A RESETTABLE DRIVE MECHANISM FOR A MEDICATION DELIVERY DEVICE IS DISCLOSED, SAID MECHANISM COMPRISING A HOUSING (13, 17, 40), A DRIVE MEMBER (20) ROTATABLE WITH RESPECT TO THE HOUSING IN A SECOND DIRECTION FOR DELIVERING A DOSE OF A MEDICATION, A PISTON ROD (12) ADAPTED TO BE DRIVEN IN A DISTAL DIRECTION WITH RESPECT TO THE HOUSING BY THE DRIVE MEMBER, WHEN THE DRIVE MEMBER ROTATES IN THE SECOND DIRECTION, A STOP MEMBER (26) ADAPTED TO PREVENT ROTATION OF THE DRIVE MEMBER IN A FIRST DIRECTION OPPOSITE TO THE SECOND DIRECTION WITH RESPECT TO THE HOUSING, WHEN THE STOP MEMBER ENGAGES THE DRIVE MEMBER, AND A CLUTCH MEMBER (58) MOVABLE WITH RESPECT TO THE HOUSING BETWEEN A DELIVERY POSITION (D) AND A RESET POSITION (R), WHEREIN, WHEN THE CLUTCH MEMBER IS IN THE DELIVERY POSITION, THE STOP MEMBER AND THE DRIVE MEMBER ARE ENGAGED AND THE DRIVE MEMBER IS PREVENTED FROM ROTATING IN THE FIRST DIRECTION WITH RESPECT TO THE HOUSING, AND WHEN THE CLUTCH MEMBER IS IN THE RESET POSITION, THE DRIVE MEMBER AND THE STOP MEMBER ARE DISENGAGED, THE DRIVE MEMBER IS ROTATABLE IN THE FIRST DIRECTION WITH RESPECT TO THE HOUSING AND THE PISTON ROD IS MOVABLE IN THE PROXIMAL DIRECTION WITH RESPECT TO THE HOUSING.
