What Is Viagra?

Viagra is an oral drug developed by Pfizer to treat one of the most widespread sexual disorders - erectile dysfunction.
The active ingredient in this drug, which got the approval from the US Food and Drug Administration (FDA) in 1998, is sildenafil citrate.
It works by dilating blood vessels and blocking the phosphodiesterase type 5 enzyme. This helps to improve blood flow to the penis and, thus, achieve and maintain an erection.
Viagra is great for men who are diagnosed with erectile dysfunction, simply experience inconsistent ability to achieve an erection or cannot sustain a prolonged erection.
The dosage of Viagra depends on the nature of the sexual disorder, health conditions, age and other factors. The dosage can only be prescribed by a physician upon a careful medical examination. Usually, men are prescribed 50 mg of Viagra daily. The drug is also available in 25 mg and 100 mg pills. 
Viagra should be taken 30-60 minutes prior to the sexual ativity for it to take effect. The Viagra effect usually lasts up to 4 hours or less if taken with fat foods or alcohol.
Pfizer proved that Viagra can be used to treat conditions other than erectile dysfunction. As such, research showed that the drug is ideal for treatment of high-altitude pulmonary edema, pulmonary arterial hypertension and sexual function in women taking antidepressant drugs.