A barrel adapter mountable to a syringe barrel includes a barrel tip, a biasing member, a locking mechanism, and a needle assembly. A safety syringe includes a barrel, a plunger assembly, and a barrel adapter. The needle assembly includes a needle, a needle hub, and a needle seal. The needle is configured to pass-through the needle assembly, locking mechanism, biasing member, and barrel tip such that, at one end the needle is within the barrel and at another end the needle passes through an aperture in the barrel tip. The barrel may be substantially cylindrical, having along its longitudinal axis a distal end for drug injection, a proximal end for injection control, and at least a portion of the barrel interior for drug containment. The barrel adapter provides needle retraction mechanisms to the barrel to form a safety syringe. Methods of assembling, manufacturing, and using such syringes are also provided.
