Barrel adapters for safety syringes include a barrel and a plunger assembly adapted to move within the barrel, a barrel tip adapted to be sealingly engaged with a distal end of the barrel and a needle retraction mechanism barrel having a needle subassembly and an actuator subassembly. The needle subassembly includes a needle, and a needle-over-mold (NOM) through which the needle extends. The needle subassembly is disposed at least partially within the barrel tip, and adapted to move from an injection position in which the needle extends from a distal end of the barrel tip to a retracted position in which the needle is disposed within at least one of the barrel tip or the barrel. The actuator subassembly includes a needle seal, a push-bar, and an actuator surface. The needle retraction mechanism barrel includes a biasing member and an actuable locking arrangement. A syringe includes such barrel adapters.