The invention relates to an autoinjector comprising a body (1； 1010) that receives a barrel, such as a pre-filled syringe (A). The autoinjector comprises a plunger rod (5； 1005) which can engage with the plunger of the barrel and which can be moved between a loaded position and an injection position. An injection spring (8； 1008) is provided to push the plunger rod (5； 1005) into the injection position. The autoinjector also comprises an injection lock which locks the plunger rod (5； 1005) in the loaded position and which comprises a control sleeve (4； 1004), said control sleeve (4； 1004) containing the plunger rod (5； 1005) and the injection spring (8； 1008). The plunger rod (5； 1005) comprises a radial recess (50； 1050) that receives at least one substantially spherical locking element (7； 1007) that can move between a locking position and an unlocking position. The aforementioned at least one locking element (7； 1007) is pushed radially towards the exterior by the plunger rod (5； 1005) and is held in the locking position by a locking member (23； 1004) which can be moved in relation to the plunger rod (5； 1005) in order to release the at least one locking element (7； 1007) and, in this way, unlock the injection lock, thereby allowing the injection spring to move the plunger rod (5； 1005) into the injection position.Autoinjecteur comportant un corps (1； 1010) recevant un réservoir, tel qu'une seringue pré-remplie (A), ledit autoinjecteur comportant une tige de piston (5； 1005) adaptée à coopérer avec le piston dudit réservoir, ladite tige de piston (5； 1005) étant déplaçable entre une position chargée et une position d'injection, un ressort d'injection (8； 1008) étant prévu pour solliciter ladite tige de piston (5； 1005) vers sa position d'injection, l'autoinjecteur comportant une serrure d'injection qui bloque ladite tige de piston (5； 1005) dans sa position chargée, ladite serrure d'injection comportant un manchon de commande (4； 1004), ledit manchon de commande
