Daiichi Sankyo Co. forecast a record loss for a Japanese drugmaker, reversing its earlier estimate of profit this year, citing writedowns on its takeover of India's Ranbaxy Laboratories Ltd.

The net loss will be ¥316 billion for the year ending March 31, compared with previously predicted net income of ¥65 billion, Tokyo-based Daiichi Sankyo said in a statement Friday to the Tokyo Stock Exchange.

Shares of Japan's third-biggest drugmaker underperformed its biggest competitors since Chief Executive Officer Takashi Shoda bid for Ranbaxy last June to enter the market for lower-priced generic medicines. He paid ¥488.7 billion and has written down almost three-fourths of that since the acquisition was completed.