FIELD : medicine.SUBSTANCE : invention relates to medical equipment, in particular to injection devices for administering a drug. Apparatus comprises : cartridge holder, configured to receive a drug cartridge, a hollow injection needle comprising a proximal end, configured to pierce a septum of the cartridge so as to establish a fluid communication between the cartridge and the needle, a cap arrangeable over the cartridge holder in a manner to cover the needle. In an initial state the cartridge is arranged within the cartridge holder with the septum axially spaced from the proximal tip of the needle, wherein the cap is adapted to move the needle relative to the septum for piercing it on movement of the cap relative to the cartridge holder, wherein one or more side openings are located in the cartridge holder, wherein the cap comprises one or more inner longitudinal ribs configured to protrude through the side openings for gripping by friction and fixing the drug cartridge in an axial position inside the cartridge holder.EFFECT : injection device is disclosed.14 cl, 7 dwg