Determination Of Teicoplanin In Human Plasma And Its Application To Population Pharmacokinetics Study

Gram-positive bacteria is one of the most common pathogens in intensive care units（ICU）.Currently,the use of glycopeptide antibiotic for this infection is preferred in the clinic.Teicoplanin,as a novel glycopeptide antibiotic which is widely used in clinical,exhibits strong antibacterial activity against Gram positive bacterial and MRSA but fewer adverse effects.Teicoplanin is highly bound to serum albumin and has a long elimination half-life.Sufficient loading dose and maintenance dose have been recommended to quickly achieve the target concentration and excellent outcomes and reduce incidence of drug resistance.Critically ill patients which influenced by disease state or medical interventions like continuous renal replacement therapies（CRRT）are always in a particular pathophysiological situation.These factors have led to pharmacokinetic changes.It has been reported that the standard dosing regimen（400mg q12h×3,400mg qd）is insufficient to achieve 10mg/ml in more than 70%of 50 patients.Therefore,our study aimed to establish a population pharmacokinetic model of teicoplanin and to explore the individualised dosage regimens in critically ill patients.Objective:To establish a high-performance liquid chromatography-mass spectrometry（HPLC-MS）method for the quantitative determination of teicoplanin in human plasma.To evaluate the Clinical effect and safety of different doses of teicoplanin on treatment of pulmonary infection with gram-positive bacteria in critically ill patients.To establish a population pharmacokinetics model of teicoplanin in critically ill patients and use simulation to optimize dosing regimen.Methods:Plasma of 50μL was prepared by protein precipitation with acetonitrile,used daltomycin as internal standard（IS）.Chromatographic separation was performed on a Welch Ultimate XB C₁₈ column（2.1×50 mm,3μm）;column temperature:40℃;mobile phase:acetonitrile-water（0.5%formic acid）,gradient elution within 5.5 min.The concentration of teicoplanin in plasma was determined by ESI ion source and positive ion mode multi-reaction monitoring method（MRM）.The ion transitions were performed at m/z 940.5→316.2 for teicoplanin and m/z 811.0→313.0 for daltomycin,with the collision voltage of 20 e V and 42 e V,respectively.The specificity,carryover,matrix effect,linearity,accuracy and precision of the method,and the stability of plasma samples were investigated. A total of 106 patients with pulmonary infection caused by gram-positive bacteria who were treated with teicoplanin in the intensive care unit of Guangdong Provincial People’s Hospital from Jan 2018 to Dec 2020 were retrospectively analyzed.A total of 60 patients received standard-dose group,46 in the high-dose group.The gender,age,weight,APACHEⅡ,serum creatinine（SCr）,serum albumin,and main diagnosis of admission,underlying diseases,bacteriology were collected for logistic regression analysis to find the possible factors influencing the clinical efficacy of pulmonary infection with gram-positive bacteria in critically ill patients.The clinical efficacy,bacterial clearance rate and safety were evaluated as well.A total of 347 blood samples were prospectively collected from 151 critically ill patients receiving teicoplanin intravenously using sparse sampling.The drug concentration in plasma were detected by HPLC-MS method established and collected clinically relevant information.A two-compartment model was used to perform the PK analysis and established a population PK model of teicoplanin in critically ill patients.The stability and prediction of the final model were evaluated by internal and external evaluation.Monte Carlo simulation was used to optimize dosing regimen of teicoplanin.Results:The linear relationship of plasma teicoplanin was good in the range of 1.0 to 100 mg/L,and the lower limit of quantification was 1.0 mg/L.The standard deviation（RSD）of intra-batch and inter-batch precision was≤10.9%,and the normalized matrix effect of teicoplanin was92.7%-109.3%and the RSD was≤12.0%.Plasma samples may be stored at-20℃for at least41 days.No interference was found in clinical samples with good method stability.The clinical efficacy and microbiological eradication in the patients with pulmonary infection caused by gram-positive bacteria higher in the high-dose teicoplanin group than the standard-dose group（73.9%vs.51.7%,58.7%vs.38.3%,P<0.05）.The duration of treatment shorter in the high-dose teicoplanin group than the standard-dose group（8 vs.11,P<0.05）.The incidence of adverse reactions was no significant difference between the two groups（6.52%vs.6.67%,P>0.05）.Binary Logistic regression analysis indicated that high-dose teicoplanin was independent protective factor[odds ratio（OR）2.672,95%confidence internal（95%CI）:1.110-6.434,P=0.028]and APACHEⅡscore was the independent risk factor（OR 0.925, 95%CI:0.863-0.991,P=0.026）for the clinical efficacy in the patients with pulmonary infection caused by gram-positive bacteria.In the final model,the e GFR estimated by the CKD-EPI equation was the only significant covariate of teicoplanin clearance（e GFR-CL 0.0082）.Estimated population PK parameters including clearance（CL）,central volume of distribution（V₁）,intercompartmental clearance（Q）and volume of distribution of the peripheral compartment（V₂）were 0.838 L/h,14.4 L,3.08 L/h and 51.6 L.The between-subject variability were 37.7%,26.6%,0 and 62.2%.The residual variability was 0.317.The final model formula is:CL（L/h）=0.838×（1+（e GFR-50）×0.0082）×e^0.142V1（L）=14.4×e^0.071 Q（L/h）=3.08 V2（L）=51.6×e^0.387 The established final model is stable and predictable verified by GOF,bootstrap,NPDE and prediction error.Only for the critically ill patients with severe renal impairment（e GFR≤30m L/min）using standard dose of teicoplanin（400 mg q12h×5,400 mg qd）can achieve effective treatment of trough concentration at 72 h and 168 h after the initial loading dose.We simulated higher dosing regimen for each group stratified by the type of infection and renal function and calculated the probability of target attainment（PTA）.Simplified loading dose and maintenance dose regimens for each group of critically ill patients were created to achieve the individualization of teicoplanin therapy.Conclusion:The method is simple,sensitive,accurate and reliable,and is suitable for the determination of teicoplanin in human plasma.The high-dose of teicoplanin has a definitive clinical efficacy on treatment of pulmonary infection with gram-positive bacteria in critically ill patients,which can significantly improve the total bacterial clearance rate,and reduce the duration of treatment,without increasing the incidence of adverse drug reactions.This study established a population pharmacokinetics model of teicoplanin in critically ill patients.The PK model was verified stable,effective and predictable and has a important value for the individualization of teicoplanin therapy in critically ill patients.