Pharmacokinetic Study Of Olanzapine In Voluntary Oral Administration Rat Model

Background:Olanzapine, as one of the most commonly used atypical antipsychotic medications, has been associated with metabolic abnormalities, including weight gain, diabetes, insulin resistance, hyperlipidemia and so on. Those side effects reduce the patients’ tolerance to drugs and qualities of their lives. In the last decades, researches based on animal models revealed parts of the mechanisms of olanzapine. Injection and gavage are two primary administration routes for olanzapine rat models. However, injection and gavage would cause cumulative damage and stress to rats(especially in long-term olanzapine researches), which would affect the experiment results at molecular level. Besides, the main drug-delivery method of olanzapine in clinic is oral administration, and the differences of drug-delivery methods in rat models also possibly affect the pharmacokinetic(PK) parameters and molecular-level results in side effects mechanism experiments. Thus, voluntary oral administration model was designed as a better simulation of the clinical treating process of olanzapine to reduce the outside interrupt and stress to rats, thereby acquiring the real pharmacological mechanisms of olanzapine. The design and optimization of a rat model is based on the in vivo PK parameters of the drug in rats. But there is no existing research report for in vivo PK study of olanzapine voluntary oral administration rat model, therefore no data can clearly demonstrated the validity and superiority of that model. And with the lack of those data in olanzapine voluntary oral administration rat model, the optimization and application of this model would be affected. Besides, some researches based on those models got significantly different outcomes because of their methodology and dosage divergences. That meant olanzapine dosage and the number of administration per day should be put in primary concern to build a good animal model for time.In previous studies, the various dosage and administration frequency may be the mainly reason that caused greater fluctuation of in vivo olanzapine PK parameters in rats, yet no one has explored these effects. Above all, the unknowns will be affect the optimization and application of olanzapine voluntary oral administration rat model.Objective:Measured and obtained the in vivo PK parameters of olanzapine in olanzapine voluntary oral administration rat model.Optimizing olanzapine voluntary oral administration rat model, and demonstrating the validity and advantage of that model in clinical olanzapine in vivo situation simulation. So that it could be applied to olanzapine researches.Method:1、Built and tested a HPLC method that detecting olanzapine in rat tissues.2、Tested the concentration distribution and the concentration-time curves of olanzapine in rat plasma, liver and brain nuclei by the HPLC method in voluntary oral administration rat model.3、The in vivo PK parameters were calculated by DAS software.4、The m RNA changes of D2 and 5-HT2 C receptors in hippocampus and CPu of rat brain were tested by RT-q PCR.Results:1. HPLC method development and verification.The retention times of olanzapine and IS were 15.4 and 20.2 min. Calibration curves for olanzapine were linear over the concentration range of 5–640 ng/m L in plasma, 50-3200 ng/g in brain and 50-6400ng/g in brain, with a lower limit of quantification of 5 ng/m L. The intra- and inter-day precision values were less than 10.12 % and the accuracy was between 100±10 %. CV% of stability in those three tissues were less than 10 %. The results of this analysis method demonstrated that the method was good at detecting olanzapine in rat plasma, brain and liver, compliance with the requirements of biological sample measurement.2. PK study of olanzapine in voluntary oral administration rat model with single dose daily.There were similar patterns of olanzapine absorption and metabolism in rat plasma, liver and brain in voluntary oral administration rat model with single dose daily.Pharmacokinetic parameters of C max, T max and t1/2 in 6 mg/kg/day olanzapine voluntary oral administration rat model were 298.80 ng/m L, 0.69 h and3.35 h in plasma; 1285.50 ng/g, 0.75 h and 5.68 h in brain; 3055.85 ng/g, 0.75 h and 6.76 h in liver, respectively. Besides, T max in 1、3 mg/kg/day olanzapine voluntary oral administration rat model were also 0.75 h, and C max in those model were 134.88 ng/m L and 192.67 ng/m L, respectively.3. PK study of olanzapine in voluntary oral administration rat model with multi-dosage.When olanzapine was administered as three equal dose a day, C max, T max and t1/2were 141.04 ng/m L, 11.33 h and 3.46 h, respectively. And the MRT was extended. Olanzapine was able to sustain therapeutically in rat for 24 h so that the pharmacological function could last longer.4. Concentration and m RNA study of olanzapine in voluntary oral administration rat model.Rat brain nuclei were listed in olanzapine concentration decreasing order: Cg, hippocampus, CPu, cerebellum, Arc-VMH, Acb, brainstem and PFC. Olanzapine concentration in liver were 2145 ng/g. The m RNA changes of D2 and 5-HT2 C receptors in hippocampus and CPu in that model were significant decreased(P<0.05).Conclusion:According to the in vivo pharmacokinetic studies in olanzapine voluntary oral administration rat model with different dosages and dosing frequencies, this study successfully mimicked the clinic scenario of olanzapine treating, extended the pharmacological function period and demonstrated the validity and superiority of that model in clinical simulation. The optimal dosage of 3 mg/kg/day(t.i.d.) would increase the MRT of olanzapine, so that olanzapine could stay in therapeutically effective concentration for a longer time and prolong the pharmacological process of olanzapine. The concentration distribution of olanzapine and the m RNA changes of D2 and 5-HT2 C receptors in that model would play a support and guidance role in olanzapine mechanisms studies. Above all, olanzapine voluntary oral administration rat model can be used in pharmacological and side-effect researches of olanzapine and can provide a framework for potential therapeutics.