Binding of Antipsychotic Drugs to Human Brain Receptors Focus on Newer Generation Compounds

Using radioligand binding assays and post-mortem normal human brain tissue, we obtained equilibrium dissociation constants (K(d)s) for nine new antipsychotic drugs (iloperidone, melperone, olanzapine, ORG 5222, quetiapine, risperidone, sertindole, ziprasidone, and zotepine), one metabolite of a new drug (9-OH-risperidone), and three older antipsychotics (clozapine, haloperidol, and pimozide) at nine different receptors (alpha1-adrenergic, alpha2-adrenergic, dopamine D2, histamine H1, muscarinic, and serotonin 5-HT1A, 5-HT1D, 5-HT2A, and 5-HT2C receptors). Iloperidone was the most potent drug at the two adrenergic receptors. ORG 5222 was the most potent drug at dopamine D2 and 5-HT2c receptors, while ziprasidone was the most potent compound at three serotonergic receptors (5-HT1A, 5-HT1D, and 5-HT2A). At the remaining two receptors, olanzapine was the most potent drug at the histamine H1 receptor (Kd=0.087 nM); clozapine at the muscarinic receptor (Kd=9 nM). Certain therapeutic and adverse effects, as well as certain drug interactions can be predicted from a drug's potency for blocking a specific receptor. These data can provide guidelines for the clinician in the choice of antipsychotic drug.