensure your treatment is both safe and effective.

Common side effects to be aware of

Common side effects of sildenafil include headache, flushing (redness of the face), indigestion, and nasal congestion [3]. These are usually mild and short-lived. Silodosin can cause dizziness, a runny or blocked nose, and retrograde ejaculation (where semen enters the bladder instead of leaving the body during orgasm) [12]. When the two medicines are taken together, dizziness and light-headedness may be more noticeable. If side effects are troublesome or do not go away, speak to your prescriber, who may be able to adjust your dose or suggest an alternative treatment.

When to get urgent help

• Severe chest pain during or after sex (call 999; do not take nitrates if you have used sildenafil in the past 24 hours)
• An erection lasting longer than 4 hours (priapism) – go to A&E immediately to prevent permanent damage
• Sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing
• Severe dizziness, fainting, or feeling very unwell after taking both medicines together
• Allergic reaction: swelling of the face, lips, tongue or throat, difficulty breathing, or severe skin rash

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