Inhalation device system for the inhalative administration of a medically active liquid in nebulized form, the system comprising an inhalation device and an exchangeable reservoir for holding the medically active liquid, wherein the inhalation device comprises - a housing having a receiving unit , the receiving unit having a connection unit adapted to releasably and fluidically connect to a connection port of the exchangeable reservoir , the receiving unit being adapted to receive and fluidically connect to the exchangeable reservoir ; - a nozzle for nebulization of the medically active liquid; and - a pumping unit arranged within the housing and adapted to be fluidically connected to the reservoir and to the nozzle and being adapted to convey the medically active liquid in a downstream direction from the reservoir to the nozzle ; wherein - the exchangeable reservoir is provided in form of a cartridge system having an overall volume (V o ) and comprising a container portion having an effective volume (V e ) for holding the medically active liquid and a connection port adapted to releasably and fluidically connect the cartridge system to the pumping unit , wherein the cartridge system further comprises an extension element having an additional volume (V a ), the extension element being attached to the outer surface of the container portion ; characterized in that the extension element of the cartridge system is removably attached to the outer surface of the container portion ; optionally wherein the force necessary to remove the extension element from the outer surface of the container portion is higher than the force needed to remove the cartridge system from the receiving unit of the inhalation device . - a housing having a receiving unit , the receiving unit having a connection unit adapted to releasably and fluidically connect to a connection port of the exchangeable reservoir , the receiving unit being adapted to receive and fluidically connect to the exchangeable reservoir ; - a nozzle for nebulization of the medically active liquid; and - a pumping unit arranged within the housing and adapted to be fluidically connected to the reservoir and to the nozzle and being adapted to convey the medically active liquid in a downstream direction from the reservoir to the nozzle ; wherein - the exchangeable reservoir is provided in form of a cartridge system having an overall volume (V o ) and comprising a container portion having an effective volume (V e ) for holding the medically active liquid and a connection port adapted to releasably and fluidically connect the cartridge system to the pumping unit , wherein the cartridge system further comprises an extension element having an additional volume (V a ), the extension element being attached to the outer surface of the container portion ; characterized in that the extension element of the cartridge system is removably attached to the outer surface of the container portion ; optionally wherein the force necessary to remove the extension element from the outer surface of the container portion is higher than the force needed to remove the cartridge system from the receiving unit of the inhalation device . <EOS>