Oral treatment for erectile dysfunction

What is it?

Erectile dysfunction (ED) is when you are unable to get or keep an erection suitable for sexual intercourse or another chosen sexual activity (see our factsheet ‘Erectile dysfunction’).

Oral treatment for ED is taken by mouth as a tablet. There are four oral treatments currently available: sildenafil (Viagra®), tadalafil (Cialis®), vardenafil (Levitra®) and avanafil (Spedra®). They belong to a group of medicines called phosphodiesterase (pronounced phos- pho- di- es- ter- ase) inhibitors (PDE5i).  These treatments should only be prescribed by a doctor who will take your health and other medications into account. Do not buy medicines online – they may be fakes!

How does it work?

PDE5i are not aphrodisiacs and they do not increase sexual desire (‘sex drive’). For these treatments to be effective you need sexual stimulation (foreplay) as well as sexual desire. They will not give you an erection without this (taking a tablet and waiting for something to happen just does not work). If a man has normal erectile function, he does not need to take a PDE5i.

These medicines work by relaxing the blood vessels in the penis, allowing blood to flow into it, causing an erection.

Men who have less firm erections may find their condom slips off. A PDE5i may help prevent this (and make sex safer) by producing a firmer erection.

PDE5i are available in a variety of dose strengths. Many doctors start treatment with a dose in the middle range, which can be reduced or increased as required. The tablets are usually taken ‘on demand’, 30 – 60 minutes before sexual activity, but many men find it better to wait longer to have sex if possible. Don’t forget, you need to be mentally AND physically stimulated to get an erection.

After taking sildenafil, vardenafil or avanafil, they may continue to have an effect for up to 8-10 hours (many men claim to have a good erection the next morning). Tadalafil can have an effect up to 36 hours (earning it the nickname ‘the weekend’ pill). This is useful if things don’t work out for you immediately.

You should not take more than the maximum dose – you simply increase the side effects but not the good effects. You should not take more than one tablet a day. With sildenafil, vardenafil and avanafil, taking the tablets with food may delay and reduce their effects.  This is not a problem with tadalafil.  It is probably safest to avoid alcohol altogether when taking any of these medicines, as this combination may cause dizziness due to a drop in blood pressure.

PDE5i don’t work for everyone. If you haven’t had much success after taking the maximum dose on 8 different occasions, it may be worth asking your doctor if you can try one of the other tablets, as a change can sometimes work, or ask if you can try a daily dose of tadalafil 5mg instead.

It is a good idea to find out how the medicine works on you and what side effects it has, if any, before you drive or have sex with your partner.

What are the most common side effects?

PDE5i also make other blood vessels in the body dilate so you may get facial flushing or a headache. These effects are usually not severe and only temporary. They should not stop you having sex. You may also get a stuffy nose or indigestion, which usually goes with regular use or if the dose is reduced. Visual disturbances may be more likely with sildenafil. Muscle pain and backache may be more common with tadalafil. Backache may also be more likely with avanafil.  Rarely, your erection may last too long (see the section below ‘What if my erection lasts too long?’).

When should you avoid it?

  • If you are taking a medicine containing nitrates, because this combination can cause the blood pressure to drop too low (these include sprays for angina, some tablets for the heart and the recreational drugs known as ‘poppers’ (Amyl nitrite)). If you would like to try a PDE5i and you are taking a nitrate for another reason, talk to your doctor to see if it can be changed
  • If you are taking a different PDE5i, as this combination is not recommended
  • If you are a woman, as PDE5i have not been widely tested in women
  • If you have disease of the heart or blood vessels (cardiovascular disease (CVD)), you should check with your doctor when you get your first prescription that a PDE5i is safe for you to use. As a rough guide, if you do not have any symptoms (e.g. chest pain, irregular heartbeat, dizziness or excessive breathlessness) while walking 1 mile on the flat in 20 minutes, or when briskly climbing 2 flights of stairs in 10 seconds, it is likely to be safe for you to enjoy normal sexual activity

What if it does not work?

If oral treatment does not help you to get an erection, or your erection does not last long enough for you to enjoy your chosen sexual activity, you should tell your doctor. They may suggest help from a sex therapist (see our factsheet ‘Sex therapy’).  If you are an older man, your doctor may want to check your testosterone (see our factsheet ‘Testosterone deficiency’). There are also other effective treatment options available (see our factsheets ‘Injection, urethral and topical treatments for erectile dysfunction’ and ‘Vacuum pump treatment for erectile dysfunction’).

What should you do if your erection lasts too long?

Following the use of a PDE5i, the erection usually goes down with ejaculation. If this does not happen, it may become uncomfortable and you will need to reduce it as soon as possible. Exercise such as running up and down stairs or cycling vigorously will usually work, or try taking a cold shower. An ice bag (such as frozen peas) wrapped around the penis for a short time may also be effective (but don’t overdo this – you want to cool the area not freeze it!). Otherwise, taking an over-the-counter decongestant medicine called Sudafed® (pseudoephedrine HCI) in tablet form may help. But check with the pharmacist that it is ok for you to take this if you have other health problems or are taking other medications. If your erection lasts longer than 4 hours, you should go to a hospital casualty unit or Accident and Emergency Department as soon as you can, because a long delay may damage the penis.

What’s true and what’s not?

  • I take a tablet and get an instant erection – No, they require sexual desire AND sexual stimulation (foreplay) to work
  • ‘I took a tablet and stayed ‘up’ all night’ – The risk of a prolonged erection is very rare. This comment is often made as a result of the jokes that can be related to ED
  • I cannot take a PDE5i if I have a ‘heart problem’ – Not necessarily, particularly if your ‘heart problem’ is stable. Your doctor can check if you are ‘fit for sex’ and if there are any other reasons why you should not take these medications
  • These tablets can cause a heart attack – Heart problems and stroke have been reported with this type of medicine, but it is not clear if they occurred as a result of the patient already having risk factors for them, the drug itself, the sexual activity, or a combination of these or other factors. To reduce the risk of problems, your doctor should check if you are ‘fit for sex’ and if there are any other reasons why you should not take these medicines. It is important to remember that because the tablets dilate your blood vessels to help you get an erection, this may also cause your face to flush and your blood pressure to drop (not rise), and indigestion may feel like heart pain

Who can get it?

At the moment, sildenafil (the generic version of the branded Viagra®) can be prescribed on the NHS to anyone with ED as long as it is safe to do so. Oral treatment with other PDE5i

Is only available on an NHS prescription if you have certain medical conditions (including diabetes, multiple sclerosis, Parkinson’s disease, prostate cancer, spina bifida, polio and certain genetic conditions such as Huntingdon’s disease). PDE5i may also be prescribed on the NHS if you are receiving or have received certain treatments (including pelvic or prostate surgery, dialysis for kidney failure and kidney transplant), or if you are suffering severe distress as a result of your ED.  If you are not entitled to these treatments on the NHS, you may be able to pay for them privately. Ask your doctor or pharmacist for more information.

What is the Take Home Message?

Oral treatments for ED can be very successful, but they require sexual desire AND sexual stimulation to work

Where can you get more information?

The Sexual Advice Association is here to help. We cannot give individual medical advice, but we can answer your questions on any sexual problems and put you in touch with local specialist practitioners. We also have a number of factsheets and booklets on sexual problems and related issues for men and women that can be downloaded from our website or requested. Please feel free to email us or phone our Helpline (our contact details are at the bottom of this page).

You can also visit the NHS Choices website at www.nhs.uk for information and advice on many different health and lifestyle topics.

Further reading

Download or request our factsheets ‘Erectile dysfunction and the heart’ and/or ‘Explaining sexual problems to your GP


By donating to the Sexual Advice Association, you will know that you are helping improve the lives of people living with sexual problems. If you are interested in donating, please click here or contact us for more information (details at the bottom of this page).

Thinking About Sex Day: February 14th

Launched by the Sexual Advice Association, Thinking About Sex Day (TASD) is designed to encourage everyone to think about the physical and psychological issues surrounding sexual activity.

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