Sildenafil, also translated as sildenafil, is a drug for the treatment of male erectile dysfunction that was accidentally invented during the development of drugs to treat cardiovascular diseases. It is generally known by its commercial name Viagra (registered in mainland China) It is widely known as Viagra (registered as Viagra in Taiwan and Hong Kong). However, compared to the commercial name sildenafil, its common name "Viagra" in China is more widely used and has a greater impact. Because Pfizer holds a patent on sildenafil, the company's Viagra, which is made from the citrate (citrate) of sildenafil, is currently the only drug on the market that legally contains sildenafil as its main ingredient.