Aripiprazole: examining the clinical implications of D2 affinity

Schizophrenia is a prevalent psychiatric illness, which causes significant financial and social burden on the population overall. The development of second generation antipsychotics, such as Aripiprazole, Risperidone, and Paliperidone, has changed treatment practice for many psychiatrists. Aripiprazole has extremely high binding affinity for the dopamine D2 receptor, which is the receptor thought to be responsible for the antipsychotic effect, although Aripiprazole is not the most potent of the second generation antipsychotics. In theory, Aripiprazole could displace or outcompete other, more potent antipsychotics, prompting decreased antipsychotic effect. We describe a proposed case of this phenomenon, Ms. A. We describe how Aripiprazole may have caused a worsening of psychiatric symptoms by blocking the antipsychotic effects of Paliperidone due to its strong binding affinity for the D2 receptor. Aripiprazole has a high affinity for the D2 receptor, but may have a lesser reduction of psychotic symptoms compared to other antipsychotics. Prescribers should be aware of this potential interaction and carefully consider initiating long-acting injectable forms of Aripiprazole to avoid this phenomenon.