A syringe assembly comprising: a fluid barrel (110, 410) including a sidewall having an inside surface defining a fluid chamber for retaining fluid and having a first cross-sectional width, an open proximal end and a distal end including a distal wall; a plunger rod (160, 460) disposed within the fluid chamber comprising a distal end, a proximal end, a plunger rod body extending from the distal end to the proximal end, and a stopper disposed at the distal end of the plunger rod for forming a fluid-tight seal with the inside surface of the barrel (110, 410); a retraction barrel (120, 420) disposed adjacent to the sidewall of the fluid barrel, the retraction barrel (120, 420) including a wall having an interior surface defining a needle chamber, an open proximal end, an open distal end including a barrier wall, an aperture between the wall of the retraction barrel (120, 420) and the sidewall of the fluid barrel (110, 410) permitting fluid communication between the fluid chamber and the needle chamber and a needle hub assembly comprising a needle hub, a needle cannula attached to the needle hub, the needle cannula being in fluid communication with the aperture and biased to move in a proximal direction; and a trigger element (190, 490) disposed within the retraction barrel (120, 420) and moveable within the retraction barrel (120, 420) independently from the plunger rod (160, 460), the trigger element (190, 490) including a distal end, a proximal end (199, 499) and a trigger element body (192, 492), the trigger element body (192, 492) extends from the distal end to the proximal end (199, 499), a snap element disposed adjacent to the proximal end (199, 499) of the trigger element (190, 490), the snap element having a radially outward extension that extends from the trigger element body (192, 492) and upon engagement with the reaction barrel prevents movement of the trigger element (190, 490) in the distal direction, the trigger element (190, 490) providing a trigger force causing the needle cannula to retract into the reaction barrel (120, 420), characterised in that the plunger rod (160, 460) having a contacting surface; and the snap element being located between the trigger element (190, 490) and the plunger rod (160,460) and having a height that increases from the proximal end to the distal end and wherein a distal end of the snap element is perpendicular to the trigger element body (192, 492), the snap element being adapted to deflect after contact with the contacting surface of the plunger rod so that the trigger element (190, 490) is adapted to be moved in the distal direction. a fluid barrel (110, 410) including a sidewall having an inside surface defining a fluid chamber for retaining fluid and having a first cross-sectional width, an open proximal end and a distal end including a distal wall; a plunger rod (160, 460) disposed within the fluid chamber comprising a distal end, a proximal end, a plunger rod body extending from the distal end to the proximal end, and a stopper disposed at the distal end of the plunger rod for forming a fluid-tight seal with the inside surface of the barrel (110, 410); a retraction barrel (120, 420) disposed adjacent to the sidewall of the fluid barrel, the retraction barrel (120, 420) including a wall having an interior surface defining a needle chamber, an open proximal end, an open distal end including a barrier wall, an aperture between the wall of the retraction barrel (120, 420) and the sidewall of the fluid barrel (110, 410) permitting fluid communication between the fluid chamber and the needle chamber and a needle hub assembly comprising a needle hub, a needle cannula attached to the needle hub, the needle cannula being in fluid communication with the aperture and biased to move in a proximal direction; and a trigger element (190, 490) disposed within the retraction barrel (120, 420) and moveable within the retraction barrel (120, 420) independently from the plunger rod (160, 460), the trigger element (190, 490) including a distal end, a proximal end (199, 499) and a trigger element body (192, 492), the trigger element body (192, 492) extends from the distal end to the proximal end (199, 499), a snap element disposed adjacent to the proximal end (199, 499) of the trigger element (190, 490), the snap element having a radially outward extension that extends from the trigger element body (192, 492) and upon engagement with the reaction barrel prevents movement of the trigger element (190, 490) in the distal direction, the trigger element (190, 490) providing a trigger force causing the needle cannula to retract into the reaction barrel (120, 420),