An administering apparatus for delivering a dosage of product including a casing with a reservoir for the product, a piston within the reservoir to deliver the product, a piston rod for engaging the piston, a drive device for driving the piston rod, and a dosage setting member mechanically engaging the piston rod and a stopper for the dosage setting member. The casing includes a front casing section containing a reservoir for the product and a rear casing section detachably connected to the front casing section. The front casing section is connected to or forms a first latching element, and the rear casing section is connected to or forms a second latching element. The latching elements are in latching engagement when the casing sections are connected. The casing sections may be axially fixed to one another by the latching engagement. The casing sections may alternately be fixed to one another, secured against rotating, with respect to a rotational movement about a longitudinal axis of the casing sections parallel to the advancing direction, by the latching engagement. The administering apparatus further includes a latching block coupled to the drive element such that the latching engagement can only be released in a releasing position of the drive element.