An autoinjector comprising: a front case (2.1) having a first rib (2.1.2) and a second rib (2.1.3); a rear case (2.2) telescopically coupled to the front case (2.1), the rear case (2.2) having latch arms (2.2.1) adapted to engage the first rib (2.1.2) and the second rib (2.1.3), wherein, when the front case (2.1) is in a first position relative to rear case (2.2), the latch arms (2.2.1) are engaged to the first rib (2.1.2), and wherein, when the latch arms (2.2.1) disengage the first rib (2.1.2), the front case (2.1) translates to a second position relative to the rear case (2.2), and the latch arms (2.2.1) engage the second rib (2.1.3), characterized in that a) the auto-injector comprises a syringe having a needle retraction mechanism, the syringe including an inner plunger telescopically arranged on an outer plunger, wherein a distal end of the inner plunger is coupled to a stopper of the syringe, and a plunger spring biases the outer plunger relative to the inner plunger, wherein the stopper includes a cavity (5.1) adapted to engage a needle mount; in that b) the auto-injector further comprises a drive carriage disposed in the rear case (2.2) and adapted to engage the inner plunger on the syringe; and a drive spring adapted to apply a force to the drive carriage relative to the rear case (2.2), and in that c) in the second position the front case (2.1) and the rear case (2.2) move axially apart relative to the first position and a syringe forward latch abuts a shoulder (14.1)on a carrier, creating space allowing the inner plunger with the stopper coupled to the needle mount to move axially in a proximal direction to withdraw the needle into a barrel of the syringe. a front case (2.1) having a first rib (2.1.2) and a second rib (2.1.3); a rear case (2.2) telescopically coupled to the front case (2.1), the rear case (2.2) having latch arms (2.2.1) adapted to engage the first rib (2.1.2) and the second rib (2.1.3), wherein, when the front case (2.1) is in a first position relative to rear case (2.2), the latch arms (2.2.1) are engaged to the first rib (2.1.2), and wherein, when the latch arms (2.2.1) disengage the first rib (2.1.2), the front case (2.1) translates to a second position relative to the rear case (2.2), and the latch arms (2.2.1) engage the second rib (2.1.3), a) the auto-injector comprises a syringe having a needle retraction mechanism, the syringe including an inner plunger telescopically arranged on an outer plunger, wherein a distal end of the inner plunger is coupled to a stopper of the syringe, and a plunger spring biases the outer plunger relative to the inner plunger, wherein the stopper includes a cavity (5.1) adapted to engage a needle mount; in that b) the auto-injector further comprises a drive carriage disposed in the rear case (2.2) and adapted to engage the inner plunger on the syringe; and a drive spring adapted to apply a force to the drive carriage relative to the rear case (2.2), and in that c) in the second position the front case (2.1) and the rear case (2.2) move axially apart relative to the first position and a syringe forward latch abuts a shoulder (14.1)on a carrier, creating space allowing the inner plunger with the stopper coupled to the needle mount to move axially in a proximal direction to withdraw the needle into a barrel of the syringe.