Dual chamber syringe with retractable needle

A syringe assembly comprising:

• a fluid barrel 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 disposed within the fluid chamber comprising a distal end, a proximal end, a plunger rod body extending from the distal end of the plunger rod to the proximal end of the plunger rod, and a stopper disposed at the distal end of the plunger rod for forming a fluid-tight seal with the inside surface of the fluid barrel;
• a retraction barrel disposed adjacent to the sidewall of the fluid barrel, the retraction barrel 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 and the sidewall of the fluid barrel 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 disposed within the needle chamber and rotatable within the retraction barrel independently from the plunger rod, the trigger element including a trigger guard that prevents premature retraction of the needle cannula, the trigger element providing a trigger force causing the needle cannula to retract into the retraction barrel, the plunger rod including a flat radial ring that deflects the trigger guard so that the trigger element is moved in a distal direction for retracting the needle cannula.