An improved syringe comprises a tube a resilient needle retainer releasably installed therein a needle being threadably installed in the needle retainer a break-away plunger and a sealing means in the form of a multi-pleated bellows secured to the plunger using a retaining element. The break-away plunger may comprise a plunger with four flanges arranged into a cruciform-shaped cross-section, and with each flange further comprising a specially-shaped narrow cut to aid the breaking process, while leaving the plunger with more lateral stability during use. The multi-pleated bellows improves upon standard piston-plunger arrangements, as each of the bellows may seal independently upon an inside surface of the tube. The needle retainer is releasably installed in the tube for use during an injection using a detent, and is restrained relative to the tube, after retraction of the needle during breaking off of the plunger, using a second detent.
