The present invention relates to an assisted injection device (1) for injecting a composition contained in a medical container (30), comprising: - a body (10) configured to receive the medical container (30) in a fixed position relative to the body (10), - a spring-loaded piston rod (40) translationally movable inside the body (10) along a spring axis (A), between a proximal rest position and a distal operative position wherein the piston rod (40) engages a stopper (34) of the medical container (30) and pushes the stopper (34) in the medical container (30), - a lever (50) pivotably mounted on the body (10) about a first pivot axis (B) orthogonal to the spring axis (A) at a first distance from the spring axis (A), comprising an actuation zone (51) opposite the first pivot axis (B) relative to the spring axis (A), at a second distance from the spring axis (A), - a selective blocking system (60) coupled to the lever by a second pivot axis (C) orthogonal to the spring axis (A), the lever (50) being pivotable between a rest position wherein the selective blocking system (60) engages the piston rod (40) to prevent any translational movement of the piston rod (40) and a second position wherein the selective blocking system (60) releases the piston rod (40) to allow the piston rod (40) to move toward the distal operative position under the spring force.La présente invention concerne un dispositif d'injection assisté (1) pour l'injection d'une composition contenue dans un récipient médical (30), comprenant : - un corps (10) configuré pour recevoir le récipient médical (30) dans une position fixe par rapport au corps (10), - une tige de piston chargée par un ressort (40) mobile par translation à l'intérieur du corps (10) le long d'un axe de ressort (A), entre une position de repos proximale et une position de fonctionnement distale, la tige de piston (40) engageant un dispositif d'arrêt (34) du récipient médical (30) et poussant le dispositif d'arrêt (34) dans le récipient mé
