HL-Histamine receptor affinity predicts short-term weight gain for typical and atypical antipsychotic drugs

As a result of superior efficacy and overall tolerability, atypical antipsychotic drugs have become the treatment of choice for schizophrenia and related disorders, despite their side effects. Weight gain is a common and potentially serious complication of some antipsychotic drug therapy, and may be accompanied by hyperlipidemia, hypertension and hyperglycemia and, in some extreme cases, diabetic ketoacidosis. The molecular mechanism(s) responsible for antipsychotic drug-induced weight gain are unknown, but have been hypothesized to be because of interactions of antipsychotic drugs with several neurotransmitter receptors, including 5-HT2A and 5-HT2Cserotonin receptors, H1-histamine receptors, α1- and α2-adrenergic receptors, and m3-muscarinic receptors. To determine the receptor(s) likely to be responsible for antipsychotic-drug-induced weight gain, we screened 17 typical and atypical antipsychotic drugs for binding to 12 neurotransmitter receptors. H1-histamine receptor affinities for this group of typical and atypical antipsychotic drugs were significantly correlated with weight gain (Spearman ρ=−0.72; p less than 0.01), as were affinities for α1A adrenergic (ρ=−0.54; p less than 0.05), 5-HT2C (ρ=−0.49; p less than 0.05) and 5-HT6 receptors (ρ=−0.54; p less than 0.05), whereas eight other receptors' affinities were not. A principal components analysis showed that affinities at the H1, α2A, α2B, 5-HT2A, 5-HT2C, and 5-HT6 receptors were most highly correlated with the first principal component, and affinities for the D2, 5-HT1A, and 5-HT7 receptors were most highly correlated with the second principal component. A discriminant functions analysis showed that affinities for the H1 and α1A receptors were most highly correlated with the discriminant function axis. The discriminant function analysis, as well as the affinity for the H1-histamine receptor alone, correctly classified 15 of the 17 drugs into two groups; those that induce weight gain and those that do not. Because centrally acting H1-histamine receptor antagonists are known to induce weight gain with chronic use, and because H1-histamine receptor affinities are positively correlated with weight gain among typical and atypical antipsychotic drugs, it is recommended that the next generation of atypical antipsychotic drugs be screened to avoid H1-histamine receptors