Is Sildenafil Safe, and What to Know About Drinking Alcohol

Sildenafil is a licensed UK medicine with a well documented safety profile, and for most people who are assessed as suitable it is safe. The word doing the work in that sentence is assessed. Safety is not something the tablet carries by itself. It comes from the fit between the medicine and the person taking it, which is why the same tablet is routine for one man and excluded for another.

That is why this page spends more time on who should not take it than on reassurance. There is a short list of absolute exclusions where the risk is serious and immediate, a longer list of conditions that need checking rather than ruling anyone out, and one interaction that can be fatal.

On alcohol, there is a specific documented finding that almost no page quotes. Sildenafil at the standard strength did not worsen the blood-pressure-lowering effect of alcohol in healthy volunteers with mean maximum blood alcohol levels of 80mg per dl. That is a real study with a real number, and it answers the question people are actually asking far better than a vague warning to drink sensibly.

Key things to know

• Nitrates and nitric oxide donors are an absolute exclusion. The combination can cause a dangerous fall in blood pressure. This includes amyl nitrite, sometimes called poppers
• Alcohol did not worsen sildenafil's blood pressure effect in a study at mean maximum blood alcohol levels of 80mg per dl
• Heavy drinking works against you anyway. Drinking excessive alcohol can temporarily reduce a man's ability to get an erection
• Most blood pressure tablets are not a barrier. Diuretics, beta blockers, ACE inhibitors and angiotensin II antagonists showed no difference in side effect profile compared with placebo
• Alpha blockers are the exception among blood pressure medicines and need specific attention
• Sildenafil is not suitable for anyone with low blood pressure, or high blood pressure that is not controlled
• Headache is the only very common side effect, affecting more than 1 in 10 people
• Treatment suitability depends on an individual clinical assessment

Is Sildenafil Safe?

Is It Safe for Most People?

Yes, for people assessed as suitable. Sildenafil has been licensed in the UK for many years, its safety and effectiveness were maintained in long-term studies, and in controlled clinical trials the discontinuation rate was low and similar to placebo.

That last figure is the most useful measure of tolerability there is. People taking the real medicine stopped because of side effects at about the same rate as people taking a dummy tablet.

The side effects that do occur are mostly predictable and mild. Headache sits alone in the very common band, reported by more than 1 in 10 people. Nausea, indigestion, a stuffy nose, dizziness, facial flushing, hot flush, a colour tinge to vision, blurred vision and visual disturbance are common, affecting up to 1 in 10.

None of that makes it safe for everybody. The exclusions below are not cautious hedging. They are specific and they matter.

Safety Checks Before Taking It

These are the checks a proper assessment covers, and the ones worth running through yourself beforehand.

1. Nitrates. Any medicine for angina or chest pain, in tablet, spray or patch form. This is an absolute exclusion
2. Riociguat, used for high blood pressure in the lungs. Also an absolute exclusion
3. Blood pressure. Both low blood pressure and uncontrolled high blood pressure are exclusions
4. Recent cardiac events. A heart attack or stroke within the last 6 months, unstable angina or severe cardiac failure
5. Eye history. Previous loss of vision from damage to the optic nerve, or an inherited eye disease such as retinitis pigmentosa
6. Liver. A severe liver problem is an exclusion
7. Other medicines, particularly alpha blockers and medicines that affect liver enzymes
8. Allergy to sildenafil or any of the other ingredients

Safety for First-Time Users

The single most important thing before a first tablet is an honest account of your medical history and every medicine you take, including anything bought without a prescription.

Two things commonly get left out at a first consultation, and both matter. The first is medicines taken occasionally rather than daily, particularly anything for chest pain. The second is recreational substances, for the same reason.

What to expect the first time is also worth knowing, because it prevents unnecessary alarm. A headache or a flushed face is common and not a sign that something has gone wrong, and a colour tinge to vision is common and passes. Chest pain, a sudden decrease or loss of vision, an allergic reaction, or an erection lasting longer than 4 hours are not in that category and need immediate medical attention.

One more point that surprises first-time users: in the reviewed studies, some men only reported improvement after several doses, up to eight. A single disappointing first attempt is weak evidence.

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Who Should Avoid Sildenafil

Contraindications

These are the documented exclusions. They are not preferences, and they are not negotiable at a consultation.

Sildenafil should not be taken by anyone who:

• Takes any medicine called a nitrate or a nitric oxide donor
• Takes riociguat, used to treat high blood pressure in the lungs
• Takes ritonavir
• Is allergic to sildenafil or any of the other ingredients
• Has been advised to avoid activity that strains the heart because of a heart or blood vessel problem, such as a heart attack or stroke within the last 6 months, unstable angina or severe cardiac failure
• Has ever had loss of vision because of damage to the optic nerve, or has an inherited eye disease such as retinitis pigmentosa
• Has low blood pressure, or high blood pressure that is not controlled
• Has a severe liver problem
• Has a disease or deformity affecting the penis, such as Peyronie's disease

Sildenafil is licensed for adult men aged 18 and over, and is not indicated for women.

Our guide to what to avoid when taking sildenafil covers the day-to-day cautions that sit below this list.

The Nitrates Warning

This is the most serious interaction associated with sildenafil, and it is the reason the assessment exists.

Nitrates and nitric oxide donors are used mainly for angina and chest pain. Taking them with sildenafil may lead to a dangerous fall in blood pressure, which can cause fainting or worse. This is an absolute exclusion rather than a caution, and no strength, timing or spacing makes it acceptable.

Nitrates appear in more forms than people expect:

• Glyceryl trinitrate, as tablets, a spray or a patch
• Isosorbide mononitrate and isosorbide dinitrate
• Nicorandil
• Amyl nitrite

If you have ever been given something to put under your tongue for chest pain, that is very likely a nitrate. Say so at the consultation, even if you use it rarely. A medicine used once a month is still a medicine.

Recreational Drugs

The specific and serious concern here is amyl nitrite, sometimes sold as poppers. It is a nitrite, and use with sildenafil is contraindicated in the product information.

The mechanism is the same as for prescribed nitrates. Both amyl nitrite and sildenafil widen blood vessels and lower blood pressure. Together, that can produce a drop severe enough to be life-threatening.

This is not a general caution about recreational substances. It is a specific, documented, potentially fatal combination, and it is worth being direct about, because people who use amyl nitrite often do not think of it as a medicine and do not mention it. It needs to be disclosed, and a consultation is confidential.

Other substances are not individually documented in the reviewed material, but anything that affects blood pressure or heart rate belongs in the same conversation. Our sildenafil interactions guide covers the prescribed medicines in more detail.

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Sildenafil With Alcohol

Does Alcohol Stop Sildenafil Working?

Not directly, but heavy drinking can stop you working, which looks identical from the outside.

The documented statement is precise: drinking excessive alcohol can temporarily reduce a man's ability to get an erection. That describes alcohol acting on your own response, not alcohol disabling the medicine or clearing it from your system faster.

The distinction matters because the two problems have different solutions. If alcohol is the reason an evening did not go as expected, the answer is less alcohol. It is not a stronger tablet, and the product information does not support treating it as a dosing problem.

How Much Alcohol Can You Drink?

There is one documented study, and it gives a specific number. Sildenafil at the standard strength did not worsen the blood-pressure-lowering effect of alcohol in healthy volunteers with mean maximum blood alcohol levels of 80mg per dl.

What that study shows is meaningful and also limited. It shows that at around that blood alcohol level, sildenafil did not make alcohol's blood-pressure-lowering effect worse. Both alcohol and sildenafil lower blood pressure a little on their own, and the concern was that together they might do so more than expected. In healthy volunteers at that level, they did not.

What it does not show is equally important. It was conducted in healthy volunteers, not in people with heart conditions or on blood pressure medicines. It tested one strength. It did not test heavier drinking.

So it is not a green light for drinking as much as you like, and the reviewed product information does not publish a recommended number of units to stay under. UK guidance on alcohol generally advises no more than 14 units a week, which is a sensible reference point rather than a sildenafil-specific limit.

Sildenafil With Beer or Wine

The product information does not distinguish between drink types, and there is a good reason for that.

What the study measured was blood alcohol level, not what was drunk to produce it. Beer, wine and spirits are simply different routes to the same blood alcohol concentration. Two pints of ordinary strength beer and two large glasses of wine are broadly similar in alcohol content, and the body does not care which container it arrived in.

So there is no separate answer for beer or wine. The relevant question is how much alcohol in total, not which drink.

One practical note that is documented and often overlooked in this context. The instruction not to take sildenafil with grapefruit or grapefruit juice is about grapefruit specifically, not about drinks generally.

Heavy Drinking Risks

Heavy drinking is where the picture genuinely changes, and it changes for three separate reasons.

The third row is the one nobody writes about and the one that concerns clinicians most. Sildenafil's serious warnings depend on you noticing a symptom and acting on it. Chest pain during or after use is an emergency, and someone heavily intoxicated is less likely to identify that as a warning sign and less likely to seek help promptly.

There is no documented safe upper limit for alcohol with sildenafil, and this page will not invent one. What the evidence supports is that moderate intake around the level studied did not worsen the blood pressure effect, and that excessive intake undermines the response and blunts your ability to recognise a problem.

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Sildenafil With Existing Conditions

Is It Safe With High Blood Pressure?

It depends entirely on whether the high blood pressure is controlled.

High blood pressure that is not controlled is a documented exclusion, and low blood pressure is also an exclusion.

High blood pressure that is well controlled on treatment is a different situation and is not automatically a barrier. What matters is the current reading and which medicines are producing it, which is exactly what an assessment establishes.

Sildenafil lowers blood pressure slightly in everyone. The mean maximum decrease in supine systolic blood pressure at the highest strength was 8.4 mmHg, with a corresponding diastolic change of 5.5 mmHg. For most people that is unremarkable. For someone already close to the low end, it is not.

Can You Take It With Blood Pressure Tablets?

For the most commonly prescribed classes, the documented answer is reassuring and specific.

Pooling of diuretics, beta blockers, ACE inhibitors and angiotensin II antagonists showed no difference in the side effect profile in patients taking sildenafil compared with placebo. That is a direct finding, and it covers the majority of people on blood pressure medication.

Alpha blockers are the exception, and they need naming.

Alpha blockers include doxazosin, tamsulosin and alfuzosin, and they are often prescribed for prostate symptoms as well as blood pressure. When sildenafil and doxazosin were given simultaneously to patients already stabilised on doxazosin, mean additional reductions in supine blood pressure of 7/7 mmHg, 9/5 mmHg and 8/4 mmHg were recorded.

That does not mean the combination is forbidden. It means it needs a prescriber who knows about it. Your prescriber will determine the appropriate treatment.

Is It Safe With Heart Disease?

This is the area where the answer genuinely splits, and a vague reassurance would be the wrong thing to give.

Sildenafil is excluded for people with severe cardiovascular disorders. That includes a heart attack or stroke within the last 6 months, unstable angina, and severe cardiac failure. It is also excluded for anyone advised to avoid activity that strains the heart because of a heart or blood vessel problem.

Stable, well managed heart disease is a different question, and it is a clinical judgement rather than an automatic no. The critical issue for most people with cardiac history is not the heart condition itself but the medicines that come with it, because nitrates are so commonly prescribed for angina.

Chest pain during or after use is an emergency and needs immediate medical attention. This medicine should only be used under the supervision of an appropriately qualified prescriber.

Is It Safe With Diabetes?

Diabetes is not an exclusion, and sildenafil is used by people with diabetes. What the evidence adds is a realistic expectation of how well it works.

Across all trials, the proportion of patients reporting improvement was 59% among those with diabetes, compared with 84% among those whose difficulty had a psychological cause.

Sildenafil was therefore associated with improvement in a substantial proportion of men with diabetes, although response rates were lower than in some other groups.

Diabetes also brings a higher likelihood of the cardiovascular conditions and medicines that do matter, which is another reason the assessment covers the whole picture rather than the diagnosis alone. Results vary between individuals.

How to Reduce Side Effects

The most common side effects are related to how the medicine works, so they cannot be eliminated. Several practical factors are documented and within your control.

Two things are worth saying plainly. Never take a second tablet because the first seemed weak, and never take two tablets of a lower strength to make up a higher one. If side effects are troublesome, that is a conversation with a prescriber rather than something to manage by adjusting the dose yourself.

Does Sildenafil Have Long-Term Side Effects?

No cumulative long-term damage is documented. The safety and effectiveness of sildenafil were maintained in long-term studies, and effectiveness and satisfaction with treatment is maintained at one year and longer.

There is also no indication from controlled clinical trial or post-marketing data that patients develop dependence or addiction, and tolerance is not documented.

The serious events that appear in the documentation, including non-arteritic anterior ischaemic optic neuropathy and sudden decrease or loss of hearing, are rare acute events rather than progressive damage. Our guide to sildenafil long-term use covers this in more detail.

Red Flags: When to Stop and Seek Help

Stop taking sildenafil and seek medical attention immediately for any of the following:

• Chest pain, during or after use. This is an emergency
• An erection lasting longer than 4 hours. Persistent and sometimes painful, known as priapism. It needs urgent treatment rather than waiting
• A sudden decrease or loss of vision, in one or both eyes
• A sudden decrease or loss of hearing
• An allergic reaction, including rash, swelling of the face, lips or throat, or difficulty breathing
• Fainting or collapse

Suspected side effects can be reported through the MHRA Yellow Card scheme.

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