Neuroleptic radioreceptor activity and clinical outcome in schizophrenia

The relationship between serum haloperidol concentration and clinical response was examined in 27 schizophrenic inpatients between the ages of 18 and 56 years. All patients were treated with haloperidol, 20 mg/day for the first 2 weeks. Dosage adjustment after 2 weeks of treatment was made in seven subjects based on poor clinical response or side effects. Haloperidol activity was determined by the radioreceptor assay for neuroleptics on weeks 2 and 4 serum samples. The results indicated that higher radioreceptor activity levels, particularly above 22 ng/ml, were associated with poorer clinical response. The data suggest that radioreceptor activity levels are not at a steady state after 2 weeks drug treatment. Additionally, problems secondary to low sensitivity of the radioreceptor assay may limit its utility at low serum concentrations.