Benzodiazepines were discovered by accident in the 1950s in Switzerland by researchers at HoffmanLaRoche. They were first marketed in 1960 with the introduction of Librium. Benzodiazepines have a number of clinical effects: anxiolysis, sedation, amnesia, muscle relaxation and eventually anaesthesia. They produce this action by two main routes.
• First, and principally, benzodiazepines act in the central nervous system (CNS) via the gamma-amino butyric acid (GABA) network. GABA is an inhibitory neurotransmitter found in the brain and spinal cord. Benzodiazepines act by attaching to specific receptors close to the GABA receptors, prolonging the time the GABA is attached and producing a sedative effect.
• Second, benzodiazepines can attach directly to receptors for glycine (another inhibitory neurotransmitter) in the brainstem and spinal cord, producing anxiolysis and relaxation.
All benzodiazepines produce respiratory depression to some degree by a combination of CNS depression and thoracic muscle relaxation. They also produce mild hypotension as a result of muscle relaxation decreasing vascular resistance. As a result, the heart rate often rises as the body compensates for the reduction in blood pressure.
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