A handful of trade groups are angered over the prospect of Express Scripts Inc. and Medco Health Solutions Inc. uniting. The National Association of Chain Drug Stores (NACDS), the National Community Pharmacists Association (NCPA) and nine independent pharmacies filed a lawsuit on March 29 in the U.S. District Court for the Western District of Pennsylvania, alleging the merger is a threat to the viability of local pharmacies.

St. Louis-based Express Scripts entered a deal to purchased Medco in July 2011 for $29.1 billion, which would create what was billed as the nation's leading health care services company. That deal was made official today. Combined, the companies say the merger allows them the ability to lower health care costs, create better models of care and improve patients' adherence to prescribed treatment regimens.

“Our merger is exactly what the country needs now,” George Paz, Express Scripts chairman and CEO, said in a statement. “It represents the next chapter of our mission to lower costs, drive out waste in healthcare and improve patient health. We remain focused on formulary management, channel management and closing gaps in care, which will allow us to further improve the health of people with chronic and complex medical conditions.”