Brexpiprazole and cariprazine are classified as dopamine 'partial agonists' at D2 receptors. The therapeutic advantage of partial agonism over full antagonism (e.g., haloperidol) at D2 receptors includes:

• A Functional stabilization — acting as antagonist in hyperdopaminergic states and as agonist in hypodopaminergic areas, reducing both psychosis and negative symptoms/EPS ✓
• B Complete blockade of dopamine transmission preventing any breakthrough psychosis
• C Selective blockade of mesolimbic pathway only
• D Greater prolactin elevation due to stronger D2 blockade in tuberoinfundibular pathway

Explanation

Partial D2 agonists exhibit intrinsic activity intermediate between 0 and 100%. In dopamine-rich areas (mesolimbic — psychosis), they compete with dopamine and act as functional antagonists. In dopamine-deficient pathways (mesocortical — negative symptoms; nigrostriatal — motor control), they provide baseline dopaminergic tone, reducing EPS and improving cognition. This 'dopamine stabilizer' concept explains why partial agonists like aripiprazole, brexpiprazole, and cariprazine cause less EPS, hyperprolactinemia, and may improve negative symptoms compared to full D2 antagonists.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.