Side Effects of Sildenafil and How to Reduce Them

The most common sildenafil side effect is a headache, which may affect more than 1 in 10 men who take this medication. However, most headaches go away after the first week.

Common side effects of sildenafil affect up to 1 in 10 people. These include:

• visual disturbances and changes in colour perception
• flushed skin and/or facial flushing
• stuffy nose
• indigestion
• nausea (feeling sick)
• dizziness

Uncommon and rare side effects

Uncommon sildenafil side effects affect up to 1 in 100 people. They include:

• sleepiness
• decreased touch sensitivity
• problems with the eyes
• dizziness (vertigo)
• ringing in the ears (tinnitus)
• dry mouth
• vomiting (being sick)
• heartburn
• muscle aches
• blood in the urine
• chest pain
• increased heart rate
• pounding heartbeat
• feeling hot
• pain in the arms or legs
• upper abdominal pain
• high or low blood pressure
• blocked or stuffy sinuses
• inflammation of the lining of the nose (symptoms include runny nose, sneezing and stuffy nose)
• nosebleed

There are also very rare sildenafil tablet side effects, which can affect up to 1 in 1,000 people. If you notice symptoms of any of the following, it’s important that you call 999 in an emergency or speak to a doctor straight away:

• fainting
• stroke
• heart attack
• irregular heartbeat
• temporary decreased blood flow to parts of the brain
• feeling of tightening of the throat
• numb mouth
• bleeding at the back of the eye
• double vision
• reduced sharpness of vision
• abnormal sensation in the eye
• swelling of the eye or eyelid
• small particles or spots in your vision
• seeing halos around lights
• dilation of the pupil of the eye
• discolouration of the white of the eye
• penile bleeding
• presence of blood in semen
• dry nose and/or swelling of the inside of the nose
• feeling irritable
• a sudden decrease or loss of hearing

For further information and a complete list of the side effects of sildenafil, see the patient information leaflet.

Some health conditions could increase the side effects of sildenafil

If you’ve been diagnosed with moderate to severe liver or kidney dysfunction, this can make sildenafil side effects more likely. Your liver or kidney may remove sildenafil less quickly from your bloodstream. This means sildenafil may remain in the body for longer and in larger quantities.

If you’ve been diagnosed with any medical condition, always tell your doctor when they are prescribing sildenafil.

Food and other medication in your system can affect sildenafil side effects:

Other medications and sildenafil side effects

Taking sildenafil at the same time as some other medications could increase your risk of sildenafil side effects.

Before taking sildenafil, it is important to tell your doctor if you are taking any other medication. They can make sure sildenafil is safe to take with your other medications. If your medications change whilst taking sildenafil, let your doctor know. If you get sildenafil side effects that do not go away or bother you whilst you are taking sildenafil for ED, stop taking the medication and speak to your doctor.

Some drugs, such as ritonavir (used to treat HIV infection) mean that sildenafil stays in the body for longer. This may increase the chances of you experiencing side effects.

Sildenafil must not be taken at the same time as nitrates (for example, nitroglycerin spray, or ‘poppers’) as this can lead to life-threatening drops in blood pressure. For similar reasons, you must also be careful if you take alpha-blockers such as tamsulosin.

For more detailed information on what not to take when taking sildenafil, more guidance is available in the patient information leaflet.

Can sildenafil react with food?

Yes. Sildenafil can interact with food, specifically:

• grapefruit juice - you should not have grapefruit juice with sildenafil as it stops the enzyme that breaks sildenafil down in your body from working
• heavy, large meals – you can take sildenafil with or without food, but a heavy meal can delay its effect
• alcohol – this can stop you from getting an erection and lower your blood pressure, increasing the chance of getting side effects

To reduce the risk of side effects when taking sildenafil, you should:

• speak to your doctor before taking it if you use any other medications, especially certain medications for low blood pressure
• drink plenty of water before taking sildenafil, especially if you have ever felt faint or dizzy while taking it in the past – dehydration can worsen these side effects
• avoid or limit your alcohol intake, as this can worsen or cause side effects like headaches or dizziness
• take over the counter painkillers like paracetamol if you get a headache after taking sildenafil
• only take as much sildenafil as you have been prescribed, since taking more will increase the risk of side effects

You need to be sexually aroused for sildenafil to work. You can increase the chances of it working on your current dose by understanding how to get an erection. If you think you need a higher dose to maintain your erection, speak to your doctor.

Most sildenafil side effects do not last long and are mild. They usually go away once you stop taking the medication. When taking sildenafil for ED, you should only be using the medication for sexual activity (and maximum once per day). This means you are unlikely to get sildenafil side effects long-term.

In rare cases, some side effects could last long term. For example, if you get a prolonged erection that does not go away after 4 hours, this could make your erectile dysfunction worse. You should get medical attention straight away if this happens.

Sildenafil and vision

Sildenafil can also cause vision problems but this is rare. This could lead to permanent or long-term changes to your vision. Visual side effects of sildenafil are reported by 3 to 11% of men taking between 25mg and 100mg doses (100mg is the maximum dose permitted in the UK). Research shows that visual problems are much more likely to affect men who take too much sildenafil. Half of men taking 200mg get visual disturbances, and 100% of people taking 600 to 800mg get them. This is why you must never take more sildenafil than you have been prescribed.

If you are worried about any long-term sildenafil side effects, speak to your doctor.

➤ Find out more about the different doses of sildenafil.

No, research has shown that the chances of getting side effects when taking sildenafil for ED specifically are small. A large study including 979 men taking sildenafil over a prolonged period of 4 years found that:

• only 37 (3.8%) experienced one or more side effects
• the vast majority (over 96%) experienced no unwanted sildenafil side effects at all

Yes, sildenafil is an effective and safe treatment for ED for most men. However, some medical conditions and medications could make sildenafil unsafe. In these cases, you may be offered another treatment.

When ordering sildenafil through our website, you will be asked to complete a brief medical questionnaire. This will be checked by a doctor, to make sure it is safe and appropriate for you.

No, research shows that sildenafil has a good safety profile in men with ED and cardiovascular disease. Although it can cause temporary side effects on the heart, such as a rapid heartbeat, this is a short-term side effect. In most cases of significant heart problems in men taking sildenafil, they already had a condition that affected their heart.

Sildenafil, like other ED medication, can cause a small, temporary drop in blood pressure. This isn’t ‘hard’ on the heart, but could be an issue for men who have certain cardiovascular diseases. If you’ve ever had heart health problems (such as heart attack, or angina) or blood pressure problems, tell your doctor before taking sildenafil.

Like any medication, there are some serious sildenafil side effects. It is rare to get serious side effects, but you should go to A&E or call 999 straight away if you get:

• a severe allergic reaction, which includes symptoms such as breathing difficulties, dizziness, and swelling in the face or mouth
• symptoms of a heart attack, such as pain in the chest, sweating, and dizziness
• symptoms of a stroke, such as sudden numbness, confusion, and trouble speaking
• chest pains – sit down and try to relax, this should go away but if not speak to a doctor straight away
• bleeding from the penis
• a prolonged erection (more than 4 hours)
• a serious skin reaction, which could cause skin peeling, blistering, and swelling
• seizures (fits)
• a sudden loss or serious decrease in vision

These side effects may be more likely if you already have a medical condition. Our doctors will make sure that sildenafil is safe for you to take before they prescribe it. You should only take sildenafil as it has been prescribed to you. Only a doctor can increase your dose.

There are no erectile dysfunction treatments that have no side effects. There may be another treatment that is more suitable for you if you have a medical condition or take a certain medication. ZAVA can prescribe a range of other erectile dysfunction treatments.

If you are not sure which ED treatment to choose, you can get an erectile dysfunction trial pack. This means you can try 3 different treatments to see which one works best for your ED and which gives you the least side effects. If you are not sure which ED treatment is best for you, speak to a doctor for free through your online account.