The invention relates to a disposable injector with a housing (10) in which arearranged at least one mechanical spring energy reservoir (50), at least one cylinder/pistonunit (100), at least one piston-actuating ram (60), and at least one trigger unit.The housing comprises at least one compression hook (21) which, in the area ofits free end, has at least one bearing surface. The piston-actuating ram lieson the bearing surface. The locking state of the compression hook is secured bya trigger element positioned in a locking position. The trigger element has alocking position in which it bears on a closure cap (120). The trigger elementhas a release position which brings about a lateral retreat of the compressionhook.
