Inline liquid drug medical device having a longitudinal device axis, a housing with a linear displaceable sliding flow control member displaceable along a transverse bore from a first flow control position for establishing flow communication between a first pair of ports for liquid drug reconstitution purposes to a second flow control position for establishing flow communication between a second pair of ports for liquid drug administration purposes, and a manually operated actuating mechanism for applying a linear displacement force for urging the flow control member to slide along the bore from its first flow control position to its second flow control position.