A fluid transfer device (40A; 40B) for use with a drug vial (30A; 30B) and a drug pump cartridge (10A; 10B) for transferring liquid drug contents from the drug vial to the drug pump cartridge, the drug vial having an open topped drug vial bottle sealed by a drug vial stopper and containing a dosage volume of liquid drug contents for administration purposes, the drug pump cartridge having an open ended cartridge tube having a leading cartridge end, a cartridge septum sealing the leading cartridge end, a slidable driving plunger distanced from the cartridge septum for sealing a maximal dosage volume equal to or greater than the dosage volume of liquid drug contents, the fluid transfer device comprising: (a) a dual open ended barrel having a longitudinal barrel centerline and a transverse partition partitioning said dual open ended barrel into a drug vial port fortelescopically mounting on the drug vial and an open ended piston cylinder, said partition having a dual lumen drug vial stopper puncturing cannula extending into said drug vial port for puncturing the drug vial stopper on said telescopic mounting said drug vial port on the drug vial, said dual lumen drug vial stopper puncturing cannula including a liquid lumen and an air lumen; and (b) a piston head slidingly mounted in said open ended piston cylinder to seal a compression chamber with said transverse partition, said compression chamber being in flow communication with said air lumen, said piston head having a drug pump cartridge port for telescopically mounting on the leading cartridge end, said drug pump cartridge port including a major cartridge septum puncturing cannula and a minor cartridge septum puncturing cannula for puncturing the cartridge septum on said telescopic mounting said drug pump cartridge port on the leading cartridge end, said major cartridge septum puncturing cannula being in sealed flow communication with said liquid lumen for liquid transfer between the drug vial and the drug pump cartridge, said minor cartridge septum puncturing cannula venting the drug pump cartridge on said telescopic mounting said drug pump cartridge port on the leading cartridge end, the fluid transfer device having an initial set-up position in which said piston head is spaced apart from said transverse partition for trapping air in said compression chamber and a final filling position in which said piston head is slidingly inserted towards said transverse partition along an insertion stroke for urging said trapped air into the drug vial for urging the drug vial's dosage volume of liquid drug contents into the drug pump cartridge without displacing the slidable driving plunger. (a) a dual open ended barrel having a longitudinal barrel centerline and a transverse partition partitioning said dual open ended barrel into a drug vial port fortelescopically mounting on the drug vial and an open ended piston cylinder, said partition having a dual lumen drug vial stopper puncturing cannula extending into said drug vial port for puncturing the drug vial stopper on said telescopic mounting said drug vial port on the drug vial, said dual lumen drug vial stopper puncturing cannula including a liquid lumen and an air lumen; and (b) a piston head slidingly mounted in said open ended piston cylinder to seal a compression chamber with said transverse partition,