Abstract: A syringe for injecting medicament having automatic needle extension and retraction the syringe includes a first body with a cylindrical cross-section, which includes a front end and a rear end. The front end is provided with a means of transport smaller in diameter than the first body, which is fastened to same with a first fastening protrusion. The means of transport include a male frustoconical element which in turn includes conduits to transport said medicament, the front end further including a sealing protrusion and, located above said first fastening protrusion and said first sealing protrusion, a first alignment protrusion, inside said first body there is also a first elastic element which is fastened to said rear end of said first body with a posterior spring clip, and to said means of transport with an anterior spring clip, the rear end of said first body includes a handle.

Abstract: A needle-extension and retraction device for a syringe for collecting blood samples provided with a vacuum tube includes a needle having a front and rear part. The syringe includes a front portion of a reduced diameter, and a rear portion of a greater diameter, in which the said vacuum tube is housed. The extension and retraction mechanism includes a resilient front member, which further includes a resilient rear member. The resilient front member has a resilient return constant that is slightly less than that of the said rear resilient member. A fastening member having a front end and a rear end is disposed between the resilient front member and the resilient rear member. A sealing member that includes a front face and a rear face, is disposed about the rear resilient return element. The device also includes an actuator means disposed on the rear portion of the syringe.