γ-Hydroxybutyric acid (GHB), also known as 4-hydroxybutanoic acid and sodium oxybate (INN), is a naturally occurring substance found in the human central nervous system, as well as in wine, beef, small citrus fruits, and almost all animals in small amounts. It is also categorized as an illegal drug in many countries. It is currently regulated in Australia and New Zealand, Canada, most of Europe and in the US. GHB as the sodium salt, known as sodium oxybate, is sold by Jazz Pharmaceuticals under the name Xyrem to treat cataplexy and excessive daytime sleepiness in patients with narcolepsy.