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.