An autoinjector having a body (1010； 2010) receiving a reservoir, a piston, a needle, an actuating 5 sleeve (1011；2011) having a contact end to contact the body of the user and displaceable relative to the body between projected positions, in which the actuating sleeve at least partially projects out of the body receiving a reservoir, and an actuation position, in which the actuating sleeve is axially displaced towards the interior of the body receiving a reservoir. The actuating sleeve is in a first projected position prior to actuation of the autoinjector and in a second projected position after actuation of the autoinjector. The actuating sleeve or the body receives a reservoir having a flexible tab adapted to deform laterally relative to the actuating sleeve and/or relative to the body receiving a reservoir when the actuating sleeve is displaced from its first projected position towards its actuation position then from its return actuation position towards its second projected position.
