The invention relates to an auxiliary
injection device (1) for injecting components contained in a medical container (40), comprising: - a body (10) adapted to receive the medical container (40) in a
fixed position relative to the body (10), the body (10) being configured to be held in the hand of a user, - a spring-loaded
piston rod (30) capable of translational movement within the body (10) between a proximal
rest position and a distal operating position, in which distal operating position the
piston rod (30) engages and pushes against a stopper (44) in the medical container (40), - a blocking
system comprising a locking member (50, 60, 70) configured to engage the
piston rod, the locking member being movable between a locking position, in which the locking member holds the
piston rod (30) in the proximal
rest position, and a release position, in which the locking member allows the
piston rod (30) to move from the proximal
rest position to the distal operating position under the force of a spring (31), wherein the
piston rod (30) comprises a proximal end (32) extending out of the body (10) and configured to be pushed in a distal direction by the user when the locking member (50, 60, 70) is in the release position to accelerate the movement of the piston rod (30) to the distal operating position.