Researchers at Pfizer discovered the effects of Viagra by accident. Originally, the drug was meant to treat angina, but it had an unintended side effect – harder erections that lasted longer. After further investigation, the researchers at Pfizer discovered that Viagra works because it increases blood flow to the penis.
Viagra was the first FDA-approved medication used to treat erectile dysfunction in men. Approved in 1998, it quickly became a blockbuster drug, with almost $3 billion per year in sales. Clinical trials have shown that Viagra helps 70-80% of men get and maintain an erection sufficient for sexual intercourse.
Before Viagra, treatments for erectile dysfunction included penile implants, genital suppositories, and direct injections. These treatments were painful, expensive, and interfered with spontaneity. Viagra usually starts working in as few as 30 minutes. It typically has mild side effects, including headache, digestive upset, and blurred vision.