Amitriptyline, sold as a generic drug or under the brand name Elavil, is a tricyclic antidepressant drug (TCA) that works by increasing the amount of norepinephrine and serotonin available to the brain. These are two important neurotransmitters necessary for brain function. While the FDA approves amitriptyline for the treatment of depression, it has many off-label uses as well. These include treating anxiety, chronic pain, and insomnia, among others.