Pen-type injector

A pen comprising

• a carpule having a longitudinal axis, a first end with a dispensing opening that can be closed by means of a closure part, a second end receiving at least one stopper in a direction of the longitudinal axis, and an interior tightly closed by the closure part and the at least one stopper;
• and
• a housing having a central axis, receiving the carpule, and having a piston rod and a drive, the piston rod interacting with the at least one stopper and arranged within the housing in a fixed position in a direction of the central axis of the housing, the drive for moving the at least one stopper within the interior of the carpule, the second end of the carpule inserted into the housing, the drive having a drive element that interacts with the carpule, the drive element operative to move the carpule into the housing in a direction of its longitudinal axis, which is arranged coaxially to the central axis of the housing, when the drive is activated, and upon activation of the drive, 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 a direction of the first end of the carpule.