Abstract: A syringe includes a hollow barrel and a hollow plunger extending into the barrel and being axially movable within the barrel, where the plunger includes an end wall that is releasably secured to the plunger at an opening disposed at a distal end of the plunger and is movable to disengage with the plunger distal end opening during use of the syringe to facilitate access to a retraction cavity disposed within the plunger. A needle assembly is secured within and at a distal end of the barrel. The needle assembly includes a needle holder with a connector to secure a needle to the needle holder.

Abstract: A syringe for giving medical injections which has an internal mechanism for retracting the needle into the syringe after the injection has been given and locking the needle and plunger inside the barrel of the syringe to reduce the risk of accidental needle pricks. In one embodiment the needle is retracted by a tension spring into a compartment inside a hollow plunger and in the other embodiment the needle is propelled by a compressed spring into a compartment within the plunger. In both embodiments, the interior of the hollow plunger is hydraulically sealed off by a barrier from the fluid chamber of the syringe to prevent fluid from entering the interior of the hollow plunger.