Sleeping pill molecule. Computer model of a molecule of the sleeping pill drug temazepam. Atoms are represented as spheres and are colour- coded: carbon (light blue), hydrogen (white), nitrogen (dark blue), oxygen (red) and chlorine (green). Temazepam belongs to a group of drugs known as benzodiazepines, which are used to treat insomnia. It promotes sleep by enhancing the effects of the neurotransmitter gamma-aminobutyric acid (GABA), which inhibits nerves and brain activity. The drug has a short half-life and so does not cause drowsiness the next morning.