Psychotropic drugs have also been organized according to structure (e.g., tricyclic), mechanism (e.g., monoamine, oxidase inhibitor [MAOI]), history (first generation, traditional), uniqueness (e.g., atypical), or indication (e.g., antidepressant). A further problem is that many drugs used to treat medical and neurological conditions are routinely used to treat psychiatric disorders.

- Benjamin James Sadock