Patent ID: 8034044

Claim:
In a closed system that includes a medical device, a first container containing a drug, a second container containing a liquid, a target container, and a pump, a combining and transferring method comprising: placing the first container and the second container in fluid communication with the medical device; combining the liquid and the drug in the first container to form a resultant mixture while effecting a system-level air exchange via an air vent assembly of the medical device such that equilibrium of pressure within at least the first container, the second container, and the medical device is substantially obtained; and activating the pump to effect a transfer of at least some of the resultant mixture from the first container to the target container via a chamber of the medical device, wherein the transfer causes a moveable member within the chamber to move responsive to a level of the resultant mixture in the chamber to a position that restricts air flow into the target container.