A single use syringe (20) and a plunger rod locking device (60) for such a syringe are provided. The locking device and plunger rod (30) include features that cause the plunger rod to be locked with respect to the syringe barrel (22) upon completion of an injection stroke. A cutting member (87) is provided at the distal end of the locking device. The cutting member will penetrate, and thereby disable the stopper (44) affixed to the plunger rod in an attempt to retract the plunger rod following the injection stroke. The locking device includes barbs (76) for engaging the syringe barrel.
