Panamesine (; developmental code name EMD-57455) is a sigma receptor antagonist that was under development by Merck as a potential antipsychotic for the treatment of schizophrenia in the 1990s but was never marketed. It is a selective antagonist of both sigma receptor subtypes, the ÃÂ<sub>1</sub> and ÃÂ<sub>2</sub> receptors (IC<sub>50</sub> = 6 nM). In addition, the major metabolite of the drug, EMD-59983, has high affinity for the sigma receptors (IC<sub>50</sub> = 24 nM) and the dopamine D<sub>2</sub> (IC<sub>50</sub> = 23 nM) and D<sub>3</sub> receptors, with potent antidopaminergic activity. Panamesine reached phase II clinical trials for schizophrenia prior to the discontinuation of its development.
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