Olanzapine in Chinese patients with schizophrenia or bipolar disorder: a systematic literature review

Development of a population pharmacokinetic model of olanzapine for Chinese health volunteers and patients with schizophrenia

OBJECTIVE

Olanzapine is an atypical antipsychotic drug commonly used for the treatment of schizophrenia. However, there are still many complications associated with the use of olanzapine, and researchers continually strive to improve the handling of data from regular therapeutic drug monitoring (TDM). The objective of this study is to optimise the individualised treatment of olanzapine by establishing a population pharmacokinetics (PopPK) model in Chinese patients with schizophrenia.

METHODS

This study integrates an extensive collection of concentration data from healthy volunteers after a single dose and a less extensive collection of samples from patients undergoing TDM. A PopPK model was developed using non-linear mixed-effects modelling. Potential covariates, including the olanzapine manufacturer and patient gender and age, were assessed during model development. A total of 616 plasma concentration levels from 22 healthy male individuals in China and 458 concentration levels from 112 male and 122 female patients with schizophrenia undergoing TDM at 12 hospitals in China were included in the analysis. The concentration profile could be best described using a two-compartment model with first-order absorption and elimination.

RESULTS

The absorption rate (Ka) of olanzapine ranged from 2.85 h-1 to 5.39 h-1 for the different formulations. The typical absorption time delay was 0.877 hour. Body weight had a considerable effect on the apparent volume of the centre compartment and showed a power relationship.

CONCLUSIONS

A PopPK model of olanzapine in Chinese patients with schizophrenia was developed in this study. After determining the PK parameters of olanzapine, the results suggested that body weight exhibited a considerable impact effect on VC/F. The impact of subjects and formulations requires further study. The PopPK model established in this study is likely to provide some information for the individualised therapy of olanzapine.

TRIAL REGISTRATION NUMBER

ChiCTR-TRC-10000934; Results.

Efficacy and safety of olanzapine for treatment of patients with bipolar depression: Chinese subpopulation analysis of a double-blind, randomized, placebo-controlled study

BACKGROUND

Depression in bipolar I disorder responds to the atypical antipsychotic olanzapine. This subpopulation analysis assessed whether olanzapine is superior to placebo specifically in the treatment of Chinese patients with bipolar I depression.

METHODS

This was a subpopulation analysis of a 6-week, multicenter, double-blind, parallel, randomized, placebo-controlled trial among 12 Chinese study centers. Eligible inpatients and outpatients were randomized to olanzapine (5 to 20 mg/day) or placebo. Patients were primarily assessed by the Montgomery-Åsberg Depression Rating Scale total score. Secondary assessments used a range of other efficacy and safety measures. This subpopulation analysis was underpowered to show statistically significant differences between treatment groups.

RESULTS

In total, 210 patients (mean age 32.9 years at baseline, 54.3% females) were random-ized. Similar proportions of patients treated with olanzapine (75.0%) and placebo (72.9%) completed the double-blind phase. Baseline-to-endpoint least-squares mean ± standard error decrease in the Montgomery-Åsberg Depression Rating Scale total score in the olanzapine group (-13.55±0.80) was similar to that noted in the parent trial (-13.82±0.65). However, the difference between olanzapine and placebo groups was not statistically significant (P=0.44); this finding was also true for the secondary efficacy measures. A post hoc analysis showed a greater emergence of mania in the placebo group, which likely reduced the treatment difference between olanzapine and placebo in the primary efficacy measure. Safety data were consistent with the known safety profile of olanzapine, including a higher incidence of weight gain (≥7%) in the olanzapine group (24.1% vs 1.4%, P<0.001).

CONCLUSION

Olanzapine provides similar improvement in depression among Chinese and non-Chinese bipolar I patients. The lack of a statistically significant difference between the olanzapine and placebo groups in this Chinese subpopulation analysis may relate to an a priori lack of study power, and underestimation of the effect of olanzapine because of a greater emergence of mania in placebo-treated patients and missing data associated with a high early discontinuation rate.