An injection device (210) comprising: a housing (212) adapted to receive a syringe (214) having a discharge nozzle (218), the housing including means (226) for displacing the syringe from an extended position in the that the discharge nozzle extends from the housing to a retracted position in which the discharge nozzle is contained within the housing； an actuator (230)； first and second drive elements (232, 234), of which the first acts on the actuator and in turn acts on the second, the second acts on the syringe to discharge its contents through the discharge nozzle, the first drive element being capable of movement with respect to the second when the actuator acts on the first and the second is retained by the syringe； and of the actuator and the first drive element, one comprises a flexible arm (233) which is displaced towards a position where it engages with a drive surface in the other, allowing the actuator to act on the first drive element and preventing the first it moves with respect to the last one, the flexible arm being mobile against its displacement under the action of the actuator to disengage the flexible arm from the driving surface； characterized in that: the second driving element comprises a stop (270) that prevents the flexible arm from decoupling from the driving surface until the first driving element has been advanced to a position of nominal release with respect to the second driving element, whereby the flexible arm disengages from the driving surface, allowing the actuator to move relative to the first driving element, and thereby releasing the syringe from the action of the actuator, whereby the displacement means returns the syringe to its retracted position .Un dispositivo de inyección (210) que comprende: una carcasa (212) adaptada para recibir una jeringuilla (214) que tiene una boquilla de descarga (218), la carcasa incluyendo medios (226) para desplazar la jeringuilla desde una posición extendida en la que la boquilla de descarga s
