A benzodiazepine (sometimes colloquially "benzo"; often abbreviated "BZD") is a psychoactive drug whose core chemical structure is the fusion of a benzene ring and a diazepine ring. The first such drug, chlordiazepoxide (Librium), was discovered accidentally by Leo Sternbach in 1955, and made available in 1960 by Hoffmann–La Roche, which has also marketed the benzodiazepine diazepam (Valium) since 1963. - Source: Wikipedia
