Multi-stage injection device

An injection device configured to administer a medicament from a syringe having a syringe barrel at least partially filled with the medicament and sealed by a piston, a flange extending radially from a proximal end of the syringe barrel, and a needle extending distally from a distal end of the syringe barrel, the injection device comprising:

• a lower housing;
• a spring retaining sleeve supported by the lower housing;
• a syringe spring at least partially received within the spring retaining sleeve, wherein the syringe spring is configured to support an underside of the flange of the syringe when installed to support the syringe within the lower housing such that the needle protrudes from a distal end of the lower housing;
• a needle guard in sliding engagement with the lower housing, the needle guard being movable relative to the lower housing in a proximal direction from:
• a first position in which a distal end of the needle guard extends beyond the distal end of the lower housing, the distal end of the needle guard is spaced from a proximal end of the lower housing by a first interval, and the distal end of the needle guard is configured to conceal a distal tip of the needle when the syringe is installed in the lower housing,
• to a second position in which the distal end of the needle guard is spaced from the proximal end of the lower housing by a second interval that is less than the first interval;
• a needle guard spring configured to engage the lower housing and the needle guard to bias the needle guard distally relative to the lower housing;
• and
• an upper housing in sliding engagement with the lower housing and movable relative to the lower housing in a distal direction from a pre-use position to a dispensed position, wherein:
• proximal movement of the needle guard from the first position to the second position is configured to extend the distal tip of the needle distally beyond the needle guard by a first distance when installed, and
• subsequent distal movement of the upper housing relative to the lower housing from the pre-use position toward the dispensed position is configured to (i) first compress the syringe spring, and, in turn, distally translate the needle relative to the lower housing when installed, such that the distal tip of the needle extends distally beyond the needle guard by a second distance that is greater than the first distance, and (ii) thereafter, further advance the upper housing distally relative to the syringe when installed to dispense the medicament from the syringe.