The present disclosure relates to an assisted injection device for injecting a composition contained in a medical container. The injection device includes a body configured to receive the medical container in a fixed position relative to the body. The injection device includes a spring-loaded piston rod translationally movable inside the body along a spring axis. The injection device includes a lever pivotably mounted on the body about a first pivot axis orthogonal to the spring axis at a first distance form the spring axis. The injection device includes a selective blocking system coupled to the lever by a second pivot axis orthogonal to the spring axis. The lever is pivotable between a rest position. The selective blocking system engages the piston rod to prevent any translation movement of the piston rod and a second position wherein the selective blocking system releases the piston rod.
