A spindle device for a piston, held in a reservoir containing a medicament fluid. The spindle device includes: a first displacement stage with a thread, a second displacement stage with a thread, a drive stage between the displacement stages and having two threads, with one thread engaging the thread of the first displacement stage forming a first spindle drive, and the second thread engaging the thread of the second displacement stage forming a second spindle drive. The first displacement stage and the drive stage move simultaneously in the direction of advance. The first and second displacement stages are connected in a rotationally fixed manner by an element axially surrounding the drive stage for the rotational securing, and the drive stage can be coupled in a rotationally fixed manner to an entrainment rod of a drive device, with the entrainment rod insertable into an axial hole on the drive stage.
