Establishment Of A Liquid Chromatography-tandem Mass Spectrometry Method For The Determination Of Olanzapine And N-desmethylolanzapine In Plasma And Analysis Of The Plasma Concentration Influencing Factors

Background of the study:For olanzapine,it is the first-line drug for the treatment of schizophrenia,which has led to its clinical efficacy and adverse drug reactions being correlated with blood levels.In the European Association of Neuropsychopharmacology and Drug Psychiatry(ArbeitsgemeinschaftfurNeuropsychopharmakologie und PharmakopsychiatrieAGNP),therapeutic drug monitoring of olanzapine is strongly recommended as its latest guideline.However,the current use of olanzapine by clinicians in China is still empirically driven and lacks a scientific basis.Objectives:1 To establish a method for the determination of olanzapine and N-desmethyl olanzapine in human plasma by high performance liquid chromatography-tandem mass spectrometry(High performance liquid chromatography-tandem mass spectrometry,HPLC-MS/MS),which could be applied to olanzapine therapeutic drug monitoring in the clinical setting,and to preliminarily assess whether the AGNP recommended therapeutic reference concentration range for olanzapine is still applicable in the domestic population.2 Based on routine olanzapine therapeutic drug monitoring data from hospital clinics,the use of olanzapine as a therapeutic drug monitor was examined.Based on daily olanzapine therapeutic drug monitoring data,the factors influencing the plasma concentrations of olanzapine and its metabolite N-desmethyl olanzapine in olanzapine-treated patients with schizophrenia were examined and used to provide clinicians with reference data for rational drug use.Methods:1 Plasma samples were treated by protein precipitation with d8-olanzapine as internal standard and a methanol acetonitrile mixture was used,where a phenomenex Phenyl-Hexyl column(50 x 4.6mm,2.6 μm)was used.For gradient elution,the flow rate was 0.6 ml/min and the column temperature was 40℃,with an injection volume of 2 μL.An electrospray ionisation source,in positive ion mode,with multiple reaction monitoring mode scanning was used.The method is stable in terms of linearity,precision and accuracy,extraction recovery,matrix effect,specificity,and residual effect.Clinical olanzapine therapeutic drug monitoring data were also collected and compared to the AGNP recommended reference concentration range for olanzapine treatment.2Plasma concentration data for steady-state olanzapine and its metabolite N-desmethyl olanzapine were collected in 544 olanzapine-treated inpatients with schizophrenia,which allowed general patient information to be extracted from the medical record system.Age,gender,weight,combined medication and abnormal liver and renal function were counted,which influenced the plasma concentrations of olanzapine and its metabolite N-desmethyl olanzapine.Results:1 Olanzapine was well linear in the range of 3.2-160ng/ml with an accuracy of-8.56%-1.5%,precision less than 6%,extraction recovery 93.90%-97.79%and residual effect less than 10%;N-desmethyl olanzapine was well linear in the range of 1.6-80ng/ml with an accuracy of-6.88%-5.87%and Precision was less than 11%,extraction recoveries were 87.62%-93.39%and normalised matrix factors for both olanzapine and N-desmethyl olanzapine were in the range of 0.80-1.20.Method selectivity was good for olanzapine treatment as recommended by the AGNP,which can refer to the concentration range applicable to domestic patients.2 Multiple linear regression was used,which allowed analysis of the results suggesting that daily dose of olanzapine,patient gender,age,BMI,combined medication,and abnormalliver or kidney function explained approximately 45%of the variation in olanzapine plasma concentrations.Further comparative analysis revealed that olanzapine plasma concentrations were significantly higher in the older,female group than in the younger,male group;olanzapine dose-corrected plasma concentrations were significantly lower in the obese group than in the non-obese group;olanzapine plasma concentrations were significantly lower in the olanzapine combined with sodium valproate group than in the olanzapine alone group;no significant effect of abnormal kidney function on olanzapine plasma concentrations was found.Also,gender and body weight were studied,which were important factors influencing the plasma concentration of the olanzapine metabolite N-desmethyl olanzapine.Conclusion:In this study,a pre-treatment simplicity was established in which a short analytical time and high accuracy HPLC-MS/MS method for simultaneous detection of olanzapine and N-desmethyl olanzapine plasma concentrations was established.Psychiatric olanzapine therapeutic drug monitoring is a data analysis of olanzapine therapeutic drug monitoring,which can be prompted.The pharmacokinetics of olanzapine vary considerably between individuals,where the patient’s gender,age,BMI,and combined medications are all factors that influence olanzapine plasma concentrations.The combined effect of all factors needs to be considered when clinicians are treating with olanzapine,which allows for rational dosing regimens to be developed.