Following the announcement of Valeant Pharmaceuticals International Inc.'s plans to acquire Raleigh, North Carolina-based Salix Pharmaceuticals Ltd. for $10.1 billion late last month, a rival $11.2 billion bid for the target emerged Wednesday from Endo International plc.

Skadden, Arps, Slate, Meagher & Flom, a firm familiar with twisted pharmaceutical takeover battles, is serving as lead counsel to Endo on its offer for Salix. The firm is also handling finance and antitrust aspects of Valeant's bid for the company. Skadden declined to comment on its work representing both potential Salix acquirers.

The deal between Canada's Valeant and Salix, a maker of medicines for the treatment of gastrointestinal illnesses, topped Deal Watch in late February and saw Sullivan & Cromwell private equity practice leader Alison Ressler snag Dealmaker of the Week honors for her work advising the would-be acquirer. Salix turned to Cadwalader, Wickersham & Taft for outside counsel—the firm grabbed a role for the company last summer on a since-scuttled corporate inversion—as Debevoise & Plimpton and Willkie Farr & Gallagher line up for its financial advisers.