Abstract: A system for injection includes a syringe body having proximal and distal ends and defining a syringe interior, a stopper member disposed in the syringe interior, a needle hub assembly coupled to the syringe body at the distal end thereof, and a plunger member coupled to the stopper member and configured to be manipulated to insert the stopper member distally in the syringe interior relative to the syringe body and the needle hub. The plunger member includes a plunger body defining a plunger interior, a retraction member disposed in the plunger interior, and a spring disposed in the plunger interior. The retraction member includes a catch-latch and a trigger movably disposed in the catch-latch along a longitudinal axis thereof. The trigger defines a proximal radial extension, a distal radial extension, and an annular trough between the proximal and distal radial extensions.

Abstract: An injection system includes an injection system body defining a proximal opening at a proximal end thereof and a distal needle interface at a distal end thereof. The system also includes a stopper member and a fenestrated separator disposed in the injection system body, forming a proximal drug chamber between the stopper member and the fenestrated separator and a distal drug chamber between the fenestrated separator and the distal end of the injection system body. The system further includes a plunger member configured to be manipulated to insert the stopper member relative to the injection system body. The fenestrated separator forms an openable barrier between the proximal and distal drug chambers. The fenestrated separator is configured to allow flow from the proximal drug chamber to the distal drug chamber with increased pressure in the proximal drug chamber relative to the distal drug chamber.