Figure 3.

Classification and characteristics of atypical antipsychotic drugs. Figure shows chemical structures of atypical antipsychotics with their receptor binding profiles (affinities). Most atypical antipsychotics possess potent 5-HT₂ blocking actions and act as serotonin and dopamine antagonists (SDAs). Among SDAs, clozapine derivatives (e.g., olanzapine and quetiapine) show various actions on other receptors than D₂ and 5-HT₂ receptors, including histamine H₁, adrenergic α_1, and muscarinic blocking actions. Thereby, they are sometimes called as multi-acting receptor-targeted antipsychotics (MARTAs) and differentiated from SDAs (e.g., risperidone, perospirone, and lurasidone). Although aripiprazole possess moderate 5-HT₂ blocking activities, it primarily acts as a dopamine D₂ partial agonist. Furthermore, several atypical antipsychotics have own characteristics such as 5-HT_1A partial agonistic actions for perospirone, lurasidone and aripiprazole, 5-HT₆ blocking actions for olanzapine and quetiapine, and 5-HT₃ blocking actions for olanzapine.