Clozapine enhances neurocognition and clinical symptomatology more than standard neuroleptics

Neurocognition and clinical symptomatology were evaluated in 27 patients with schizophrenia during a double-blind, placebo-controlled, crossover study involving clozapine, an atypical antipsychotic agent, and haloperidol, a conventional neuroleptic. Patients were assessed 5 to 6 weeks after initiation of each phase. Clinical symptomatology, based on Brief Psychiatric Rating Scale and Scale for the Assessment of Negative Symptoms ratings, markedly improved after treatment with both haloperidol and clozapine. The beneficial effects of clozapine were statistically significantly greater than the effects from the haloperidol treatment. Regarding neurocognition, both agents proved efficacious in improving performance on nearly all measures compared with placebo. In addition, as compared with haloperidol, clozapine significantly improved performance on Trails B, Verbal Fluency, and measures of delayed verbal memory, and it tended to increase performance on most measures. Additional analyses indicated that the improvement on neurocognitive measures was not because of symptom amelioration; rather, neurocognitive deficits seem to be an intrinsic enduring feature of schizophrenia. The superiority of clozapine over haloperidol may be related to clozapine's unique psychopharmacologic profile.