Ambien also known as 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol (THIP ) is an experimental sleep aid drug developed by Lundbeck and Merck. In March, 2007, Merck and H. Lundbeck cancelled work on the drug, citing safety concerns and the failure of an efficacy trial. It acts on the GABA system, but possibly in a different way from benzodiazepines, nonbenzodiazepines and barbiturates – (Valium, Sodium Pentothal, Ambien etc.). Lundbeck states that ambien also increases deep sleep (stage 4). It is, however, not reinforcing like benzodiazepines are.