Amitriptyline is in a class of drugs called tricyclic antidepressants. Amitriptyline affects chemicals in the brain that may become unbalanced and cause depression. Amitriptyline is used to relieve symptoms of depression such as feelings of sadness, worthlessness, or guilt; loss of interest in daily activities; changes in appetite; tiredness; sleeping too much; insomnia; and thoughts of death or suicide.