Author: Pfizer Limited


Long information

What is it?

Viagra is a medicine that contains the active substance sildenafil. It is available as blue, diamond-shaped tablets (25, 50 or 100 mg).

Table of Contents
What is it used for?
How is it used?
How does it work?
How has it been studied?
What benefits has it shown during the studies?
What is the risk associated?
Why has it been approved?

What is it used for?

Viagra is used to treat adult men with erectile dysfunction (sometimes called impotence), when they cannot get or keep a hard penis (erection) sufficient for satisfactory sexual activity. For Viagra to be effective, sexual stimulation is required.
The medicine can only be obtained with a prescription.

How is it used?

The recommended dose of Viagra is 50 mg taken as needed about one hour before sexual activity. If Viagra is taken with food, the onset of activity may be delayed compared with taking Viagra without food. The dose may be increased to a maximum of 100 mg or decreased to 25 mg depending on the effectiveness and side effects. Patients with liver problems or severe kidney problems should start treatment with the 25-mg dose. The maximum recommended dosing frequency is one tablet per day.

How does it work?

The active ingredient in Viagra, sildenafil, belongs to a group of medicines called phosphodiesterase type 5 (PDE5) inhibitors. It works by blocking the phosphodiesterase enzyme, which normally breaks down a substance known as cyclic guanosine monophosphate (cGMP). During normal sexual stimulation, cGMP is produced in the penis, where it causes the muscle in the spongy tissue of the penis (the corpora cavernosa) to relax, allowing the flow of blood into the corpora, producing the erection. By blocking the breakdown of cGMP, Viagra restores erectile function. Sexual stimulation is still needed to produce an erection.

How has it been studied?

Viagra has been studied in four main studies including 1,690 men aged 19 to 87 years, where it was compared with placebo (a dummy treatment) for between 12 and 26 weeks. Two of these studies used fixed doses (patients allocated to 25, 50 or 100 mg) and two studies were flexible (patients started on 25 mg and could be moved to 50 or 100 mg depending on their response). In addition, there were studies in patients with spinal cord injury and with diabetes. The main measure of effectiveness was based on the ability of the men to get and maintain an erection. This was recorded in a special questionnaire completed at home using a scoring system on a five-point scale, where a score of 5 represents the best result.

What benefits has it shown during the studies?

Viagra was significantly more effective than placebo in all studies. In the questionnaire, scores for the question on how often the patient was able to achieve intercourse went from about 2 without treatment to 3 or 4 with Viagra 50 mg. In the fixed-dose studies, the proportions of patients reporting that treatment improved their erections were 62% (25 mg), 74% (50 mg) and 82% (100 mg), compared with 25% on placebo.

What is the risk associated?

The most common side effect with Viagra (seen in more than 1 patient in 10) is headache. For the full list of all side effects reported with Viagra, see the Package Leaflet.
Viagra should not be used in people who may be hypersensitive (allergic) to sildenafil or any of the other ingredients, or where sexual activity is inadvisable (e.g. men with severe heart disease such as unstable angina or severe heart failure). It should also not be taken by patients who have ever had loss of vision because of a problem with blood flow to the nerve in the eye (non-arteritic anterior ischemic optic neuropathy or NAION). Viagra should not be taken with nitrates (medicines used to treat angina). Because Viagra has not been studied in patients with severe liver disease, hypotension (low blood pressure), recent stroke or myocardial infarction (heart attack), or a hereditary eye disease, such as retinitis pigmentosa, these patients should not use it.

Why has it been approved?

The Committee for Medicinal Products for Human Use (CHMP) decided that Viagra?s benefits are greater than its risks for the treatment of men with erectile dysfunction. The Committee recommended that Viagra be given marketing authorisation.

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