A medical injector system for injecting fluid from a syringe (300) into a patient, the syringe (300) having a barrel (300) and a plunger (310), the plunger (310) comprising an inner surface having an engaging portion (311) adapted to be releasably engaged by a plunger handle (130) which has a retention member (142) adapted to releasably engage the engaging portion (311) of the plunger (310); and a syringe holder comprising a cradle member (200) adapted to receive a barrel (300) of the syringe (300) and a pivotable catch (500) to releasably lock the syringe (300) in the cradle member (200).