Viagra (sildenafil) facts

Viagra does not cause a man to be sexually aroused. Viagra is only effective if you are sexually aroused. To understand how it works you need to understand the mechanics of how a man gets an erection. When you get sexually stimulated, the nervous system in the erectile tissue of your penis releases nitric oxide (NO).

The nitric oxide stimulates an enzyme that produces something called a messenger cyclic guanosine monophosphate (cGMP). The cGMP relaxes the smooth muscle cells. One result of this is that the arteries in your penis dilate and the blood can flow into your penis more easily. Another result is that the erectile tissue itself fills with blood. Both of these process result in an erection. Viagra works by maintaining the level of cGMP in the smooth muscle cells.

If you are not turned on, your brain will not stimulate the release of any nitric oxide and you will not produce any cGMP.

Clinical studies have shown that when compared to placebo, Viagra and the other drugs in the same class, result in significant improvement in erectile function. Although established to be a safe and effective drug, Viagra isn't appropriate for everyone and may not work in all cases.

Viagra can slightly lower blood pressure. This is not a problem for most men. But Viagra's effect on blood pressure is exaggerated if the Viagra is taken with a nitrate drug.

Nitrates are one of the treatments doctors prescribe for angina. If you take Viagra when you are also taking nitrates, the combined effect of the Viagra and the nitrates can lower your blood pressure to such an extent that it could prove fatal. Never take Viagra at the same time as taking nitrates.

If you have a heart condition it is important that you discuss this with the doctor before taking Viagra. Viagra may not be appropriate because of the danger of interacting with the nitrates.

Viagra is not currently licensed for use by women.

On average, Viagra becomes effective in just under an hour when you take a tablet on an empty stomach. Viagra can remain effective for between four and six hours. If you take it after a meal that has a high fat content, it may take longer than an hour to become effective.

Viagra is available in three dosages: 25mg, 50mg and 100mg. Some men may respond to a lower dose of Viagra. Some men may already be taking medicines that interact with Viagra and thus need to adjust the Viagra dosage they are taking.

The doctor needs to decide which dosage of Viagra is most appropriate. The doctor will take into account potential drug interactions, your age, the severity of your erectile dysfunction and any previous experience you have had with Viagra.

Viagra might not work the first time you take it. Most doctors advise taking Viagra at least eight times before trying a different medicine.

Viagra's Side effects are generally mild and brief. Viagra's most common side-effects are headache and facial flushing. Less frequently, men taking Viagra have reported indigestion, a stuffy nose and a blue tint to the vision.

Viagra interacts with many drugs. The following list is not complete but it is important to inform the doctor of all prescription and non-prescription medication taken, especially:

• nitrate medications (e.g. glyceryl trinitrate (GTN), nitroglycerin, isosorbide mononitrate or dinitrate)
• nitroprusside
• cimetidine
• erythromycin
• azole antifungals (e.g., itraconazole, ketoconazole)
• mibefradil
• rifamycins (e.g., rifampicin)
• Alpha blockers, prescribed for prostate disease or high blood pressure
• Ritonavir, Amyl, Butyl or Isopropyl nitrates ('Poppers')

Men who have any of the following conditions should also avoid taking it:

• severe heart or liver problems
• recent stroke or heart attack
• low blood pressure
• certain rare inherited eye diseases

Viagra will resolve the underlying cause of erectile dysfunction although if the cause is primarily psychological, it may help to break the cycle of anxiety and failure associated with being unable to achieve a satisfactory erection.

A blood test for diabetes should be performed along with cholesterol and triglyceride blood tests. It is becoming increasingly accepted among doctors that sex hormone levels (Testosterone) should also be checked by way of a blood test.

The other drugs, Levitra and Cialis work in similar ways. Viagra is generally prescribed as the first line treatment. Cialis has a much longer half-life than Viagra and Levitra and therefore its effect lasts much longer.

This does not mean one has prolonged erections but the length of time available for further erections is increased without the need to take further doses. It also means however that the side effects if present will last longer. Levitra, like Cialis, can be taken with food whereas Viagra should be taken on an empty stomach.

Some studies have shown Levitra to be more suitable for men suffering from diabetes. Other treatments include Caverject ('Alprostadil'), which is a medication injected directly into the penis and MUSE (another form of 'Alprostadil'), which is a pellet inserted into the urethra. These may be of use for men who have to take Nitrates and are therefore unable to take the PDE5 inhibitors.

The use of vacuum pumps and other mechanical devices for producing and maintaining erections are alternatives to taking medication.