Abstract: Syringe having a plunger, a barrel and a restrictor mechanism between the shaft of the plunger and the barrel and including a first part engaged with the barrel for limiting movement of the first part with respect to the barrel in a first direction, and a second part. The restrictor mechanism and/or plunger shaft carries a formation for limiting movement of the restrictor mechanism with respect to the plunger in the first direction. The restrictor mechanism as a further member which restricts movement of the restrictor mechanism with respect to the barrel or plunger shaft in a second direction. A latch member prevents he further member from restricting movement of the restrictor mechanism with respect to the barrel or plunger shaft in the second direction until a predetermined point in an operation cycle of the syringe.

Abstract: A disposable syringe (2) is disclosed. Withdrawal of a plunger handle (18) in the direction of arrow B to fill the syringe causes a moveable safety bobbin (20) to lock, and shaft (16) slides in the direction of arrow B relative to safety bobbin (20) and washer (22). Subsequent depression of plunger handle (18) in the direction of arrow A causes safety bobbin (20) to move along barrel (4), from which position it can not be withdrawn. This therefore prevents subsequent withdrawal of piston (14) and therefore prevents re-use of the syringe.