The World’s best selling Erectile Dysfunction drug Viagra, may have to face STIFF competition soon as Vivus Inc wins approval for Avanafil, which is a faster acting rival to Viagra. Avanafil, which will be sold under the brand name Stendra, is the first new drug in the category in a decade. The FDA has approved Vivus’ Erectile Dysfunction drug Stendra, and the company hopes its rapid mode of action will help take market space away from its key competitors Viagra, Cialis and Levitra. Stendra belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors, which are used to help increase blood flow to the penis. Researchers found it to be more selective than the older drugs, meaning it could have fewer unintended effects. "Higher selectivity should translate into fewer side effects," said Dr Wayne Hellstrom. "It's going to add more excitement" to the field. The drug carries the same warnings as Viagra, Cialis and Levitra, including that it should not be used by men who also take nitrates due to the potential for a sudden dangerous drop in blood pressure and the now famous warning to see a doctor if an erection lasts more than four hours. Viagra (Sildenafil) was the first drug to treat Erectile Dysfunction but Vivus believes that Stendra has an advantage over Viagra, as it can provide an erection in around 15 minutes. This is half the time Viagra takes to kick start. “Stendra is the first of a new generation of PDE5 inhibitors, and the approval marks an exciting new milestone for the millions of men suffering from erectile dysfunction who are in need of a new treatment option,” said Dr Wayne Hellstrom, Professor of Urology and chief of Andrology at Tulane University School of Medicine in New Orleans. "This approval expands the available treatment options to men experiencing erectile dysfunction, and enables patients, in consultation with their doctor, to choose the most appropriate treatment for their needs," Victoria Kusiak, deputy director of the Office of Drug Evaluation in the FDA's Centre for Drug Evaluation and Research, said in a statement. ED affects as many as 30 million men in the U.S. according to Vivus, who said the market opportunity for these medical treatments continues to grow with worldwide sales of PDE5 inhibitors exceeding $5 billion in 2011. According to a forecast, Stendra sales have the potential to reach up to $300 million a year. Viagra had sales of about $2 billion in 2011. Pfizer’s Viagra has patent protection in the US until 2019, and made the firm over $2 billion in sales last year - patents for Cialis and Levitra will expire sooner in 2016 and 2018. Stendra is currently awaiting a European approval decision.