Disclosed is a disposable injector which includes a housing in which is arranged a helical compression spring and a cylinder/piston unit including a piston and a cylinder having an interior for operatively receiving and being filled and containing at least temporarily an active substance. The injector includes a spring-loaded piston-actuating ram and a triggering unit in operative arrangement therewith. The spring-loaded piston-actuating ram has proximate a central region thereof a ram plate. The spring-loaded piston-actuating ram also has a non-transversely moveable tension bar above the ram plate. The helical compression spring includes a pre-loaded spring element. Part of the piston-actuating ram is operatively arranged between the triggering unit and the piston of the cylinder/piston unit. The helical compression spring is arranged coaxially with a substantial portion of the non-transversely moveable tension bar. The non-transversely moveable tension bar has a throat-like constriction with a supporting surface in the region of the upper end of the non-transversely moveable tension bar. The housing has an elevated intermediate base with monolithic portions thereof being flexurally elastic elements which operatively extend from the elevated intermediate base. The flexurally elastic elements have a locking position. A triggering element operatively secures the flexurally elastic elements in the locking position. The flexurally elastic elements each have an upper bearing surface operatively supporting and contacting the supporting surface of the non-transversely moveable tension bar in the locking position. The flexurally elastic elements have a release position. The operative movement of the triggering element releases the upper bearing surface of each of the flexurally elastic elements from contact with the supporting surface of the non-transversely moveable tension bar. The non-transversely moveable tension bar is released causing the piston to force the active s
