Ativan is a brand name for the medication lorazepam, which belongs to a class of drugs known as benzodiazepines. Benzodiazepines are central nervous system depressants that work by enhancing the effects of a neurotransmitter called gamma-aminobutyric acid (GABA) in the brain. GABA helps to calm excessive electrical activity, leading to a sedative and anxiolytic (anxiety-reducing) effect.