Which of the following antipsychotics is a partial agonist at the dopamine D2 receptor?

Brexpiprazole is classified as a partial agonist at the dopamine D2 receptor, which distinguishes it from other antipsychotics that primarily function as full antagonists or have different mechanisms of action. This means that brexpiprazole can modulate dopamine activity in a unique way; it has the ability to activate D2 receptors but to a lesser extent than dopamine itself. This characteristic allows brexpiprazole to help alleviate symptoms of psychosis while potentially minimizing some of the side effects that are common with full D2 receptor antagonists.

In contrast, clozapine primarily acts as a D2 antagonist but is also notable for its effects on serotonin receptors, making it effective for treatment-resistant schizophrenia. Haloperidol and risperidone are both considered typical or atypical antipsychotics, respectively, and function primarily as antagonists at D2 receptors. Their main therapeutic action involves blocking these receptors, which can lead to more pronounced side effects related to dopamine blockade. Brexpiprazole’s partial agonism offers a different approach, which may result in a more favorable side effect profile for certain patients.