The invention refers to an auto-
injector (1) and to a method for operating it, the auto-
injector comprising: - a tubular
chassis (2), - a carrier subassembly comprising a tubular carrier (7) slidably arranged in the
chassis (2), the carrier (7) containing a
syringe (3) with a hollow injection needle (4), a drive spring (8) and a
plunger (9) for forwarding load of the drive spring (8) to a stopper (6) of the
syringe (3), - a wrap-over trigger sleeve (12) arranged over the distal end (D) of the auto-
injector (1), the trigger sleeve (12) extending at least almost over the whole length of the auto-injector (1), - a control spring (19) arranged around the carrier (7), - first
interlock means (20, 22, 23, 24) for
coupling a proximal end of the control spring (19) to either the carrier (7) for advancing it for
needle insertion or to the
chassis (2) for needle retraction, - second
interlock means (11, 13, 15) arranged for releasing the drive spring (8) for injection, - third
interlock means (16, 17, 18) arranged for
coupling the chassis (2) to the carrier (7) for joint axial translation relative to the trigger sleeve (12), - fourth interlock means (21, 25, 26, 28) arranged for
coupling a distal end of the control spring (19) to either the carrier (7) for needle retraction or to the trigger sleeve (12) otherwise.