Responding to Allergan's ($AGN) adamant rejection of its $46 billion buyout offer, Valeant ($VRX) has quickly fired back, saying that it plans to bump its bid on May 28th. In a release this morning Valeant CEO J. Michael Pearson told Allergan's shareholders that he'll also be spelling out reasons why they should ignore Allergan's position and embrace the hostile takeover. Pearson and hedge fund operator Bill Ackman have been circling Allergan, laying out plans to chop into its budget right after they take control. Allergan has been spending more and more money on R&D in recent years, a field that Valeant has avoided as much as possible. Release