Patent ID: 7900658

Claim:
A method of withdrawing a prescribed amount of drug from a drug vial in an automated manner comprising the steps of: identifying the type of drug vial being used; accessing a database to retrieve one or more stored vial characteristics that are associated with the identified drug vial; positioning a vented needle relative to the drug vial based on the stored vial characteristics such that in a first mode of operation, a vent port of the vented needle is open and the drug vial is vented to atmosphere and in a second mode of operation, the vent port is closed; and drawing the prescribed amount of drug from the drug vial, wherein the stored vial characteristics include information about the dimensions of a septum of the drug vial through which the vented needle is inserted to access an interior chamber of the drug vial and the step of positioning the vented needle comprises the steps of: retrieving a thickness of the septum from the stored septum dimensions; and calculating a position of the vented needle in the first mode of operation where both an open tip of the vented needle and the vent port clear the septum and are located in the interior chamber and calculating a position of the vented needle in the second mode of operation where only the open tip end clears the septum and is located in the interior chamber.