An automatic injection syringe that is pre-loaded with medicament and protected from inadvertent ejection of said medicament or injection of air. A plunger assembly is first positioned with a compressed spring in between a plunger and a retainer element. The compressed spring is held in place by a resilient retainer sleeve and the plunger is inside the syringe tube. When the syringe is pushed back, the resilient retainer sleeve releases the spring which then expands to push the plunger into the reservoir of the syringe tube to eject the medicament out from a syringe needle.
