Passive reuse prevention syringe that uses a flange lock

A syringe assembly includes a syringe barrel having an inside surface defining a chamber, an open proximal end, a distal end, and an outlet; a plunger assembly disposed at least partially within the syringe barrel, including an elongate plunger rod having a locking flange formed thereon; and a plunger head having a distal sealing surface, the plunger rod being engageable with the plunger head such that the plunger rod is adapted to move the plunger head within the chamber of the syringe barrel through an injection cycle; and a flange lock disposed at the open proximal end of the barrel. The flange lock is integral with the open proximal end of the syringe barrel. During the injection cycle, the flange lock engages the locking flange of the plunger rod so as to prevent removal of the plunger rod from the syringe barrel.