&NA;Blonanserin (AD 5423) is a combined dopamine D2and serotonin 5-HT2receptor antagonist, currently undergoing phase III clinical trials in Japan with Dainippon Pharmaceutical as a potential antipsychotic agent. Blonanserin is unrelated structurally to typical antipsychotics or to newer agents such as risperidone. It is hoped that the combination of receptor blockade possessed by blonanserin will be effective against both the positive and negative symptoms of schizophrenia, with a low tendency to cause extrapyramidal symptoms.