ABSTRACT
OBJECTIVES: This multicenter clinical trial involving 13 hospital sites compared the safety of switching to olanzapine between 'direct switching method' and 'start-tapering switching method'. METHOD: This study included both inpatients and outpatients who fulfilled the criteria for schizophrenia as defined in the ICD-10, and were in need to be appropriate for switching antipsychotics. Subjects were randomly assigned to one of the two switching methods. For 'direct switching method' group, previous antipsychotics were abruptly discontinued and 10mg of olanzapine was administered, whereas for 'start-tapering switching method' group, initially 10mg of olanzapine was administered and previous antipsychotics was gradually tapered for 2 weeks. Olanzapine was used for 6 weeks and the dose was adjusted within the range of 5-20mg. The safety of switching to olanzapine was measured with vital signs including body weight, adverse events reported spontaneously, laboratory tests, and various scales such as Simpson-Angus Scale(SAS), Barnes Akathisia Rating Scale(BARS), Abnormal Involuntary Movement Scale(AIMS), and Liverpool University Neuroleptic Side Effect Rating Scale(LUNSERS). RESULTS: 103 patients were switched to olanzapine in this study. The comparison between two switching methods did not show any significant difference in the dosage of olanzapine used, the concomitant use of benzodiazepine, the rate and reasons of drop-out, the adverse events, vital signs, laboratory tests, and most scales for measuring side-effects. However, the decrease in AIMS scores was significantly lower in 'direct switching method' group, and the concomitant use of anticholinergics was comparatively greater in 'start-tapering switching method' group. At baseline, SAS and BARS scores were 3.5 and 1.8 points respectively, and more than 70% of the subjects showed hyperprolactinemia. After switching to olanzapine, SAS, BARS, and AIMS scores were significantly decreased and the proportion of the patients with hyperprolactinemia was also decreased to less than 30%. However significant weight gain after the treatment of olanzapine was observed regardless of switching method. CONCLUSION: This study may suggest that switching to olanzapine can be done with relatively high safety regardless of switching methods and olanzapine can significantly decrease some side-effects induced by other antipsychotics.