Sildenafil, commonly known as Viagra, is a widely prescribed treatment for erectile dysfunction in the UK. Many men wonder whether it is safe to drink alcohol whilst taking this medication. Both sildenafil and alcohol affect blood pressure and circulation, which raises important questions about their combined use. Understanding how these substances interact can help you use sildenafil safely and effectively. This article examines the pharmacology of sildenafil, the risks of combining it with alcohol, safe drinking limits, and when to seek medical advice, all in line with current UK clinical guidance.

How Sildenafil Works in the Body

Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK for the treatment of erectile dysfunction (as Viagra and generic products) and pulmonary arterial hypertension (as Revatio). These are distinct indications with different formulations and dosing regimens, and products are not interchangeable. The medication works by selectively blocking the PDE5 enzyme, which is responsible for breaking down cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of blood vessels.

When sexual stimulation occurs, nitric oxide is released in the erectile tissue of the penis, triggering an increase in cGMP levels. This chemical messenger causes the smooth muscles in the penile arteries to relax, allowing increased blood flow into the corpus cavernosum and resulting in an erection. By inhibiting PDE5, sildenafil helps maintain elevated cGMP levels, thereby prolonging vasodilation and supporting erectile function.

Key pharmacological properties for erectile dysfunction include:

• Usual starting dose: 50 mg taken as needed, approximately one hour before sexual activity

• Dose range: 25–100 mg, adjusted according to response and tolerability

• Maximum frequency: Once daily

• Onset of action: Typically 30–60 minutes after oral administration; a high-fat meal can delay absorption and reduce peak effect

• Peak plasma concentration: Reached approximately one hour after dosing on an empty stomach

• Duration of effect: Up to 4–5 hours, though this varies between individuals

• Metabolism: Primarily hepatic, via the cytochrome P450 enzyme system (CYP3A4 and CYP2C9)

Dose adjustments may be necessary in older adults, and in those with hepatic or renal impairment; a lower starting dose of 25 mg is often recommended in these groups. It is important to understand that sildenafil does not cause spontaneous erections—sexual arousal is still required to initiate the physiological cascade that the medication supports. The drug's vasodilatory effects are not limited to the penis; sildenafil causes mild systemic vasodilation, which can lead to a modest reduction in blood pressure. This mechanism becomes particularly relevant when considering interactions with other substances that affect cardiovascular function, including alcohol.

Risks of Combining Sildenafil and Alcohol

Both sildenafil and alcohol are vasodilators, meaning they cause blood vessels to widen and can lower blood pressure. Clinical studies in the UK product information show that sildenafil 50 mg did not potentiate the hypotensive effects of alcohol at moderate blood alcohol levels in healthy volunteers. However, heavy or binge drinking increases the risk of dizziness, postural hypotension, and other adverse effects, and may counteract the benefits of sildenafil for erectile function.

Cardiovascular effects of combining sildenafil with excessive alcohol may include:

• Dizziness or light-headedness, particularly on standing (postural hypotension)

• Increased heart rate

• Flushing and warmth

• Headache (a common side effect of both substances)

• In rare cases, fainting or syncope

Excessive alcohol consumption can also impair erectile function independently. Alcohol is a central nervous system depressant that can reduce sexual arousal, delay orgasm, and make achieving or maintaining an erection more difficult—effectively counteracting the intended benefits of sildenafil. Chronic heavy drinking is associated with long-term erectile dysfunction through multiple mechanisms, including hormonal imbalances, nerve damage, and vascular disease.

Cognitive and judgement impairment from alcohol may lead to risky sexual behaviour or failure to recognise warning symptoms that require medical attention. Additionally, alcohol can exacerbate certain side effects of sildenafil, such as facial flushing, nasal congestion, and gastrointestinal upset.

Important interactions and contraindications:

• Nitrates: Sildenafil must never be taken with nitrate medicines (such as glyceryl trinitrate for angina) or recreational nitrates ('poppers'), as this combination can cause life-threatening hypotension.

• Riociguat: Co-administration with riociguat (a guanylate cyclase stimulator used for pulmonary hypertension) is contraindicated.

• Alpha-blockers: Patients taking alpha-blockers for prostate symptoms or hypertension are at increased risk of postural hypotension. Sildenafil should only be started once the patient is stable on alpha-blocker therapy, and a lower starting dose (25 mg) should be considered. Heavy alcohol intake further increases this risk.

There is no absolute prohibition on moderate alcohol consumption when taking sildenafil in otherwise healthy individuals. However, those with pre-existing cardiovascular conditions, those taking multiple medications, or those consuming large quantities of alcohol face substantially elevated risks. Always inform your GP or prescriber about all medications, supplements, and your typical alcohol consumption to ensure safe, effective treatment.

Safe Alcohol Limits When Taking Sildenafil

Current UK guidance from the Chief Medical Officers recommends that both men and women should not regularly drink more than 14 units of alcohol per week, spread over three or more days, to minimise health risks. When taking sildenafil, additional caution is warranted to reduce the risk of side effects and to maximise the medication's effectiveness.

Practical recommendations for patients taking sildenafil:

• Follow UK low-risk drinking guidelines; if you choose to drink alcohol when taking sildenafil, keep to small amounts

• Avoid binge drinking or consuming alcohol rapidly, particularly around the time you take the medication

• Be aware that heavy drinking can impair erectile function and reduce the benefit of sildenafil

• Stay well hydrated with water or non-alcoholic beverages

• Be alert to any unusual symptoms, especially dizziness or light-headedness on standing

One unit of alcohol equates to approximately 10 ml (8 g) of pure alcohol. This translates to:

• Half a pint (284 ml) of standard-strength lager or beer (3.6% ABV)

• A single 25 ml measure of spirits (40% ABV)

• A small (125 ml) glass of wine at 12% ABV contains approximately 1.5 units

Many people underestimate their alcohol consumption, particularly with larger wine glasses or higher-strength beverages now commonplace. The NHS provides an online alcohol units calculator to help you track your intake accurately.

Individual factors significantly influence safe limits. Older adults metabolise both alcohol and sildenafil more slowly, increasing the duration and intensity of effects; a lower starting dose of sildenafil (25 mg) is often recommended in this group. Those with liver or kidney impairment may require dose adjustments for sildenafil and should be particularly cautious with alcohol. Body weight, concurrent medications (especially alpha-blockers), and overall cardiovascular health all play important roles.

Patients should be honest with their GP or prescriber about their typical alcohol consumption. If you regularly exceed recommended limits or have concerns about alcohol use, this should be discussed before starting sildenafil. The medication remains effective without alcohol, and avoiding heavy drinking on occasions when you take sildenafil represents the safest approach for minimising potential side effects and maximising therapeutic benefit.

When to Seek Medical Advice

While sildenafil is generally well-tolerated, certain symptoms warrant prompt medical attention, particularly if alcohol has been consumed alongside the medication. Understanding when to seek help is crucial for patient safety.

Seek immediate medical attention (call 999 or attend A&E) if you experience:

• Chest pain or pressure, especially during or after sexual activity

• Severe dizziness, fainting, or loss of consciousness

• Priapism—a painful erection lasting more than four hours (this is a medical emergency requiring urgent treatment to prevent permanent damage)

• Sudden vision loss or significant visual disturbances

• Sudden hearing loss or severe tinnitus

• Severe allergic reaction (anaphylaxis): difficulty breathing, swelling of face or throat, severe rash

• If you have inadvertently taken sildenafil with nitrates or riociguat and develop symptoms

Contact your GP or NHS 111 for advice if you notice:

• Persistent or worsening side effects such as severe headache, flushing, or indigestion

• Palpitations or irregular heartbeat

• Unexplained shortness of breath

• Any concerning symptoms that do not resolve within a few hours

Routine review is appropriate when:

• Sildenafil is not producing the desired effect (your GP may need to adjust the dose or investigate underlying causes)

• You develop new medical conditions or start new medications

• You have concerns about alcohol consumption or its interaction with your treatment

• Side effects are affecting your quality of life, even if not severe

Patients with pre-existing cardiovascular disease, including angina, heart failure, or previous myocardial infarction, should have regular follow-up with their GP. NICE guidance (Clinical Knowledge Summary on Erectile Dysfunction) emphasises the importance of cardiovascular risk assessment before initiating treatment for erectile dysfunction.

Important safety reminders:

• Never take sildenafil if you are using nitrate medications (such as glyceryl trinitrate for angina) or recreational nitrates ('poppers'), as this combination can cause life-threatening hypotension.

• Do not take sildenafil if you are using riociguat for pulmonary hypertension.

• If you are taking alpha-blockers, ensure you are stable on this treatment before starting sildenafil, and discuss the appropriate starting dose with your prescriber. Avoid heavy alcohol intake, which increases the risk of postural hypotension.

• Always inform healthcare professionals about all medications and supplements you are taking, and be forthcoming about alcohol and recreational drug use to ensure safe, effective treatment.

Reporting side effects: If you experience any side effects, talk to your doctor, pharmacist, or nurse. This includes any possible side effects not listed in the patient information leaflet. You can also report side effects directly via the MHRA Yellow Card scheme at www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects, you can help provide more information on the safety of this medicine.

Frequently Asked Questions