An injection device for injecting an injectable substance, the injection device comprising a housing having an interiorly facing wall with the wall having a plurality of ribs formed thereon, the ribs defining a channel extending therebetween, a plunger rod mountable within the housing and having at least one protrusion engageable within the channel, a vial containing the injectable substance, a spring mounted at the distal end of the housing with the spring being biased between the distal end and the needle hub, and a pusher rod raised such that pressure thereon from the plunger rod will cause the pusher rod to push the injectable substance into the hollow needle for injection, the pressure causing the spring to act on the needle hub to move the needle hub and vial upwardly within the housing such that the needle is an enclosed position within the housing and cannot be reused.
