A system including an adapter (14) for sequential engagement with a cartridge (18) containing a first substance and a vial (16) containing a second substance is disclosed. The adapter is configured to first engage with the vial and subsequently engage with the cartridge such that the cartridge is in fluid communication with the vial via the adapter. The system includes a latch member (150) engageable with a portion of the cartridge. A plunger rod (44) includes a protrusion (50) and is adapted to communicate with the latch member, the plunger rod being transitionable from a disengaged position, in which the protrusion of the plunger rod is disengaged from the latch member and the latch member is locked to the cartridge, to an engaged position, in which the protrusion is engaged with the latch member and the latch member is unlocked from the cartridge and locked to the plunger rod.