Benzodiazepines are organic chemical substances, made of two carbon rings. Certain benzodiazepines can be used as drugs that increase the effect of the neurotransmitter GABA. The resulting drug has sedative effects. Depending on the drug, the effect may be stronger or weaker. The first benzodiazepine, chlordiazepoxide (Librium), was discovered accidentally by Leo Sternbach in 1955, and made available in 1960 by the medicine company Hoffmann–La Roche.