Quantitative determination of olanzapine in rat brain tissue by high-performance liquid chromatography with electrochemical detection

A sensitive assay was developed for the measurement of olanzapine in rat brain tissue using HPLC with electrochemical detection. The assay has a lower limit of quantitation of 0.5 ng/ml in tissue homogenate and utilizes a liquid-liquid extraction followed by reversed-phase HPLC for the quantitative analysis of olanzapine. The method provided a linear response for olanzapine over a concentration range of 0.5-100 ng/ml with a coefficient of determination (r(2)) greater than 0.9995. The extraction efficiencies of olanzapine and internal standard (LY170158) were greater than 82% in brain tissue. The intra-assay and inter-assay relative errors ranged from -5.38 to 17.60% and -3.25 to 10.53%, respectively. The intra-assay and inter-assay RSD values were in the range of 1.12 to 6.96% and 3.78 to 6.68%. Long-term stability studies showed that brain tissue homogenate samples spiked with olanzapine and internal standard are stable at -70 degreesC for at least 110 days. However, a room temperature stability study showed that olanzapine was not stable in brain homogenate if the sample was exposed at 25 degreesC longer than 2 h. This method has been used for the study of the disposition and pharmacokinetics of olanzapine in male Sprague-Dawley rats. (C) 2001 Elsevier Science B.V. All rights reserved.