There are two major groups of<unk> s in terms of chemical structure, which most, but not all,<unk> s fall into. The groupings are based on the<unk>  ring system. They are the dibenzazepines (imipramine, desipramine, clomipramine, trimipramine, lofepramine) and the dibenzocycloheptadienes (amitriptyline, nortriptyline, protriptyline, butriptyline). Minor<unk>  groups based on ring system include the dibenzoxepins (doxepin), the dibenzothiepines (dosulepin), and the dibenzoxazepines (amoxapine). In addition to classification based on the ring system,<unk> s can also be usefully grouped based on the number of substitutions of the side chain amine. These groups include the tertiary amines (imipramine, clomipramine, trimipramine, amitriptyline, butriptyline, doxepin, dosulepin) and the secondary amines (desipramine, nortriptyline, protriptyline). Lofepramine is technically a tertiary amine, but acts largely as a prodrug of desipramine, a secondary amine, and hence is more similar in profile to the secondary amines than to the tertiary amines. Amoxapine does not have the<unk>  side chain and hence is neither a tertiary nor secondary amine, although it is often grouped with the secondary amines due to sharing more in common with them. In 2021, a new method was developed at the Institute for Bioengineering of Catalonia for designing photochromic analogs of<unk>  drugs via (1) isosteric replacement of the two-atom bridge between the aromatic systems with an azo group and (2) opening of the central ring. The authors named the strategy "crypto-azologization".
Tricyclic antidepressant
Tetracyclic antidepressant
Atypical antidepressant
Heterocyclic antidepressant
Second-generation antidepressant
Antipsychotic
Atypical antipsychotic
Antipsychotic ester