Sildenafil for erectile dysfunction (Nipatra, Viagra, Vizarsin)

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Sildenafil is for the treatment of adult men with erectile dysfunction.

Take a tablet about an hour before you plan to have sex. Do NOT take more than one dose in 24 hours.

When you collect your prescriptions, check the brand and strength of the tablets. If the appearance is not the same as usual, speak with your doctor or pharmacist for further advice.

Type of medicinePhosphodiesterase type-5 inhibitor
Used forErectile dysfunction in adult men
Also calledNipatra®; Viagra®; Vizarsin®
Available asTablets and chewable tablets

Erectile dysfunction (sometimes called impotence) means that you cannot get or maintain a proper erection. There are several causes, the most common being due to a narrowing of the arteries that take blood to the penis.

Sildenafil works by preventing the action of a chemical in your body, called phosphodiesterase type-5. This helps to widen (relax) blood vessels and improves the flow of blood to the penis following sexual stimulation. This helps to maintain an erection.

Sildenafil is available on prescription. Non-branded (generic) tablets of sildenafil are available on the NHS, but the brand Viagra® can only be prescribed on the NHS for men with erectile dysfunction resulting from certain medical conditions.

Another brand of sildenafil tablets called Revatio® is used in a completely different condition called pulmonary arterial hypertension - please see the separate medicine leaflet called Sildenafil for pulmonary hypertension if you have been prescribed this brand of sildenafil tablets.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking sildenafil it is important that your doctor knows:

  • If you have any disease, injury or deformity of your penis.
  • If you have a heart condition, or blood vessel disease.
  • If you have had an eye condition causing loss of vision.
  • If you have low blood pressure or angina.
  • If you have any problems with the way your liver works or with the way your kidneys work.
  • If you have had a stroke or a heart attack.
  • If you have a condition which causes bleeding, such as a stomach ulcer.
  • If you have sickle cell disease.
  • If you have ever had bone marrow cancer or leukaemia.
  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines, and recreational drugs.
  • If you have ever had an allergic reaction to a medicine.
  • Before you take sildenafil, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about the tablets and will provide you with a full list of the side-effects which you may experience from taking them.
  • Take sildenafil exactly as your doctor tells you to. It is intended to be taken before sexual activity - it is NOT for continuous daily use. You should take one tablet about an hour before you plan to have sex, although it may still be effective up to five hours after taking the tablet. You can take the tablet either before or after food but, if you have just eaten a large meal, it may take longer for it to work.
  • There are three strengths of sildenafil tablets: 25 mg, 50 mg and 100 mg. It is likely that you will be given the 50 mg strength tablet to begin with, but this may be changed subsequently depending upon how you react. Each time you collect a prescription, check to make sure it contains the strength of tablet you are expecting.
  • If you have been supplied with a brand of tablet called Nipatra®, these are chewable tablets. Chew the tablet before you swallow it.
  • Do not take more than one dose of sildenafil in any 24-hour period.
  • You and your partner will still need to engage in foreplay, just as you would if you were not taking a medicine for erectile dysfunction. Sildenafil will not cause an erection unless you are sexually aroused.
  • Do not drink large amounts of alcohol before you plan to take sildenafil. Drinking too much alcohol can reduce your ability to get an erection and this may prevent you from getting the maximum benefit from the tablets.
  • It is recommended that you do not drink grapefruit juice with sildenafil. This is because there is a chemical in grapefruit juice which can increase the amount of sildenafil in your bloodstream and this makes side-effects more likely.
  • Keep your regular appointments with your doctor so your progress can be monitored. If you feel the tablets are too strong for you, discuss this with your doctor as your dose may need to be reduced. Alternatively, if you do not get an erection after taking sildenafil, or if it does not last long enough for you to have sex, you should discuss this with your doctor - do not take more tablets than you have been told to.
  • You should not take sildenafil if you are using any other products or taking any other medicines to treat erectile dysfunction.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with sildenafil. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Very common sildenafil side-effects (these affect more than 1 in 10 men)
What can I do if I experience this?
HeadacheAsk your pharmacist to recommend a suitable painkiller
Common sildenafil side-effects (these affect less than 1 in 10 men)What can I do if I experience this?
Flushing, feeling sick, indigestion, blocked noseThese should soon pass
Feeling dizzy, visual changes such as blurred vision or colour distortionIf either of these happen, do not drive or use tools or machines until your reactions/vision have returned to normal

Important: if your erection lasts for longer than four hours, or if you get chest pains or a sudden loss of vision, contact a doctor for medical attention straightaway.

If you experience any other symptoms which you think may be due to the tablets, speak with your doctor or pharmacist for further advice.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

If you buy any medicines, check with a pharmacist that they are safe to take with your other medicines.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
1490 (v25)
Last Checked:
04/02/2015
Next Review:
03/02/2018
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