An autoinjector comprising:. a body receiving a reservoir, said reservoir containing fluid and including a piston, such as a pre-filled syringe, said reservoir being stationary in said body,. an actuator sleeve that includes a contact end for coming into contact with the user's body, said actuator sleeve extending inside said body at least in part and being movable relative to said body between projecting positions, in which said actuator sleeve projects out from said body at least in part, and an actuated position, in which said actuator sleeve is moved axially into said body, said actuator sleeve being in a first projecting position before actuation of the autoinjector, and in a second projecting position after actuation of the autoinjector,. a piston rod that is adapted to co-operate with the piston of said reservoir, said piston rod being movable between a primed position and an injection position in which said piston rod has moved the piston of the reservoir so as to inject the fluid into an injection site,. a visual, audible, and/or tactile indicator device for indicating to the user that said autoinjector may be removed from said injection site, said visual, audible and/or tactile indicator device being arranged at the rear end of said body, remote from said injection site, said autoinjector being characterized in that it includes a retarding device so as to delay actuating said visual, audible, and/or tactile indicator device relative to the end of injection, said retarding device comprising an epicyclic gear train having at least one stage, advantageously two stages, said epicyclic gear train comprising a retarding spring, at least one planet carrier (16a, 16b), each carrying at least one planet gear (17a, 17b), a trigger, and a locking key so as to prevent said trigger from turning until the end of injection, said retarding spring being made in the form of a spiral spring that is fastened firstly to a planet carrier that forms an indicator of said visual, audible and/or tactile indicator device, and secondly to the body, said locking key comprising a head, a longitudinal rod, and an endpiece that is adapted to co-operate with the piston rod, wherein, prior to triggering the retarding system, the head of the locking key is in its blocking position in which it co-operates with a corresponding profile of the body and with a corresponding profile of the trigger, such that said trigger is prevented from turning relative to said body by said locking key, wherein when the piston rod arrives towards its end-of-injection position, it co-operates with the endpiece of the locking key so as to pull said locking key axially downwards out from its blocking position, such that said trigger is thus no longer prevented from turning by said locking key.. a body receiving a reservoir, said reservoir containing fluid and including a piston, such as a pre-filled syringe, said reservoir being stationary in said body,. an actuator sleeve that includes a contact end for coming into contact with the user's body, said actuator sleeve extending inside said body at least in part and being movable relative to said body between projecting positions, in which said actuator sleeve projects out from said body at least in part, and an actuated position, in which said actuator sleeve is moved axially into said body, said actuator sleeve being in a first projecting position before actuation of the autoinjector, and in a second projecting position after actuation of the autoinjector,. a piston rod that is adapted to co-operate with the piston of said reservoir, said piston rod being movable between a primed position and an injection position in which said piston rod has moved the piston of the reservoir so as to inject the fluid into an injection site,. a visual, audible, and/or tactile indicator device for indicating to the user that said autoinjector may be removed from said injection site, said visual, audible and/or tactile indicator device being arranged at the rear end of said body, remote from said injection site,