An autoinjector having a reservoir containing fluid and including: a piston； a piston rod cooperating with the piston and is movable between a rest position and an injection position in which the piston rod has moved the piston to inject the fluid； an actuator spring urging the piston rod towards its injection position； a force-adjustment system exerting at least one force on the piston rod, the force adding to the force exerted by the spring on the piston rod at the beginning of injection； two pivot members cooperating with the piston rod and are connected together by two resilient elements, at least one pivot member being blocked prior to actuation by a locking system, thus preventing the autoinjector from being actuated, and an unlocking element adapted to move and/or to deform the locking system so as to unblock the at least one pivot member.
