Retractable needle safety syringes

A safety syringe 10 includes a barrel 18, plunger assembly 12, and barrel adapter 20. A barrel adapter 20 mountable to a syringe barrel 18 includes a barrel tip 32, needle assembly 42, and needle retraction mechanism 21. The needle assembly 42 includes a needle hub 24, needle seal 26, and needle 29, which is configured to pass-through the needle assembly 42, locking mechanism 22, biasing member 30, and barrel tip 32. The needle retraction mechanism 21 includes a biasing member 30 and locking mechanism 22 such that actuation of the locking mechanism 22 allows the biasing member 30 to cause retraction of the needle 28 into the barrel tip 32. Methods of assembling, manufacturing, and using such syringes 10 are also provided.