Abstract: A restricted use hypodermic syringe employs a plunger assembly which enables it to be filled and used conventionally but not reused. The plunger assembly incorporates a plunger lock positioned in the syringe barrel about the plunger rod. The plunger lock engages the inner wall of the barrel to form a one-way brake which allows movement of the plunger lock forwardly in the barrel but prevents its rearward movement. The plunger lock also engages the plunger rod to form a one-way clutch which allows the plunger rod to move rearwardly relative to the plunger lock and couples the plunger rod and plunger lock for movement together in the forward direction. The syringe is provided to the user with the piston of the plunger assembly positioned forwardly and the plunger lock positioned rearwardly in the syringe barrel. The syringe is filled by withdrawing the piston.

Abstract: A restricted use hypodermic syringe employs a plunger assembly which enables it to be filled and used conventionally but not reused. The plunger assembly incorporates a plunger lock positioned in the syringe barrel about the plunger rod. The plunger lock engages the inner wall of the barrel to form a one-way brake which allows movement of the plunger lock forwardly in the barrel but prevents its rearward movement. The plunger lock also engages the plunger rod to form a one-way clutch which allows the plunger rod to move rearwardly relative to the plunger lock and couples the plunger rod and plunger lock for movement together in the forward direction. The syringe is provided to the user with the piston of the plunger assembly positioned forwardly and the plunger lock positioned rearwardly in the syringe barrel. The syringe is filled by withdrawing the piston.