Eli Lilly (NYSE:LLY) is one of today's biggest players in the erectile dysfunction space. Its drug Cialis garnered more than $1.9 billion in 2012, but how important is this single therapeutic to Lilly's total business? What are the competitive dynamics of the erectile dysfunction market, and how do Pfizer's (NYSE:PFE) Viagra and VIVUS' (NASDAQ:VVUS) drug Stendra compare to Cialis? In this video, health care analyst Max Macaluso examines these issues for investors.