Ativan (lorazepam) belongs to a group of drugs called benzodiazepines. Lorazepam affects chemicals in the brain that may be unbalanced in people with anxiety. Ativan is used to treat anxiety disorders. Ativan may also be used for purposes not listed in this medication guide. You should not use Ativan if you have narrow-angle glaucoma or myasthenia gravis, or if you are allergic to Valium or a similar medicine. Do not use lorazepam if you are pregnant.