Sildenafil, widely known as Viagra, is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK for erectile dysfunction and pulmonary arterial hypertension. Whilst its primary role is well-established, questions often arise about whether sildenafil is good for prostate health, particularly as erectile dysfunction and lower urinary tract symptoms frequently coexist in men. This article examines the evidence surrounding sildenafil's potential effects on prostate-related conditions, clarifies its licensed indications, and explains when to seek medical advice for prostate symptoms.

What Is Sildenafil and How Does It Work?

Sildenafil is a medication licensed in the UK for the treatment of erectile dysfunction (ED) and pulmonary arterial hypertension. It belongs to a class of drugs known as phosphodiesterase type 5 (PDE5) inhibitors. The medication is widely recognised under the brand name Viagra, though generic versions are now commonly available. Viagra Connect (50 mg) is also available as a pharmacy medicine following assessment by a pharmacist, while other strengths remain prescription-only.

The mechanism of action centres on the inhibition of the PDE5 enzyme, which is found in high concentrations in the smooth muscle of the corpus cavernosum of the penis, as well as in pulmonary vasculature and other tissues. When sexual stimulation occurs, nitric oxide is released in the erectile tissue, activating an enzyme called guanylate cyclase. This increases levels of cyclic guanosine monophosphate (cGMP), which relaxes smooth muscle and allows increased blood flow into the penis, facilitating an erection.

Sildenafil works by preventing the breakdown of cGMP by PDE5, thereby prolonging smooth muscle relaxation and enhancing erectile function. It is important to note that sildenafil does not cause an erection on its own—sexual stimulation is required for the medication to be effective. The drug is typically taken approximately one hour before sexual activity, with effects lasting up to four to five hours. A high-fat meal may delay the onset of action.

In the UK, sildenafil is available in doses of 25 mg, 50 mg, and 100 mg tablets. The usual starting dose is 50 mg, which can be adjusted to 25-100 mg based on effectiveness and tolerability. It should not be taken more than once daily. While its primary indication is erectile dysfunction, research has explored its potential effects on other conditions, including those related to prostate health.

Safety Considerations and When to Speak With Your GP

Sildenafil is generally well-tolerated, but like all medications, it carries potential risks and is not suitable for everyone. Common adverse effects include headache, facial flushing, indigestion, nasal congestion, and visual disturbances (such as a blue tinge to vision or increased sensitivity to light). These effects are usually mild and transient, resolving without intervention.

More serious but rare adverse effects include sudden vision loss (non-arteritic anterior ischaemic optic neuropathy), sudden hearing loss, and priapism (a prolonged, painful erection lasting more than four hours). Priapism is a medical emergency requiring immediate treatment to prevent permanent damage to penile tissue. If you experience an erection lasting longer than four hours, you should attend A&E immediately.

Contraindications are particularly important. Sildenafil must never be taken with nitrate medications (such as glyceryl trinitrate used for angina), nicorandil, or nitric oxide donors (including 'poppers' or amyl nitrite). These combinations can cause a dangerous drop in blood pressure. Concomitant use with riociguat is also contraindicated. Sildenafil should be used with caution in men with severe cardiovascular disease, recent stroke or myocardial infarction, hypotension, severe hepatic impairment, retinal disorders including retinitis pigmentosa, or previous non-arteritic anterior ischaemic optic neuropathy.

If you are taking alpha-blockers (e.g., tamsulosin, doxazosin), ensure you are stable on this treatment before starting sildenafil, which should be initiated at the lowest dose (25 mg). Be aware that certain medicines (including ritonavir, erythromycin, ketoconazole) and grapefruit juice can increase sildenafil levels.

Before starting sildenafil, you should discuss your full medical history with your GP, including:

• Current medications (including over-the-counter and herbal products)

• History of cardiovascular disease, stroke, or blood pressure problems

• Liver or kidney disease

• Blood disorders such as sickle cell anaemia or leukaemia

• Anatomical deformity of the penis or bleeding disorders

• History of priapism

You should seek urgent medical attention if you experience chest pain during or after sexual activity (call 999 if severe or ongoing) and do not use nitrate medications. For sudden vision or hearing changes, stop taking sildenafil and seek same-day medical assessment. For other concerns or if the medication is not effective, contact your GP. Regular medication reviews are important, particularly if you have multiple health conditions or take other prescription drugs.

If you experience any suspected side effects, you can report them via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Sildenafil and Prostate Health: What the Evidence Shows

The relationship between sildenafil and prostate health has been the subject of clinical research, though it is important to emphasise that sildenafil is not licensed in the UK for the treatment of prostate conditions. The prostate gland, which surrounds the urethra below the bladder, commonly enlarges with age—a condition known as benign prostatic hyperplasia (BPH)—and can contribute to lower urinary tract symptoms (LUTS).

PDE5 enzymes are present not only in penile tissue but also in the prostate, bladder, and urethra. This has led researchers to investigate whether PDE5 inhibitors like sildenafil might have beneficial effects on prostate-related symptoms. Some laboratory studies have suggested that PDE5 inhibitors may help relax smooth muscle in the prostate and bladder neck, potentially improving urinary flow.

However, there is no official link established between sildenafil use and direct improvement in prostate health or reduction in prostate size. Clinical trials have produced mixed results. Some studies have shown modest improvements in urinary symptoms when sildenafil is used alongside standard BPH treatments (such as alpha-blockers), whilst others have found no significant benefit.

It is worth noting that while sildenafil is not licensed for LUTS/BPH, another PDE5 inhibitor, tadalafil (5 mg daily), is licensed in the UK for this indication. This distinction is important when considering treatment options.

It is also worth noting that erectile dysfunction and lower urinary tract symptoms often coexist, particularly in older men. Both conditions share common risk factors including age, diabetes, cardiovascular disease, and metabolic syndrome. Therefore, whilst sildenafil may improve erectile function in men who also have prostate-related urinary symptoms, any perceived improvement in urinary symptoms may be indirect or related to improved quality of life rather than a direct pharmacological effect on the prostate itself.

If you are taking sildenafil for erectile dysfunction and alpha-blockers for BPH, be aware of the potential for increased risk of hypotension (low blood pressure) when these medications are combined.

Current NICE guidance does not recommend sildenafil as a treatment for BPH or LUTS. Men experiencing prostate symptoms should be assessed and managed according to established clinical pathways, which typically involve alpha-blockers (such as tamsulosin) or 5-alpha reductase inhibitors (such as finasteride) as first-line pharmacological treatments.

Can Sildenafil Help With Prostate-Related Urinary Symptoms?

Whilst some research has explored the potential of sildenafil for lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia, the evidence remains inconclusive and insufficient to support its routine use for this indication in UK clinical practice. Sildenafil is not licensed or recommended for LUTS/BPH, although tadalafil 5 mg daily (another PDE5 inhibitor) is licensed for this purpose in the UK.

Some clinical trials have suggested that daily low-dose sildenafil (typically 25 mg) may produce modest improvements in urinary symptom scores, particularly in men who also have erectile dysfunction. The proposed mechanism involves relaxation of smooth muscle in the prostate, bladder neck, and urethra through increased cGMP levels. However, these improvements have generally been small and not consistently replicated across studies.

A key consideration is that sildenafil is not a substitute for established BPH treatments. Men with bothersome urinary symptoms should undergo proper assessment, which typically includes:

• Detailed history of urinary symptoms

• International Prostate Symptom Score (IPSS) questionnaire

• Physical examination including digital rectal examination (DRE) and external genitalia

• Urinalysis to exclude infection or blood in urine

• Prostate-specific antigen (PSA) blood test after discussion of benefits, risks and limitations

Specialist assessment may include urine flow rate testing (uroflowmetry) and post-void residual volume measurement.

It's important to be aware of red flag symptoms that require urgent referral: suspicious findings on DRE, raised PSA (after repeat testing), visible blood in urine, recurrent urinary tract infections, urinary retention, bone pain or unexplained weight loss.

First-line management typically involves lifestyle modifications (reducing caffeine and alcohol, timed voiding, bladder training) and, if needed, alpha-blocker medications such as tamsulosin or alfuzosin for voiding symptoms. For men with enlarged prostates or at high risk of progression, 5-alpha reductase inhibitors may be appropriate, sometimes in combination with alpha-blockers. For storage symptoms (frequency, urgency), antimuscarinic medications or mirabegron might be considered.

If you are taking sildenafil for erectile dysfunction and also have prostate-related urinary symptoms, it is important to discuss both conditions with your GP. They can ensure you receive appropriate investigation and evidence-based treatment for your urinary symptoms, whilst safely managing your erectile dysfunction. If you are prescribed both sildenafil and an alpha-blocker, be aware of the potential for increased risk of low blood pressure. Do not take sildenafil specifically for prostate symptoms without medical advice, as this is an off-label use without sufficient supporting evidence, and other treatments are more appropriate and effective for this indication.

Frequently Asked Questions