Pre-filled syringe safety devices and injectors, systems, and methods of use

An injector for use with a syringe having a plunger, a barrel having a flange, and a needle, the injector comprising:

• a cartridge configured to support the syringe therein;
• a casing including a casing distal opening, an internal volume, a sidewall, an inner surface, a track defined on the inner surface, and a slider opening extending through the sidewall, the cartridge supported within the casing, wherein, when the cartridge supports the syringe therein, the flange of the syringe engages with a portion of the casing to support the barrel of the syringe is in a fixed position relative to the casing such that movement of the barrel relative to the casing in a distal-proximal direction is prevented;
• a tube including a tube distal end, the tube slidably engaged with the cartridge and biased so the tube distal end extends distally past a tip of the needle and distally past the casing distal opening in an extended state of the tube, the tube configured to retract proximally upon overcoming a biasing force such that the needle of the syringe extends beyond the tube distal end and the casing distal opening in a retracted state of the tube, the tube being biased to reextend and lock in the extended state following being in the retracted state;
• and
• a plunger slider having a first portion configured to engage with the plunger of the syringe within the internal volume of the casing, the plunger slider having a second portion extending from the first portion through the slider opening and positioned at least partially outside the casing, the second portion being depressible by a user in order to depress the plunger of the syringe,
• wherein the tube is in sliding relation to the cartridge, and wherein a biasing member is operably coupled between the tube and the cartridge, and
• wherein the tube is in engagement with the track and the tube is configured to lock in the extended state.

A method of injecting a substance into an injection site of a patient, the method comprising:

• positioning a distal tube of an injector adjacent the injection site of the patient, the injector comprising:
• a casing having an opening at a distal end thereof, a sidewall, a slider opening extending through the sidewall, an inner surface, and a track defined on the inner surface;
• a cartridge housed within the casing and supporting a syringe therein, the syringe enclosing the substance therein and including a barrel, a needle, and a plunger;
• a plunger slider engaged with the plunger of the syringe and extending through the slider opening;
• the distal tube being slidingly coupled with the cartridge and biased into an extended position such that the distal tube extends over the needle and at least partially outwards from the opening at the distal end of the casing, wherein movement of the plunger slider is independent of movement of the distal tube;
• depressing the distal tube against the injection site of the patient thereby causing the distal tube to be in a retracted position wherein the needle protrudes past the distal tube and into the injection site of the patient;
• distally advancing the plunger slider relative to the casing so as to depress the plunger within the barrel of the syringe to dispense the substance from the barrel, through the needle, and into the injection site of the patient, wherein the barrel of the syringe is in a fixed position relative to the casing and remains in the fixed position before, during, and after depression of the plunger of the syringe;
• and
• retracting the distal tube from the injection site of the patient thereby causing the distal tube to lock in the extended position.