A cartridge holder is presented having a first cartridge retainer, at least a second cartridge retainer and a locking device for each cartridge retainer, wherein each cartridge retainer is configured to receive a medicament reservoir and wherein each cartridge retainer is movable between a closed and an open position, wherein the locking devices are configured to lock and unlock the cartridge retainers in the closed position and wherein the locking devices are configured to operate such that only one of the cartridge retainers at a time is movable into the open position. An apparatus is also presented that has a main body and a cartridge holder, wherein the cartridge holder is removably attached to the main body. A method for inserting of a medicament reservoir in a cartridge holder or in an apparatus is also described.
