| Vancomycin is a tricyclic glycopeptide antibiotic. It is extensively recommended by evidence-based treatment guidelines and guidelines for treatment of MRSA infection as first-line therapeutic treatment for a variety of serious infections. Consensus of vancomycin treatment by Chinese expert also supports it as the first choice in clinical application for infections caused by methicillin-resistant Staphylococcus. Research has found that concentration of vancomycin was significantly correlated with clinical effect and adverse reaction and consentration kept between 10 and 20 ?g·m L-1 strongly indicated a great chance of successful treatment. On the other hand, the sensitivity of bacteria to vancomycin including minimum inhibitory concentration will also influence antibiotic efficacy. Clinical trials showed that AUC0-24h/MIC?400 was the vital PK/PD target of eradicating MRSAs. Considering its hydrophilic property, we have concluded that obesity, edema, application of haemodynamically active drugs, renal failure, sepsis and other factors that may cause the vancomycin apparent volume of distribution(Vd) and clearance rate varied, causing the change of pharmacokinetic parameters. We aimed to study the individual variability of vancomycin and provide prediction of pharmacokinetic parameters which will assist with dosage regimen adjustment.Firstly, we established an HPLC method and an LC-MS/MS method for the determination of vancomycin in human plasma and collected 95 samples used to compare with immunoassay meathod. HPLC method used norvancomycin as internal standard. 100?L of plasma sample containing vancomycin and internal standard extracted by the sedimentation with 10% perchloric acid were injected into HPLC. The chromatographic column of Agilent Eclipse XDB-C18 analytical column(250 mm×4.6 mm, 5 ?m) was used and the column temperature was 35?. The mobile phase was composed of KH2P04 buffer solutionmethanol(86:14, V/V)(p H=3.2) at a flow rate of 1 m L·min-1 with UV detection at 230 nm.LC-MS/MS method also used norvancomycin as internal standard. 100 ?L of plasma samples containing vancomycin were precipitated by acetonitrile containing internal standard and centrifuged. The supernatant was double diluted and then injected into LC-MS/MS. The separations were performed on an Agilent Eclipse XDB-C18 analytical column(100 mm × 2.1 mm, 3.5 ?m) with column temperature of 40?. Samples were eluted using a mobile phase composed of water(0.1% formic acid)- acetonitrile(90:10, V/V) at a flow rate of 0.2 m L·min-1.ESI was used which was performed in the multiple reaction monitoring mode(MRM) using target ions m/z 725.0 ? 44.0(vancomycin) and m/z 718.5?144.0(IS). Then we used the HPLC and LC-MS/MS method we established to determine 95 clinical samples and to compare with CLEIA meathod. It showed that there is a strong correlation between the two methods and the method of CLEIA(r=0.9621, P< 0.0001 and r=0.9466, P<0.0001) without obvious bias. The HPLC and LC-MS/MS method we established were rapid, sensitive, precise and reliable for the determination of vancomycin in human serum, which can be applied as alternative methods applying in the study of human vancomycin pharmacokinetics and practice of therapeutic drug monitoring.We further investigated the related factors of vancomycin pharmacokinetic parameters of patients diagnosed hematonosis. We collected the clinical data of 849 routine monitoring information from 244 patients and added data we searched to establish population pharmacokinetic model of vancomycin. The PPK model was established by nonlinear mixed-effect modeling(NONMEM). Pharmacokinetics of vancomycin was described separately as a one-compartment disposition model and a two-compartment disposition model. We have tried different factors including age, gender, body weight, creatinine clearance, types of disease and found that only creatinine clearance significantly reduced interindividual variations(P<0.01). For patients' data was all collected from clinical TDM, we planned to use the established one-compartment model for error diminution and to predict individual pharmacokinetic parameters of vancomycin and regimen adjustment. Based on the one-compartment PPK model, we also built a Monte Carlo simulation model by assuming a lognormal distribution of pharmacokinetic parameters and a discrete distribution of MIC with target of AUC0-24h/MIC?400. We set to run 1000 cases forsimulation to get probability of target attainment(PTA) of certain regimen and cumulative fraction of response(CFR). Model predicted when the MIC of MRSA equals 0.5 ?g·m L-1, the standard regimen can achieve satisfactory antibiotic activity, but when the MIC equals 1?g·m L-1, standard dose of 1g q12 h may be insufficient to make best clinical effect and predicts great failure risk. So we suggest a combination of TDM to help adjust regimen as well as considering patient's disease progression, ultimately administrating sufficient dosage to avoid failure of MRSA treatment and renal toxicity. Based on the simulation results, we suggested several dosage regimens to assist regimen adjustment differed by MIC value. Then we collected data of 25 patients who had separated pathogen to testify if the suggested regimen fits for clinical application. For patients who lacked concentration of vancomycin, we determined using the built HPLC and LC-MS-MS method. For all patients, we calculated CL by the built one-compartment model. Comparing parameters of two different clinical outcome groups, we found the failure group tended to have lower value of AUC0-24h/MIC?400. There was no significant correlation between Ctrough and AUC0-24h/MIC and only AUC0-24h/MIC correlated significantly with anti-infection outcome(P<0.05). The Monte Carlo model we built fits for the regimen prediction of hematonosis patients. We suggest giving sufficient dose by considering patients' pharmacokinetic parameters as well as MIC of separated MRSA, which will greatly assist with dosage optimization and individualized drug administration. |
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