tricyclic antidepressant

Tricyclic antidepressants are chemical compounds used primarily as antidepressants. TCAs were first discovered in the early 1950s and marketed later in the decade. They are named after their chemical structure, which contains three rings of atoms. Tetracyclic antidepressants (TeCAs), which contain four rings of atoms, are a closely related group of antidepressant compounds.