The drive mechanism is suitable for a permanent delivery of a drug from a compact drug delivery device, which may be carried on the body. The drive mechanism comprises a flexible advance cable bearing a coupling feature of longitudinal extension. The advance cable is guided by a guide means. A drive means engages the coupling feature and thus enables an advancement of the advance cable according to the guide means. An end piece is provided to push a plug or bung of a cartridge containing a drug, and the end piece is driven by the advance cable. The drive means is permanently engaged with the coupling feature. This allows a permanent advancement of the plug or bung by means of the drive mechanism.
