A pen comprising - a carpule that has a longitudinal axis, • a first end with a dispensing opening that can be closed by means of a closure part, • a second end via which at least one stopper can be inserted, the stopper being moveable in the direction of the longitudinal axis, and • an interior that is tightly closed by the closure part and the at least one stopper, - a housing that has a central axis, receives the carpule, and • has a piston rod that interacts with the at least one stopper, and • has a drive for moving the at least one stopper within the interior of the carpule, wherein • the carpule can be inserted into the housing with the second end leading, characterized in that - the piston rod is arranged within the housing in a fixed position when seen in the direction of the central axis of the housing, - the drive has a drive element that interacts with the carpule, - the drive element moves the carpule into the housing in the direction of its longitudinal axis, which is arranged coaxially to the central axis of the housing, when the drive is activated, and in the process the piston rod is held in a fixed position with respect to the longitudinal direction of the housing such that - the piston rod, which is engaged in the second end of the carpule, moves the at least one stopper within the interior of the carpule in the direction of the first end of the carpule. - a carpule that has a longitudinal axis, • a first end with a dispensing opening that can be closed by means of a closure part, • a second end via which at least one stopper can be inserted, the stopper being moveable in the direction of the longitudinal axis, and • an interior that is tightly closed by the closure part and the at least one stopper, • a first end with a dispensing opening that can be closed by means of a closure part, • a second end via which at least one stopper can be inserted, the stopper being moveable in the direction of the longitudinal axis, and • an interior that is tightly closed by the closure part and the at least one stopper, - a housing that has a central axis, receives the carpule, and • has a piston rod that interacts with the at least one stopper, and • has a drive for moving the at least one stopper within the interior of the carpule, wherein • the carpule can be inserted into the housing with the second end leading, • has a piston rod that interacts with the at least one stopper, and • has a drive for moving the at least one stopper within the interior of the carpule, wherein • the carpule can be inserted into the housing with the second end leading, - the piston rod is arranged within the housing in a fixed position when seen in the direction of the central axis of the housing, - the drive has a drive element that interacts with the carpule, - the drive element moves the carpule into the housing in the direction of its longitudinal axis, which is arranged coaxially to the central axis of the housing, when the drive is activated, and in the process the piston rod is held in a fixed position with respect to the longitudinal direction of the housing such that - the piston rod, which is engaged in the second end of the carpule, moves the at least one stopper within the interior of the carpule in the direction of the first end of the carpule.