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Sildenafil is an erectile dysfunction (ED) medication. It's the generic version of the medicine Viagra, meaning it contains the same active ingredient. This medication is part of the PDE-5 inhibitor group which works by increasing the blood flow to the erectile tissue in the penis, helping men with ED get a firmer and longer lasting erection, when sexually aroused.

Key Features
  • Works in the same way as Viagra and has the same active ingredient
  • Typically much cheaper than Viagra
  • Taken one hour before sex and can remain effective for up to four hours

About Sildenafil

How does Sildenafil work?

Sildenafil works by inhibiting the enzyme PDE5. This increases the body’s level of cGMP (cyclic guanosine monophosphate), a chemical which relaxes the smooth muscle cells in the blood vessels within the penis. This means that more blood can flow into the penis during periods of sexual arousal, helping you to achieve and maintain a firmer and longer-lasting erection. It is important to remember that Sildenafil will only help you attain an erection if you are sexually aroused.

When should I take Sildenafil?

Sildenafil should ideally be taken approximately one hour before sexual activity commences. However, the effects of Sildenafil can last for up to four hours, meaning that it can be taken between 30 minutes and four hours before sex begins. If taken with a heavy meal, Sildenafil will take longer to work and may not be as effective.

Sildenafil FAQs

How do I take Sildenafil?

Sildenafil should be taken around 60 minutes before sex. Sildenafil is most effective when taken on an empty stomach, and with no more than one or two units of alcohol. Do not take more than one tablet within a 24 hour period or combine sildenafil with other ED medicines.

How quickly does Sildenafil work?

Sildenafil starts to work within 60 minutes and can remain effective for around four hours. However this does not mean that your erection will last that long, simply that you will be able to get an improved erection within that period of time.

How effective is Sildenafil at treating erectile dysfunction?

Sildenafil has been shown to be very effective in helping many men with ED to get an improved erection when sexually aroused.

Sildenafil does not treat the underlying cause of the ED. It can however help improve your confidence and reduce the anxiety and stress resulting from having the ED itself.

ED is often a symptom of a more serious underlying physical health problem - such as diabetes, high blood pressure, a high cholesterol or a hormonal condition. Most commonly it is due to underlying vascular disease (narrowing of the blood vessels). This can be an early warning sign of heart disease and stroke, particularly if you are over the age of 40. So it is really important that you have the tests we recommend with your doctor to identify and treat any underlying health issues and risk factors.

ED can also be caused by psychological problems such as stress, anxiety and depression.

What are the side effects associated with Sildenafil?

The side effects associated with Sildenafil are generally mild to moderate and of a short duration, the most common of which include:

• Facial flushing
• Headaches
• Light-headedness
• Blue tint to vision
• Indigestion
• Stuffy nose

If you experience any chest pain when using sildenafil or your erection lasts for longer than four hours then please contact the emergency services and seek medical help immediately.

Please read the patient information leaflet which comes with the medication, before taking Sildenafil, for a full list of potential side effects and warnings.

Does Sildenafil interact with other medicines?

Sildenafil should not be taken if you are taking certain other medications due to serious and potentially life threatening interactions. It is really important that you give us a full list of ALL the medicines you are taking everytime you use our service.

Do not use Sildenafil if you are taking Nicorandil or any Nitrates. 

Nitrates are found in some heart medications such as a GTN spray or tablets that you put under your tongue and isosorbide mononitrate/dinitrate used for angina, as well as in certain recreational drugs such as “poppers”, “room odorizers” and “aromas”. They can also be found in other medications so it's very important that you list all the medicines and recreational drugs you have or are taking when asked. This is because when combined with ED medications, they can cause a serious and life threatening drop in blood pressure, which can be fatal.

If you are taking alpha-blockers (such as alfuzosin, doxazosin, tamsulosin or terazosin) you should make sure there’s at least a six hour gap between taking the alpha-blocker and taking Sildenafil as the combination can cause a dangerous drop in your blood pressure. 

This is not a full list of all the medication interactions - Sildenafil can interact dangerously with other medicines. Please list ALL the medicines you are taking when asked. If you subsequently start taking a new medication, before taking your Sildenafil please always check with our doctors first by sending a message via your Patient Record, to ensure the Sildenafil is still safe to take.

What happens if I am not suitable for a prescription? 

If our doctors think that an online consultation is not appropriate we will let you know via your Patient Record and refund you straight away. Please note that refunds take up to five working days to appear on your statement.

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