A syringe assembly includes a syringe barrel that bounds a compartment extending between a proximal end and an opposing distal end. A stopper is movably disposed with the compartment of the syringe barrel. A plunger rod includes a shaft having a proximal end and an opposing distal end and a plurality of teeth disposed on the shaft, the distal end of the shaft being secured to the stopper. A backstop includes a base coupled to the syringe barrel; a first wing and a second wing secured to the base so as to be at least partially disposed on opposing sides of the base; and a first arm projecting from the first wing. The first wing is movable between a first position where an engaging portion of the first arm engages with the plunger rod and a second position wherein the first arm is spaced apart from the plunger rod.