Merck and Schering-Plough: Top 10 deals of 2009

Who: Merck
With: Schering-Plough
What:  $41.1B buyout

Summary: The M&A fever continued in March with Merck's acquisition of long-time partner Schering-Plough. The two had been working on cholesterol drugs Vytorin and Zetia, which have caused controversy over questions of their effectiveness. As with the Pfizer and Roche deals, the merger has involved layoffs. Merck CEO Richard Clark said that 15 percent of the companies combined workforces would be cut. With a total workforce of 106,000, that adds up to about 16,000 workers.