Eli Lilly (LLY 5.04%) currently has several blockbuster drugs on the market -- but lookout investors, there are patent expirations aplenty for this pharma giant ahead. Much like Merck (MRK 6.80%), which is dealing with the recent loss of exclusivity for its top-selling drug Singulair, Lilly has to rely on its pipeline to quickly produce drugs with massive market opportunities. In this video, health-care analyst Max Macaluso dives into the company's most worrying patent expiration of 2013.