System for administering a pharmaceutical product from a cartridge (155, 155 '), comprising: an injector body (105, 105', 150 ") having a side wall (110, 110 ') having a proximal end portion (106, 106 '), a distal end portion (107, 107'), an inner surface (120, 120 '), and an outer surface (115, 115'), said inner surface (120, 120 ') defining as said side wall (110, 110 ') a cavity (125, 125') for receiving at least a part of said cartridge (150, 155 ')； one or more retaining elements (135, 135') arranged on said surface external (115, 115 ') of said injector body (105, 105')； a piston rod (130, 130 ', 130 ") having a proximal end part (131, 131') and an end part distal (132, 132 ') and one or more receiving elements (133, 35'), between said proximal end part (131, 131 ') and said distal end part (132, 132'), adapted to engage said retaining elements tion； wherein said one or more retaining elements (135, 135 ') and said one or more receiving elements (133, 35') are constructed to cooperatively retain said piston rod (130, 130 ') adjacent to the external surface (115, 115 ') of said injector body (105, 105') when said piston rod (130,130 ') is in a first position, characterized in that said one or more retaining elements (135, 135') and said one or more receiving elements (133, 35 ') are constructed to cooperatively release said piston rod (130, 130') from said injector body (105, 105 ') when said piston rod transitions axially toward said distal end (107, 107 ') of said injector body to a second position； and why said piston rod (130, 130 ') has a thrust surface (152, 152') to engage said cartridge (155, 155 ') located in said cavity (125, 125') of said injector body (105, 105 '), said thrust surface (152, 152') being constructed to move said cartridge (155, 155 ') axially distally from said first position to said second position to simultaneously activate said cartridge (155, 155 ', 155 "), and a tamper-resistant band (194") having a first part (206') attached to
