- A type of drug used to relieve anxiety and insomnia (trouble sleeping). Benzodiazepines are also used to relax muscles and prevent seizures. They increase the effect of a chemical in the brain called GABA, which is a neurotransmitter (a substance that nerves use to send messages to one another). This causes brain activity to slow down. Benzodiazepines are a type of CNS depressant.