Passive reuse prevention syringe that uses a retaining ring lock

A syringe assembly, comprising:

• a syringe barrel having an inside surface defining a chamber, an open proximal end, a distal end, and an outlet disposed adjacent the distal end in fluid communication with the chamber;
• a plunger assembly disposed at least partially within the syringe barrel, comprising an elongate plunger rod and a plunger head having a distal sealing surface and a proximal end surface, the proximal end surface of the plunger head having a continuous perimeter and the plunger rod and the plunger head being integrally connected;
• and
• a retaining ring lock disposed on the inside surface of the barrel and extending into the chamber of the barrel and defining an engagement surface about a perimeter of the chamber of the barrel, the retaining ring lock adapted to engage and retain the plunger head in a locked position at least partially within the chamber of the barrel,
• wherein the engagement surface of the retaining ring lock engages the continuous perimeter of the proximal end surface of the plunger head in a perimetrical engagement when the plunger head is in the locked position, and
• wherein the plunger assembly is formed as a single, monolithic piece.