The invention relates to a disposable injector with a housing (10) in which are arranged at least one mechanical spring energy reservoir (50), at least one cylinder/piston unit (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 of its free end, has at least one bearing surface. The piston-actuating ram lies on the bearing surface. The locking state of the compression hook is secured by a trigger element positioned in a locking position. The trigger element has a locking position in which it bears on a closure cap (120). The trigger element has a release position which brings about a lateral retreat of the compression hook.
