Sleeping pills. Pills of Stilnoct, on a box. These are prescribed to treat insomnia, an inability to fall asleep, or sleep long enough. It has many possible causes, including environmental factors such as noise and light, too much caffeine, lack of exercise, anxiety, depression and various psychiatric illnesses. Sleeping drugs, such as in this case zolpidem and imidazopyridine, promote sleep by reducing the activity of nerve cells within the brain. Long-term use of sleeping pills can lead to tolerance and dependence.