Randomised double-blind comparison of the incidence of tardive dyskinesia in patients with schizophrenia during long-term treatment with olanzapine or haloperidol

BackgroundTardive dyskinesia is important in the side-effect profile of antipsychotic medication.AimsThe development of tardive dyskinesia was evaluated in patients treated with double-blind, randomly assigned olanzapine or haloperidol for up to 2.6 years.MethodsTardive dyskinesia was assessed by the Abnormal Involuntary Movement Scale (AIMS) and Research Diagnostic Criteria for Tardive Dyskinesia (RD-TD); it was defined as meeting RD-TD criteria at two consecutive assessments. The risk of tardive dyskinesia, the relative risk, incidence rate, and incidence rate ratio were estimated.ResultsThe relative risk of tardive dyskinesia for the overall follow-up period for haloperidol (n=522) v. olanzapine (n=1192) was 2.66 (95% CI=1.50–4.70). Based on data following the initial six weeks of observation (during which patients underwent medication change and AIMS assessments as frequently as every three days), the one-year risk was 0.52% with olanzapine (n=513) and 7.45% with haloperidol (n=114). The relative risk throughout this follow-up period was 11.37 (95% Cl=2.21–58.60).ConclusionOur results indicated a significantly lower risk of tardive dyskinesia with olanzapine than with haloperidol.