Needle capture retractable needle safety syringes

A retractable syringe comprising:

• a barrel;
• a plunger;
• and
• a retractable needle assembly comprising:
• a needle retainer comprising at least one flexible arm;
• a needle seal;
• and
• a cannula that defines a hollow core, the cannula engaged with the needle seal and comprising:
• a delivery tip comprising at least one delivery aperture,
• a proximal end comprising at least one inlet aperture to the hollow core, the inlet aperture in fluid communication with the at least one delivery aperture, and
• at least one projection distal to a proximal tip of the proximal end of the cannula and engageable by the plunger,
• the at least one inlet aperture of the proximal end of the cannula being located distally of the at least one projection and proximally and substantially adjacent to the needle seal,
• the at least one flexible arm of the needle retainer configured to releasably engage the cannula, the needle seal disposed proximally of the needle retainer and configured to seal against an inner wall of the barrel, the needle retainer retaining the cannula such that the cannula and the needle seal remain in a substantially fixed position within the barrel during distal translation of the plunger,
• the plunger configured to push fluid distally toward the inlet aperture and to contact the needle seal at an end of the distal translation, and the at least one flexible arm of the needle retainer configured to flexibly disengage from the cannula to permit retraction of the cannula.