Screw spindle pump

A screw spindle pump, comprising a spindle housing, in which a drive spindle and at least one running spindle meshing therewith are received in spindle bores, wherein the drive spindle has a cylindrical spindle core and at least two spindle profiles around the circumference of the spindle core, and, on an end face of the drive spindle, in a depression which is axially delimited by a planar bottom surface and in which the two profile valleys open out between the two spindle profiles in a manner offset by 180°, there is arranged a disk-shaped coupling element, which has an insertion receptacle for a drive shaft of a drive motor and which is coupled to the drive spindle for conjoint rotation therewith in at least one direction of rotation of the drive spindle via a form-fitting engagement with axially protruding projections that laterally delimit the depression and engage in lateral receptacles of the coupling element, wherein the bottom surface is delimited by the spindle core in the region of the openings of the two profile valleys, and the coupling element has a rounded configuration, corresponding to the shape of the spindle core, in the element regions that adjoin the regions of the opening, wherein the diameter of the coupling element, in the region of the rounded element regions, corresponds at most to the diameter of the spindle core or is smaller than the diameter of the spindle core.