GHB is used as a general anesthetic in Europe. In the US, the FDA approved GHB for use in the treatment of narcolepsy (a sleep disorder) in 2002. This approval came with severe restrictions, including its use only for the treatment of narcolepsy and the requirement of a patient registry monitored by the FDA.
GHB is known as a predatory drug: it can be slipped into a victim's drink, causing dizziness, confusion, drowsiness and sometimes loss of consciousness. When GHB is combined with alcohol, it is especially dangerous because the combination of two depressants can lead to overdose.
GHB acts on at least two sites in the brain: a GABA (gamma aminobutyric acid) receptor and a specific GHB binding site. Because GHB is a metabolite of the inhibitory transmitter GABA, it is found naturally in the brain but at concentrations much lower than doses that are abused.