New York  - Drug maker Merck & Co will merge with rival Schering-Plough Corp in a deal valued at 41.1 billion dollars, the companies announced Monday.

The deal would double the number of medicines under the final stages of development by Merck to 18 and create the second-largest US pharmaceutical firm.

Under the agreement, Schering-Plough shareholders will receive 0.6 shares of Merck and 10.50 dollars for each share, amounting to a total of 23.61 dollars per share.

The deal is to be completed in the fourth quarter and was approved unanimously by the boards of both companies. (dpa)