A system for mixing or reconstituting a drug contained in a first container with a diluent or fluid contained in a second container. The second container has a port docking assembly for engaging the first container. The first container is rotatable and axially slidable within the port docking assembly. The port docking assembly has an actuator to urge a stopper fluidly sealing the first container into the interior of the first container. The port docking assembly further includes a movable plug constructed to fluidly seal the second container in a first, docked position and to provide access to the interior of the second container in a second, activated position, whereby fluid communication between the first and second containers is provided when the first and second containers are in the second, activated position.