SandRidge Energy Inc. adopted a "poison pill" plan Monday in its effort to buy Bonanza Creek Energy Inc. of Denver for $746 million.

SandRidge's board said its plan is "designed to deter the acquisition of actual, de facto or negative control of the company by any person or group."

The board didn't specifically mention activist investor Carl Icahn, who owns about 13.5 percent of the Oklahoma company (NYSE: SD), but the "poison pill" plan would prevent Icahn from buying more SandRidge shares.

Icahn opposes Sandridge's plan to buy Bonanza Creek (NYSE: BCEI) and calls the acquisition "nonsensical," according to the Wall Street Journal. Other large SandRidge shareholders also opposed the Bonanza Creek purchase, according to the Journal.

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