Sildenafil is a treatment for adult men with erectile dysfunction, sometimes known as impotence.

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What is Sildenafil?

Sildenafil is the name of the active medical ingredient in Viagra.  It also comes in the same strengths and dosages as Viagra, therefore Sildenafil and Viagra will have identical effects. Sildenafil is used to treat erectile dysfunction (ED) and has proven to be extremely effective in ameliorating the effects ED enabling men to achieve stronger erections and last longer during penetrative sex.

Most erectile dysfunction treatments including Sildenafil (Viagra) belong to a class of medications known as PDE-5 (Phosphodiesterase 5) inhibitors. PDE-5 inhibitors will only work if the individual who has taken the medication is sexually aroused.

Alternatives to Sildenafil in this medication class are Cialis, Spedra and Levitra.

What are the benefits of Sildenafil?

Sildenafil is a treatment for adult men with erectile dysfunction, sometimes known as impotence.

  • Sildenafil CAN also help improve sexual confidence
  • Sildenafil CAN be used in men with cardiovascular (heart) disease
  • Has a long-established use for erectile dysfunction

How does Sildenafil work?

Sildenafil enhances the flow of blood into the blood vessels of the penis facilitating an erection.

An erection is initiated when sexual arousal stimulates centres within the brain thereby increasing levels of a chemical called nitric oxide.

This in turn activates the production of cyclic guanosine monophosphate (cGMP) throughout the body. Within the penis, cGMP relaxes the penile vessel walls allowing the arteries to fill with blood, this then produces an erection.

In cases of erectile dysfunction, men have a defective cGMP pathway and an enzyme called PDE-5 responsible for the degradation of cGMP is hyperactive. This prevents cGMP from functioning as it should thereby reducing blood flow to the penis.

Sildenafil citrate is a PDE-5 enzyme inhibitor i.e. it blocks activity, this allows the cGMP to last longer within the bloodstream and function correctly. Adequate concentrations of cGMP within the body allows the penile vessels to dilate and take in more blood, thereby facilitating a stronger erection.

What if Sildenafil doesn’t work?

  • Ensure that you are taking the correct strength. The dosage you are taking may not be enough. If you are on the lower dosages of 25mg or 50mg please discuss with your doctor to change your dosage if appropriate.
  • Sildenafil is not a continual medication, for it to work you must be sexually aroused.
  • Certain other medications, some foods and drinks may reduce the effect of Sildenafil. Heavy ‘fatty’ meals taken with your tablet or consumption of alcohol will have some impact on the effectiveness of your tablet.

Can women have Sildenafil?

It currently is licensed for ONLY men. We will only consider providing Sildenafil to men over 18 years of age.

How to take Sildenafil?

How to make Sildenafil the most effective 1. Avoid taking Sildenafil with a large ‘fatty’ meal as this can slow down the absorption of Sildenafil, therefore, taking longer to work.

  1. It is best to take Sildenafil on an empty stomach.
  1. Limit alcohol consumption, this can affect the absorption of Sildenafil and also alter your blood pressure as well as increase side effects such as dizziness.
  1. Avoid ingesting milk, watermelon and grapefruit juice at the same time as your tablet.
  1. Swallow the tablet whole, crushing the tablet can degrade and reduce the effectiveness of the active ingredient.

If you are not benefiting from Sildenafil despite having already increased your dosage and have followed all of the advice listed above, it is recommended you consult your doctor.

How long does it last?

Sildenafil lasts up to 4 hours in the bloodstream ( optimal plasma concentration) and its effects wear off after that period. It starts working after 30-60minutes in most men and is most effective within the first 2 hours.

Dosages Sildenafil can be prescribed in varying strengths of 25mg, 50mg and 100mg. All of these are available from the Access Doctor website.

Low strength Sildenafil 25mg tablets are recommended for men over 65 years of age and those that are sensitive to the effects of sildenafil.

Standard strength Sildenafil 50mg tablets are the usual starting recommended dose by the doctor.

Higher-strength Sildenafil 100mg tablets are the maximum recommended dosage. It is usually only recommended by the doctor after men have not achieved adequate benefits with the standard strength capsules.

Precautions & Side-effects

Sildenafil tablets are only licensed and suitable for males over the age of 18 who suffer from erectile dysfunction.

Sildenafil is not suitable for women and those under the age of 18years.

Sildenafil may be unsuitable for those who identify with any of the following, it is recommended they consult a doctor who can assess suitability in such cases:

  • Have liver or kidney disease
  • Have cardiovascular disease e.g. heart problems (heart disease, myocardial infarction) or stroke
  • Have chest pain symptoms
  • Suffered a stroke within the past 6 months
  • Have low blood pressure
  • Have sickle cell anaemia
  • Have intolerance to galactose
  • Have deformity to the penis eg Peyronie’s disease or damage to the penis
  • Are you already on nitrate medication e.g. GTN spray It is vital you state all the information as to the best of your knowledge regarding your past medical history and current medical conditions when completing our consultation, this helps our doctors make safe decisions and provide you with the best treatment options
  • Please read the patient information leaflet for other risk factors.


Sildenafil is known to interact with certain other medications. It is vital to be cautious when taking Sildenafil concurrently with some medications, foods and beverages:

Grapefruit and grapefruit juice, can increase the level of sildenafil within the body and cause significant reductions in blood pressure.

Alcohol consumption can exacerbate some side effects such as dizziness and flushing.

Blood pressure medication can compound the blood pressure reducing effects.

Nitrates can lower blood pressure and cause flushing.

Can Sildenafil lower blood pressure?

Sildenafil was initially invented and went to clinical trials for the purposes of high blood pressure, studies have shown that taking these tablets reduces systolic blood pressure by between 8 to 10 mg Hg, however, it has never been approved or licensed for use in systemic hypertension. It is used to treat Pulmonary artery Hypertension (pulmonary hypertension).

Caution should be used in using Sildenafil with anti-hypertensives, they should be avoided with a specific class of anti-hypertensives called alpha-blockers and medications containing nitrates or their derivatives, in such cases your blood pressure may become dangerously low.

This product is safe to use with many heart medications. Always inform your doctor of any other medications you are taking, before starting Sildenafil.

During your consultation, please list all your blood pressure medications such as Ramipril, Amlodipine and Bendroflumethiazide.

Side effects

Side effects can occur with all medications. If you are sensitive to PDE-5 inhibitors you may experience the following side effects:

feeling sick.
hot flushes, including facial flushing.
a colour tinge to your vision or blurred vision.
stuffy nose.

As your body gets used to the medication and the dose, these usually subside. If you get persistent side effects stop taking the medication and seek advice from your doctor.

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