Antagonism of central histamine H1 receptors by antipsychotic drugs.

The activity of 8 widely antipsychotic drugs as antagonists of central histamine H1 receptors was determined from the inhibition of the binding of 3H-mepyramine to a membrane fraction from guinea-pig brain. The phenothiazines examined, clorpromazine, fluphenazine, thioridazine and trifluoperazine, were all potent H1 antagonists. Both alpha- and beta-flupenthixol were potent inhibitors, but butaclamol, although less potent, showed stereospecificity. Haloperidol and spiperone were markedly weaker antihistamines than the phenothiazines.