Medication continuation and compliance: A comparison of patients treated with clozapine and haloperidol

Background: This study compares medication continuation and regimen complia nce with the atypical antipsychotic medication clozapine versus the convent ional antipsychotic haloperidol. Method: Data from a 15-site double-blind, randomized clinical trial (N = 42 3) were used to compare patients with DSM-III-R schizophrenia assigned to c lozapine or haloperidol in terms of duration of participation while taking the randomly assigned study drug (continuation) and the proportion of presc ribed pills that were taken (compliance). Multiple regression analysis was used to determine the relationship of baseline characteristics and measures of clinical change to continuation for the entire sample and for patients assigned to each medication. Results: Patients assigned to clozapine continued taking the study drug for a mean of 35.5 weeks as compared with only 27.2 among patients assigned to haloperidol (F = 4.45, df = 1,422; p = .0001). No differences were found b etween the groups in the proportion of prescribed pills that were returned at any time-point. Among patients assigned to haloperidol, poorer continuat ion was associated with being older and greater continuation with receiving public support. Among patients on clozapine treatment, continuation was po orer among African American patients and greater among patients who showed reduced clinical symptoms and akathisia. Continuation with clozapine was gr eater even after adjusting for these factors. Conclusion: Continuation with medication is greater with clozapine than hal operidol and is partly explained by greater symptom improvement and reduced side effects. No differences were found in regimen compliance.