Pharmaceutical giant Merck posted a loss of $500 million (£310 million) in the December quarter, due to a restructuring cost of $4 billion related to its acquisition of rival drug maker Schering-Plough.
The Pharma giant had posted a net profit of $6.5 billion over the same period last year.
Merck had acquired Schering Plough in 2009 for a total consideration of $41 billion, creating one of the biggest pharmaceutical companies of the world.
The company also issued its earning forecast for 2011, which fell short of analysts expectations. It projected an EPS (Earning Per Share) between $3.64 and $3.82.
Merck had suffered a major blow when its experimental anti-clotting drug Vorapaxar failed in clinical trials and the company had to write off $1.7 billion in development costs.