 They are the dibenzazepines (imipramine, desipramine, clomipramine, trimipramine, lofepramine) and the dibenzocycloheptadienes (amitriptyline, nortriptyline, protriptyline, butriptyline).Minor TCA 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, TCAs can also be usefully grouped based on the number of substitutions of the side chain amine.