General anesthetics are drugs that produce reversible loss of sensation and consciousness. They work by depressing the central nervous system. There are two main types - volatile liquids/gases that are inhaled, and non-volatile drugs given intravenously. Volatile agents include ether, chloroform, halothane and nitrous oxide. Non-volatile agents include thiopental sodium and ketamine. They produce anesthesia through actions on GABA receptors or NMDA receptors in the brain. Ideal anesthetics have properties like potency, ease of use, quick induction/recovery, lack of flammability, muscle relaxation, analgesia and low toxicity.