A neuromuscular stimulator device is described having a plastic casing housing control electronics which are maintained in contact with a power source by a metal retaining clip. The casing includes an integral cover which may be opened by breaking lines of weakness formed in the cover. The cover and clip are of such relative sizes and shapes so that once the cover is open, the clip may only be removed from the casing by deforming the clip. This deformation will ensure that the clip and other components cannot be replaced back in the casing, such that the device cannot easily be reused. In addition, the cover is not replaceable, due to the broken portions of the casing.