Pharmaceutical giant Merck has reported a $500m (£310m) loss in the final three months of last year, largely thanks to $4bn of restructuring costs related to its acquisition of Schering-Plough.
The loss compared with a profit of $6.5bn in the same quarter a year ago.
Merck agreed to pay $41bn for its rival Schering-Plough in 2009, creating one of the world's biggest drug companies.
Merck also forecast earnings for the year ahead below Wall Street estimates, sending its shares down 2.7%.
The company said it expected earnings per share of $3.64 to $3.76 in 2011. Analysts had been expecting $3.82.
It also took a $1.7bn charge related to a major setback in clinical trials for its experimental anti-clotting drug, vorapaxar.