A single-use injector is disclosed comprising a housing (10), arranged in which are at least one mechanical spring energy store (50), at least one piston-cylinder unit (100), which can be effectively filled at least for a certain time, at least one piston-actuating ram (60) and at least one triggering unit (80). The spring energy store comprises at least one pre-tensioned spring element. The spring-loaded piston-actuating ram (60) has at least one retaining rod or hook (62), which can be moved transversely, at least in certain regions, and by means of a supporting portion supports the tensioned spring energy store on at least one resting surface of the housing. When actuation occurs, the triggering unit (80) releases the supporting portion to allow it to move away from the resting surface.