A syringe comprising: a barrel having a fluid chamber, an inside surface, a proximal end, a proximal shoulder located on the inside surface, a distal end adapted to be attached to a needle and a ceiling located on the inside surface and adjacent the distal end; and a plunger rod having a distal end and a proximal end, the plunger rod adapted to slidingly engage the inside surface of the fluid chamber, the plunger rod including a hollow outer housing defined by a wall and a hollow inner sleeve slidably receivable within the outer housing and defining a cavity, and a stopper located on the distal end of the plunger rod, the stopper including a distal face and an outer wall surface, characterized in that the outer housing including at least one window extending axially through the wall adjacent the proximal end of the plunger rod, the inner sleeve including at least one flexible finger adapted to be flexed inwardly towards the cavity, the flexible finger including a distal end, a proximal end, a distal facing ramp surface adapted to engage with the shoulder of the barrel and a distal facing edge, the inner sleeve further including a proximal facing stop edge the finger being sized and shaped to be received within the window, the stopper including a distal rib, a proximal rib and a gap region between the ribs located along the outer wall surface, wherein the configuration of the ramp surface and the stopper is such that axial compression of the stopper permits sufficient axial movement of the plunger rod so that ramp surface engages the shoulder of the barrel, causing inward deflection of the fingers and relative movement of the inner sleeve and outer housing and retraction of the needle, whereby the inner sleeve comprises a pair of bosses wherein one of the pair of bosses are offset from a centerline of the inner sleeve, wherein the outer housing includes webbing on the distal end adapted to support the end of the stopper as the stopper is advanced in a distal direction and a needle attached to the distal end of the barrel, the needle attached to a hub including a flange, wherein inner deflection of the fingers permits distal movement of the inner sleeve within the outer housing, causing a cutting element mounted at the distal end of the inner sleeve to cut through the webbing, the stopper and the flange, causing the needle to retract within the barrel. a barrel having a fluid chamber, an inside surface, a proximal end, a proximal shoulder located on the inside surface, a distal end adapted to be attached to a needle and a ceiling located on the inside surface and adjacent the distal end; and a plunger rod having a distal end and a proximal end, the plunger rod adapted to slidingly engage the inside surface of the fluid chamber, the plunger rod including a hollow outer housing defined by a wall and a hollow inner sleeve slidably receivable within the outer housing and defining a cavity, and a stopper located on the distal end of the plunger rod, the stopper including a distal face and an outer wall surface, characterized in that the outer housing including at least one window extending axially through the wall adjacent the proximal end of the plunger rod, the inner sleeve including at least one flexible finger adapted to be flexed inwardly towards the cavity, the flexible finger including a distal end, a proximal end, a distal facing ramp surface adapted to engage with the shoulder of the barrel and a distal facing edge, the inner sleeve further including a proximal facing stop edge the finger being sized and shaped to be received within the window, the stopper including a distal rib, a proximal rib and a gap region between the ribs located along the outer wall surface, wherein the configuration of the ramp surface and the stopper is such that axial compression of the stopper permits sufficient axial movement of the plunger rod so that ramp surface engages the shoulder of the barrel, causing inward deflection of the fingers and relative movement of the inner sleeve and outer housing and retraction of the needle, whereby the inner sleeve comprises a pair of bosses wherein one of the pair of bosses are offset from a centerline of the inner sleeve, wherein the outer housing includes webbing on the distal end adapted to support the end of the stopper as the stopper is advanced in a distal direction and a needle attached to the distal end of the barrel, the needle attached to a hub including a flange, wherein inner deflection of the fingers permits distal movement of the inner sleeve within the outer housing, causing a cutting element mounted at the distal end of the inner sleeve to cut through the webbing, the stopper and the flange, causing the needle to retract within the barrel.