Mallinckrodt plc plans to amp up its hospital-based drug portfolio with the acquisition of privately held Ikaria Inc. in a transaction valued at approximately $2.3 billion. Hampton, N.J.-based Ikaria, which is focused on therapies and delivery systems for critically ill infants in hospital neonatal intensive care unit (NICU) settings, markets Inomax, a continuous flow version of inhaled nitric oxide.