Formerly SXC Health Solutions (and last year's top dog on the Fastest-Growing list), this pharmacy benefits manager (PBM) completed its merger with rival Catalyst Health Solutions in July with a cash and stock deal worth over $4 billion. The combined company is now the fourth largest PBM in the US, serving about 25 million members. The additional revenues that will result from the Catalyst deal have not yet been reflected in the newly-created Catamaran's numbers but the company expects to generate combined annual revenues of around $13 billion. For the first six months of this year, SXC Health revenues came in at $3.3 billion - up 48% year-on-year. PBMs help their clients -- such as unions, third-party health care plan administrators, state and federal government entities -- to manage the cost of their prescription drug programs by leveraging their buying power to secure price discounts. -- N.S.