Viagra is the most well-known of the three as it has been around for over 15 years. It works within an hour of taking a tablet, and is best taken on an empty stomach. The effects of Viagra will last for four to six hours.
Viagra was developed and originally marketed by the pharmaceutical company Pfizer, and until 2013 Pfizer was the only company allowed to sell it. When Pfizer’s patent on Viagra expired, the market was open for other companies to produce the medicine, albeit under its generic name Sildenafil, rather than the brand name Viagra.
Sildenafil contains exactly the same active ingredient as Viagra (sildenafil citrate), and works in the same way. However, because it is the generic version of the medicine, rather than the brand, Sildenafil is considerably cheaper.
But if you have cardiovascular system disease, Don't use it!
The most important thing should be paid attention to!