An injector includes an injector housing, an activation button assembly movably mounted to the injector housing and operatively connected to the injection needle, and a cartridge door movably mounted to the injector housing between an open position and a closed position. A deflectable interference member engaging the rear end flange of the cartridge has a resting position configured to limit an insertion depth of a cartridge into an interior channel of the cartridge door to a sealed position, wherein the cartridge piercing needle does not fully penetrate a pierceable septum of the cartridge. The cartridge door includes an interior channel having a cartridge mounted therein. The cartridge includes a substance to be dispensed. The substance includes an anti-C5 antibody or antigen binding fragment thereof, and optionally further includes a recombinant human hyaluronidase enzyme. A method of treating a complement associated condition using an injector thereof. A method of dispensing a substance from an injector thereof.