Disclosed is a syringe assembly which includes a barrel with a cylindrical sidewall having an interior surface defining a chamber for retaining fluid, an open proximal end and a distal end with a distal wall having an opening therethrough in fluid communication with the chamber. The assembly includes an elongate plunger rod having a proximal end, a distal end, a stopper-engaging portion located at the distal end of the plunger rod, a thumb press at the proximal end of the plunger rod, and a main body portion extending between the distal and proximal ends of the plunger rod. The assembly also includes a stopper having a proximal end and a distal end. The stopper is attached to the stopper-engaging portion of the plunger rod. The stopper is distally and proximally movable relative to the stopper-engaging portion. The assembly includes a lock for locking the plunger rod in the barrel to prevent reuse of the syringe assembly when the distal end of the stopper is in contact with the distal wall of the barrel and distal force is applied to the thumb press. The assembly further includes means for separating plunger rod from the main body upon application of sufficient proximal force to the plunger rod, and an indicator for indicating that the plunger rod is locked in the barrel.
