A barrel adapter (20, 120) for a delivery syringe (10, 100) having a barrel (18, 118) and a plunger assembly (12, 112) adapted to move within the barrel (18, 118), the barrel adapter (20, 120) comprising: a barrel tip (32, 132) adapted to be sealingly engaged with a distal end of the barrel (18, 118); a needle assembly including a needle (28, 128) and a needle hub (24, 124) through which the needle (28, 128) extends, the needle (28, 128) having a lumen, the needle assembly being disposed at least partially within the barrel tip (32, 132), and the needle (28, 128) being adapted to move from an injection position in which the needle (28, 128) extends from a distal end of the barrel tip (32, 132) to a retracted position in which the needle (28, 128) is disposed within at least one of the barrel tip (32, 132) or the barrel (18, 118); and a needle retraction mechanism, the needle retraction mechanism including a biasing member (30, 130), characterised in that the barrel adapter (20, 120) further comprises a stylet assembly including a stylet (54, 154) and a stylet disc (52, 152), the stylet (54, 154) being axially slidable and at least partially disposed within the needle lumen, the stylet (54, 154) being proximally disposed and spaced from a distal tip of the needle (28, 128) when the needle (28, 128) is in the injection position; and the needle retraction mechanism further includes an actuable locking arrangement, the locking arrangement being disposed to maintain the biasing member (30, 130) in an energized position when the locking arrangement is locked and to release the biasing member (30, 130) when the locking arrangement is actuated, the locking arrangement being actuable by depression of the plunger assembly (12, 112), and the biasing member (30, 130) being disposed to provide relative motion of the needle (28, 128) and stylet (54, 154) from the injection position to the retracted position when the biasing member (30, 130) is released from the energized position. a barrel tip (32, 132) adapted to be sealingly engaged with a distal end of the barrel (18, 118); a needle assembly including a needle (28, 128) and a needle hub (24, 124) through which the needle (28, 128) extends, the needle (28, 128) having a lumen, the needle assembly being disposed at least partially within the barrel tip (32, 132), and the needle (28, 128) being adapted to move from an injection position in which the needle (28, 128) extends from a distal end of the barrel tip (32, 132) to a retracted position in which the needle (28, 128) is disposed within at least one of the barrel tip (32, 132) or the barrel (18, 118); and a needle retraction mechanism, the needle retraction mechanism including a biasing member (30, 130), characterised in that the barrel adapter (20, 120) further comprises a stylet assembly including a stylet (54, 154) and a stylet disc (52, 152), the stylet (54, 154) being axially slidable and at least partially disposed within the needle lumen, the stylet (54, 154) being proximally disposed and spaced from a distal tip of the needle (28, 128) when the needle (28, 128) is in the injection position; and the needle retraction mechanism further includes an actuable locking arrangement, the locking arrangement being disposed to maintain the biasing member (30, 130) in an energized position when the locking arrangement is locked and to release the biasing member (30, 130) when the locking arrangement is actuated, the locking arrangement being actuable by depression of the plunger assembly (12, 112), and the biasing member (30, 130) being disposed to provide relative motion of the needle (28, 128) and stylet (54, 154) from the injection position to the retracted position when the biasing member (30, 130) is released from the energized position.