A DRIVE MECHANISM FOR USE IN A DRUG DELIVERY DEVICE (1) COMPRISING: A HOUSING (3, 7)； A DRIVE MEMBER (14) MOVABLE LONGITUDINALLY AND NON-ROTATABLE WITH RESPECT TO THE HOUSING； A PISTON ROD (10) THAT IS NON-ROTATABLE WITH RESPECT TO THE HOUSING； A ROTATING MEANS (13) RELEASABLY ENGAGED WITH THE PISTON ROD AND ENGAGED TO THE DRIVE MEMBER AND ENGAGED TO THE HOUSING WHEREIN THE ROTATING MEANS IS SELECTED FROM THE GROUP OF (I) TO (III), (I) A CARRIER PLATE (28) HAVING PAWL ARMS (29) AND A GEAR (27), (II) A CARRIER PLATE HAVING PAWL ARMS AND A LEVER (427), (III) A LEVER ASSEMBLY. WHEN THE DRIVE MEMBER MOVES PROXIMALLY WITH RESPECT TO THE HOUSING THE ROTATING MEANS MOVES PROXIMALLY WITH RESPECT TO THE PISTON ROD, AND WHEN THE DRIVE MEMBER MOVES DISTALLY THE ROTATING MEANS MOVES DISTALLY DISPLACING THE PISTON ROD TOWARDS THE DISTAL END OF THE DEVICE.
