Plasma prolactin in schizophrenia subjects treated with Seroquel (ICI 204,636)

Treatment with standard antipsychotic medications causes side effects such as hyperprolactinemia and extrapyramidal symptoms. Because these side effects can cause noncompliance with antipsychotic medication and consequent relapse, they add to the morbidity of schizophrenia. A compound with antipsychotic efficacy but without the side effects of standard antipsychotic agents would improve compliance and treatment outcomes and enhance quality of life. Improved compliance, reduced relapse, and decreased hospitalization would also reduce the cost of treatment of schizophrenia. Seroquel (ICI 204,636), an atypical antipsychotic compound in Phase III development, was found to be well tolerated and effective in treating subjects with DSM-III-R schizophrenia in three Phase II clinical trials. Analysis of plasma prolactin concentrations obtained during these trials revealed that ICI 204,636 did not differ from placebo in its effect on plasma prolactin after up to 6 weeks of treatment; no significant difference was found in the degree of decline of plasma prolactin levels when subjects treated with ICI 204,636 and placebo were compared. A significant difference was found, however, between ICI 204,636- and chlorpromazine-treated subjects; prolactin levels in ICI 204,636-treated subjects fell to a greater degree than they did in chlorpromazine-treated subjects, however in all three trials, ICI 204,636 did not cause sustained elevation of prolactin.