Sleeping pill molecule. Computer model of a molecule of the sleeping pill drug triazolam. Atoms are represented as spheres and are colour- coded: carbon (purple), hydrogen (white), nitrogen (pink) and chlorine (green). Triazolam belongs to a group of drugs, known as benzodiazepines, that 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. Triazolam was banned in the UK in 1991 due to a high frequency of psychiatric side effects, which include hallucinations, paranoia and aggression.