Cartridge-free, multi-dose injection apparatus

An injection apparatus (20) multidose without cartridge comprising: an outer housing (22) including a tubular body (24), said body defining the outer shell a hollow interior having a proximal end (26) and a distal end ( 28); A multidose amount of medicine (32) within a distal end portion of said external housing and sealed between a movable piston (34) and septum (36); a drive member (64) extending within said hollow interior of said piston support; one, external to said housing, a manual actuator (60) as dosing button for setting the dose to be injected; a mechanical drive assembly (62) extending within the proximal end portion of said outer housing and is operatively connected to said dosing button being operable said drive assembly mechanically by shifting said dosage knob from a first position to a second position, being able to operate said mechanical drive assembly to cause said drive member advancement in the distal direction to shift said piston distally for dispensing a dose of medicine through an opening in said septum; wherein said external housing body, along at least a portion of its periphery, has a construction plastic one-piece extending from said proximal end to said distal end; wherein said piston slides within said hollow interior in contact, fluid tight, with an internal surface (38) of said external housing body; and wherein at least a majority of the length of said mechanical drive assembly fits within said hollow interior of said external housing body at least when said dosage knob is disposed in said second position.