This study proposes to conduct a clinical trial comparison of olanzapine and the combination
of a nicotinic cholinergic agonist, 3-[2,4-Dimethoxybenzylidene]anabaseine (DMXB-A) with a
dopamine D2 receptor antagonist, the mechanism common to all antipsychotic drugs, to test the
hypothesis that 7-nicotinic receptor agonism may be an additional necessary factor that
enhances the efficacy of olanzapine that allows its slight superiority to risperidone. This
trial would enroll patients taking olanzapine and record baseline measurements of clinical
symptoms, cognition, metabolic parameters, and extrapyramidal side effects. The subjects
would then be randomized to receive either risperidone or risperidone plus DMXB-A for 6 weeks
and then would again have measurements of clinical symptoms, cognition, metabolic parameters
and extrapyramidal side effects.