Automatic injection system

An automatic injection device, comprising:

• a housing comprising a proximal end and a distal end;
• a syringe including a needle, a syringe body and a plunger, the syringe being axially moveable within the housing from a first position to a second position that is distal to the first position to move the needle toward the distal end of the housing, and the plunger being axially moveable relative to the syringe body to expel medication from the syringe body through the needle;
• a shuttle coupled to the syringe, the shuttle having a distal surface comprising a shuttle protrusion and a curvilinear surface, the curvilinear surface extending from the shuttle protrusion to define an undercut region;
• and
• a follower having a follower body and a latch, the latch being moveable relative to the follower body and relative to the shuttle protrusion, the latch comprising a latch protrusion, the latch protrusion having a straight leading surface and a curved trailing surface;
• wherein:
• the follower has a coupled configuration in which the latch of the follower is biasedly coupled with the shuttle protrusion to inhibit rotation of the follower, the straight leading surface of the latch protrusion is in contact with the shuttle protrusion, and
• the follower has a decoupled configuration in which the latch protrusion has cleared the shuttle protrusion and the curved trailing surface of the latch protrusion is in sliding engagement with the curvilinear surface of the shuttle as the follower is rotated relative to the shuttle, the shuttle axially moveable toward the proximal end of the housing to retract the syringe after the follower has rotated through a predetermined angle of rotation.