Population pharmacokinetic model of Vancomycin based on therapeutic drug monitoring data in critically ill septic patients

Factors Affecting Vancomycin Trough Concentration; a Population Pharmacokinetic Model in Non-Critical Care Saudi Patients

Background and Objective

Vancomycin is commonly prescribed in treatment of methicillin-resistant Staphylococcus aureus infections. While, vancomycins' pharmacokinetic vary among older patients, there is a paucity of data regarding specific characteristics influencing pharmacokinetics in Saudi adult patients. This study aims to establish a population-pharmacokinetic (Pop-PK) model for vancomycin in patients admitted to medical wards, with the focus on identification of patient characteristics influencing vancomycin trough concentrations.

Methods

A multicenter retrospective study was conducted involving patients aged ≥40 years admitted to medical wards in the Eastern Province, Saudi Arabia and initiated on vancomycin, between January to December 2022. Non-linear mixed-effects modelling (Monolix) was employed to develop the Pop-PK model. A base model was selected based on the Akaike information criterion. Covariates considered included age, sex, body weight, C-reactive protein (CRP), serum creatinine, creatinine clearance (CrCl), and albumin levels. A P-value of <0.05 was considered statistically significant for inclusion of covariates in the final model by stepwise addition. The simulation performance of the model was assessed by visual predictive check plot. The final model was simulated using Simulx software to assess the effect of the included covariates on vancomycin trough concentration.

Results

A total of 172 vancomycin trough concentrations from 124 patients were analyzed. The final Pop-PK model characterized vancomycin trough concentrations was one compartment distribution with linear elimination. CrCl and CRP were the only covariates included in the final model, as they reduced the between-subject variability (BSV) for clearance (from 173% to 81%). The simulated model demonstrated that high CRP value and low CrCl contributed to increased vancomycin trough concentrations.

Conclusion

This study highlights large BSV in trough concentrations among patients and emphasizes the influencing of CrCl and CRP on vancomycin pharmacokinetics in medical care settings.

Selecting the Best Pharmacokinetic Models for a Priori Model-Informed Precision Dosing with Model Ensembling

BACKGROUND AND OBJECTIVE

When utilizing population pharmacokinetic (popPK) models for a priori dosage individualization, selecting the best model is crucial to obtain adequate doses. We developed and evaluated several model-selection and ensembling methods, using external evaluation on the basis of therapeutic drug monitoring (TDM) samples to identify the best (set of) models per patient for a priori dosage individualization.

METHODS

PK data and models describing both hospitalized patients (n = 134) receiving continuous vancomycin (26 models) and patients (n = 92) receiving imatinib in an outpatient setting (12 models) are included. Target attainment of four model-selection methods was compared with standard dosing: the best model based on external validation, uninformed model ensembling, model ensembling using a weighting scheme on the basis of covariate-stratified external evaluation, and model selection using covariates in decision trees that were subsequently ensembled.

RESULTS

Overall, the use of PK models improved the proportion of patients exposed to concentrations within the therapeutic window for both cohorts. Relative improvement of proportion on target for best model, unweighted, weighted, and decision trees were - 7.0%, 2.3%, 11.4%, and 37.0% (vancomycin method-development); 23.2%, 7.9%, 15.6%, and, 77.2% (vancomycin validation); 40.7%, 50.0%, 59.5%, and 59.5% (imatinib method-development); and 19.0%, 28.5%, 38.0%, and 23.8% (imatinib validation), respectively.

CONCLUSIONS

The best (set of) models per patient for a priori dosage individualization can be identified using a relatively small set of TDM samples as external evaluation. Adequately performing popPK models were identified while also excluding poor-performing models. Dose recommendations resulted in more patients within the therapeutic range for both vancomycin and imatinib. Prospective validation is necessary before clinical implementation.

Thrombocytopenia risks in ARDS COVID-19 patients treated with high-dose linezolid during vvECMO therapy: an observational study

Patients treated with ECMO are at great risk of nosocomial infections, and around 10% of isolates are gram-positive pathogens. Linezolid (LZD) is effective in the treatment of these infections but appropriate dosing is challenging. The aim was to evaluate the occurrence of thrombocytopenia during ECMO when treated with LZD. An LZD trough concentration of 8 mg/L was set as the cutoff value for thrombocytopenia occurrence among critically ill patients who received parenteral LZD therapy at a dose of 600 mg every 8 h during ECMO. Eleven patients were included in this prospective observational study. Median LZD trough concentrations were 7.85 (interquartile range (IQR), 1.95-11) mg/L. Thrombocytopenia was found in 81.8% of patients. Based on the median LZD trough concentrations cutoff value, patients were divided into two groups, 1.95 (IQR, 0.91-3.6) and 10.3 (IQR, 9.7-11.7) mg/L, respectively. Median platelet values differed significantly between groups on admission, ECMO day 0, ECMO day 1, and LZD sampling day [194 and 152.5, (p < 0.05)], [113 and 214, (p < 0.05)], [76 and 147.5, (p < 0.01)], and [26 and 96.5, (p < 0.01)], respectively. Duration of LZD therapy was similar between the groups. Significant platelet reduction was observed in both groups, emphasizing the need for closer monitoring to prevent LZD-associated thrombocytopenia.

Risk Factors Associated with Antibiotic Exposure Variability in Critically Ill Patients: A Systematic Review

(1) Background: Knowledge about the behavior of antibiotics in critically ill patients has been increasing in recent years. Some studies have concluded that a high percentage may be outside the therapeutic range. The most likely cause of this is the pharmacokinetic variability of critically ill patients, but it is not clear which factors have the greatest impact. The aim of this systematic review is to identify risk factors among critically ill patients that may exhibit significant pharmacokinetic alterations, compromising treatment efficacy and safety. (2) Methods: The search included the PubMed, Web of Science, and Embase databases. (3) Results: We identified 246 observational studies and ten clinical trials. The most studied risk factors in the literature were renal function, weight, age, sex, and renal replacement therapy. Risk factors with the greatest impact included renal function, weight, renal replacement therapy, age, protein or albumin levels, and APACHE or SAPS scores. (4) Conclusions: The review allows us to identify which critically ill patients are at a higher risk of not reaching therapeutic targets and helps us to recognize the extensive number of risk factors that have been studied, guiding their inclusion in future studies. It is essential to continue researching, especially in real clinical practice and with clinical outcomes.

Population Pharmacokinetic of Vancomycin Administered by Continuous Infusion in Critically Ill Patients

INTRODUCTION

Administration of vancomycin dose by continuous infusion (CI) according to population pharmacokinetic (Pop Pk) models is highly recommended in critically ill patients who exhibit pathophysiological changes.

OBJECTIVE

The objective of this study was to develop and validate a Pop Pk model of vancomycin administered by CI in critically ill patients with normal and impaired renal functions.

METHODS

The Pop Pk study was performed using a nonparametric approach (Pmetrics*). The influence of covariates (gender, age, weight, height, and creatinine clearance [Cr-Cl]) was tested on the model's Pk parameters. The performance of the final model was assessed using an external dataset.

RESULTS

A one-compartment model (volume of distribution [Vd], elimination from compartment [Ke]) was found to show a good prediction performance. The influence of covariates has shown that age and Cr-Cl affected significantly Vd and Ke, respectively. The distribution of simulated vancomycin clearance (CLv) according to different renal function levels showed a negative correlation between CLv and the severity of the renal impairment. The internal validation of the final model showed that the plot of individual-predicted concentration versus observed concentration resulted in r2 = 0.86 in the final model. The external validation of the final model showed an acceptable predictive performance.

CONCLUSION

We developed a Pop Pk model for vancomycin administered by CI in critically ill patients. A significant impact of Cr-Cl and different stages of renal failure on CLv has been demonstrated. The establishment of an individualized proposal dose based on this model may be helpful to achieve the target range which is critical in optimizing the efficacy and safety of this antibiotic.

Clinical benefits of therapeutic drug monitoring of vancomycin therapy in patients with postoperative intracerebral hemorrhage: a retrospective cohort study

OBJECTIVE

The objective of this study was to investigate the clinical efficacy and safety of conducting therapeutic drug monitoring (TDM) of vancomycin in patients with postoperative intracerebral haemorrhage.

METHODS

We conducted a retrospective analysis of 435 patients who experienced postoperative cerebral haemorrhage and were treated with vancomycin in the Department of Neurosurgery of Inner Mongolia Autonomous Region People's Hospital from January 2017 to December 2021. Patients were then matched using the propensity score matching method in a ratio of 1:1. Ninety-two pairs of cases were successfully matched, and the data before and after performing vancomycin TDM were analysed.

RESULTS

After PSM, the baseline data of the two groups were balanced. There were no significant differences in the 14-day mortality and length of hospital stay (p>0.05) between the two groups. Compared with the non-TDM group, the TDM group had a higher proportion of patients with normal white blood cells (83.7% vs 56.5%, p=0.000), neutrophil count (57.6% vs 25.0%, p=0.000) and attaining desirable reductions of 80% in procalcitonin (65.2% vs 10.9%, p=0.000) and C-reactive protein (78.3% vs 41.3%, p=0.000) levels. At US$15.82 per additional TDM, TDM significantly promoted patient outcomes, as seen in improvements in the proportion of patients attaining desirable levels of white blood cells, neutrophil count, procalcitonin and C-reactive protein.

CONCLUSIONS

Vancomycin TDM is a safe and effective approach for the treatment of patients with postoperative intracerebral haemorrhage. The empirical use of TDM of vancomycin significantly improved normal values of white blood cells and neutrophil count, achieved desirable reductions of 80% in procalcitonin and C-reactive protein, and reduced nephrotoxicity in patients with postoperative intracerebral haemorrhage.

Age-Related Differences in Vancomycin-Associated Nephrotoxicity and Efficacy in Methicillin-Resistant Staphylococcus aureus Infection: A Comparative Study between Elderly and Adult Patients

Elderly patients (age ≥ 65 years) are susceptible to methicillin-resistant Staphylococcus aureus (MRSA) infections, with potential for more adverse treatment outcomes or complications compared to younger adults (18-64 years). This study compared vancomycin-associated nephrotoxicity and efficacy in elderly and adult patients and investigated the correlation between vancomycin pharmacokinetic/pharmacodynamic (PK/PD) indices and clinical outcomes. A prospective study was conducted in 10 hospitals in Shanghai from October 2012 to November 2019. A total of 164 patients with MRSA infections were enrolled, including 83 elderly and 81 adult patients. Vancomycin therapeutic drug monitoring (TDM) was performed in all patients, indicating significantly higher vancomycin trough concentrations (Ctrough), 24-h area under the curve (AUC24) values, and AUC24/minimum inhibitory concentration (AUC24/MIC) values in elderly patients compared to adult patients. The incidence of vancomycin-associated nephrotoxicity was nearly three times higher in elderly patients (18.1% vs. 6.2%, p = 0.020), despite similar clinical and microbiological efficacy. Of particular importance, a Ctrough > 20 mg/L was found as an independent factor of nephrotoxicity in elderly patients. Further analysis of patients with an estimated glomerular filtration rate (eGFR) > 60 mL/min/1.73 m2 also revealed that elderly patients had significantly higher vancomycin-related PK/PD indices and more nephrotoxicity than adult patients. In conclusion, elderly patients receiving vancomycin therapy face a higher risk of nephrotoxicity, which requires close vancomycin TDM, especially when the Ctrough exceeds 20 mg/L.

Population Pharmacokinetic Model of Linezolid and Probability of Target Attainment in Patients with COVID-19-Associated Acute Respiratory Distress Syndrome on Veno-Venous Extracorporeal Membrane Oxygenation-A Step toward Correct Dosing

During veno-venous extracorporeal membrane oxygenation (vv ECMO) therapy, antimicrobial drugs are frequently used, and appropriate dosing is challenging due to there being limited data to support the dosage. Linezolid is effective against multidrug-resistant Gram-positive pathogens frequently isolated in ECMO patients. In total, 53 steady-state linezolid levels were obtained following 600 mg intravenous (IV) injections every 8 h, and these were used to develop a population pharmacokinetic (PopPK) model in patients with COVID-19-associated acute respiratory distress syndrome (CARDS) on vv ECMO. The data were analyzed using a nonlinear mixed-effects modelling approach. Monte Carlo simulation generated 5000 patients' individual PK parameters and corresponding concentration-time profiles using the PopPK model, following the administration of 600 mg/8 h (a higher-than-standard dosing) and 600 mg/12 h (standard). The probabilities of pharmacokinetic/pharmacodynamic (PK/PD) target attainment (PTA) and the cumulative fraction of responses (CFR) for three pathogens were calculated and compared between the two dosing scenarios. Linezolid 600 mg/8 h was predicted to achieve greater than or equal to 85%Tf>MIC in at least 90% of the patients with CARDS on vv ECMO compared to only approximately two thirds of the patients after dosing every 12 h at a minimal inhibitory concentration (MIC) of 2 mg/L. In addition, for the same MIC, fAUC24/MIC ≥ 80 was achieved in almost three times the number of patients following an 8-h versus a 12-h interval. PopPK simulation predicted that a significantly higher proportion of the patients with CARDS on vv ECMO would achieve the PK/PD targets following the 8-h dosing interval compared to standard linezolid dosing. Nevertheless, the safety concern, in particular, for thrombocytopenia, with higher-than-standard linezolid dosage is reasonable, and consequently, monitoring is essential.

Population Pharmacokinetics and Model-Based Dose Optimization of Vancomycin in Sudanese Adult Patients with Renal Impairment

Purpose

The study aimed to perform a population pharmacokinetic (PK) analysis to obtain vancomycin PK parameter estimates in Sudanese adult patients. The population PK model is then applied to perform model-based dose optimization.

Patients and Methods

Data were collected through a retrospective, single-center, observational cohort study performed in Aliaa Specialist Hospital, Khartoum, Sudan. A population PK model was developed using the MonolixSuite 2020R1 to explore the potential effects of demographics and laboratory covariates on vancomycin PK. Monte Carlo simulations were performed to optimize dosage regimens as a function of creatinine clearance (CLcr) and virtual patients were partitioned into five CLcr groups.

Results

We retrospectively collected 194 vancomycin plasma concentrations from 99 adults. The median (interquartile range) for age (years) and CLcr (mL/min) were 65 (50-75) and 12.7 (5.52-25.78), respectively. Vancomycin PK data were best fitted using a one-compartment model with linear elimination. The estimates of clearance and volume of distribution were 2.02 L/h and 65 L, respectively. CLcr was identified as the main covariate explaining the PK variability in vancomycin CL. CL significantly decreased with decreasing CLcr. For the five CLcr groups evaluated, a tailored vancomycin daily maintenance dose (using patients' CLcr) ranged from 200 to 1650 mg. Overall, simulations showed that 45% (CI; 41.11-47.36%) of patients would achieve a target AUC with the suggested dosages.

Conclusion

A population PK model of vancomycin was developed using data obtained from adult Sudanese patients. Model-based dose optimization can aid clinicians in selecting initial vancomycin doses that will maximize the likelihood of a favorable treatment response.

Population pharmacokinetics of antibacterial agents in the older population: a literature review

INTRODUCTION

Older individuals face an elevated risk of developing bacterial infections. The optimal use of antibacterial agents in this population is challenging because of age-related physiological alterations, changes in pharmacokinetics (PK) and pharmacodynamics (PD), and the presence of multiple underlying diseases. Therefore, population pharmacokinetics (PPK) studies are of great importance for optimizing individual treatments and prompt identification of potential risk factors.

AREA COVERED

Our search involved keywords such as 'elderly,' 'old people,' and 'geriatric,' combined with 'population pharmacokinetics' and 'antibacterial agents.' This comprehensive search yielded 11 categories encompassing 28 antibacterial drugs, including vancomycin, ceftriaxone, meropenem, and linezolid. Out of 127 studies identified, 26 (20.5%) were associated with vancomycin, 14 (11%) with meropenem, and 14 (11%) with piperacillin. Other antibacterial agents were administered less frequently.

EXPERT OPINION

PPK studies are invaluable for elucidating the characteristics and relevant factors affecting the PK of antibacterial agents in the older population. Further research is warranted to develop and validate PPK models for antibacterial agents in this vulnerable population.

Population pharmacokinetic model of vancomycin in postoperative neurosurgical patients

Objective: Vancomycin is commonly used in postoperative neurosurgical patients for empirical anti-infective treatment due to the low success rate of bacterial culture in cerebrospinal fluid (about 20%) and the high mortality of intracranial infection. At conventional doses, the rate of target achievement for vancomycin trough concentration is low and the pharmacokinetics of vancomycin varies greatly in these patients, which often leads to treatment failure. The objective of this study was to establish a population pharmacokinetic (PPK) model of vancomycin in postoperative neurosurgical patients for precision medicine.

Method: A total of 895 vancomycin plasma concentrations from 560 patients (497 postoperative neurosurgical patients) were retrospectively collected. The model was analyzed by nonlinear mixed effects modeling method. One-compartment model and mixed residual model was employed. The influence of covariates on model parameters was tested by forward addition and backward elimination. Goodness-of-fit, bootstrap and visual predictive check were used for model evaluation. Monte Carlo simulations were employed for dosing strategies with AUC₂₄ targets 400–600.

Result: Estimated glomerular filtration rate (eGFR), body weight (BW) and mannitol had significant influence on vancomycin clearance (CL). eGFR(mL/min)=144×(Scr/a)b×0.993age, for female, a = 0.7, Scr ≤ 0.7 mg/dl, b = −0.329, Scr > 0.7 mg/dl, b = −1.209; for male, a = 0.9, Scr ≤ 0.9 mg/dl, b = −0.411, Scr > 0.9 mg/dl, b = −1.210. Vancomycin clearance was accelerated when co-medicated with mannitol and increased with eGFR and BW. In the final model, the population typical value is 7.98 L/h for CL and 60.2 L for apparent distribution volume, CL (L/h)=7.98×(eGFR/115.2)0.8×(BW/70)0.3×eA, where A = 0.13 when co-medicated with mannitol, otherwise A = 0. The model is stable and effective, with good predictability.

Conclusion: In postoperative neurosurgical patients, a higher dose of vancomycin may be required due to the augmented renal function and the commonly used mannitol, especially in those with high body weight. Our vancomycin PPK model could be used for individualized treatment in postoperative neurosurgical patients.

Dose Tailoring of Vancomycin Through Population Pharmacokinetic Modeling Among Surgical Patients in Pakistan

Background: Vancomycin is a narrow therapeutic agent, and it is necessary to optimize the dose to achieve safe therapeutic outcomes. The purpose of this study was to identify the significant covariates for vancomycin clearance and to optimize the dose among surgical patients in Pakistan. Methods: Plasma concentration data of 176 samples collected from 58 surgical patients treated with vancomycin were used in this study. A population pharmacokinetic model was developed on NONMEM^® using plasma concentration-time data. The effect of all available covariates was evaluated on the pharmacokinetic parameters of vancomycin by stepwise covariate modeling. The final model was evaluated using bootstrap, goodness-of-fit plots, and visual predictive checks. Results: The pharmacokinetics of vancomycin followed a one-compartment model with first-order elimination. The vancomycin clearance (CL) and volume of distribution (Vd) were 2.45 L/h and 22.6 l, respectively. Vancomycin CL was influenced by creatinine clearance (CRCL) and body weight of the patients; however, no covariate was significant for its effect on the volume of distribution. Dose tailoring was performed by simulating dosage regimens at a steady state based on the CRCL of the patients. The tailored doses were 400, 600, 800, and 1,000 mg for patients with a CRCL of 20, 60, 100, and 140 ml/min, respectively. Conclusion: Vancomycin CL is influenced by CRCL and body weight of the patient. This model can be helpful for the dose tailoring of vancomycin based on renal status in Pakistani patients.

Concept and utility of population pharmacokinetic and pharmacokinetic/pharmacodynamic models in drug development and clinical practice

Due to frequent clinical trial failures and consequently fewer new drug approvals, the need for improvement in drug development has, to a certain extent, been met using model-based drug development. Pharmacometrics is a part of pharmacology that quantifies drug behaviour, treatment response and disease progression based on different models (pharmacokinetic - PK, pharmacodynamic - PD, PK/PD models, etc.) and simulations. Regulatory bodies (European Medicines Agency, Food and Drug Administration) encourage the use of modelling and simulations to facilitate decision-making throughout all drug development phases. Moreover, the identification of factors that contribute to variability provides a basis for dose individualisation in routine clinical practice. This review summarises current knowledge regarding the application of pharmacometrics in drug development and clinical practice with emphasis on the population modelling approach.

Vancomycin Area under the Curve and Pharmacokinetic Parameters during the First 24 Hours of Treatment in Critically Ill Patients using Bayesian Forecasting

Background

Currently, the achievement of the target area under the curve (AUC)/minimum inhibitory concentration ratio during the first 24 - 48 h of treatment is associated with reduced 30-day mortality and greater microbiological eradication in patients with methicillin-resistant Staphylococcus aureus bacteremia. This study aimed to determine the AUC and pharmacokinetic parameters on the first day of vancomycin administration based on the Bayesian theorem to optimize the dosing regimen in critically ill patients.

Materials and Methods

This retrospective study included participants meeting the following criteria: 1) ≥18 years old; 2) receipt of at least one dose of vancomycin; 3) measurement of 2 vancomycin serum concentrations during the first 24 h of treatment; and 4) an intensive care unit admission, mechanical ventilator use, or an Acute Physiology and Chronic Health Evaluation II score >15 points. The AUC on day 1 of treatment and the estimated vancomycin pharmacokinetic parameters were measured using PrecisePK software based on the Bayesian theorem.

Results

We obtained 132 vancomycin concentrations from 66 patients. The vancomycin pharmacokinetic parameters were as follows: AUC_0-24, 571.09 (± standard deviation [SD] 188.62) mg/L·h; clearance (CL), 2.97 (± SD 1.81) L/h; volume of distribution (Vd), 50.60 (± SD 13.91) L; elimination rate constant, 0.062 (± SD 0.039) h⁻¹; and half-life, 18.19 (± SD 15.96) h. Focusing on the vancomycin loading dose, AUC_0-24 400 - 600 was achieved in 41.7, 46.1, 44.4, and 26.3% of patients with loading doses of <20, 20 – 24.9, 25 – 30, and >30 mg/kg, respectively. Whereas AUC_0-24 ≥521 was achieved in 50, 50, 77.8, and 84.2% of patients with loading doses of <20, 20 – 24.9, 25 – 30, and >30 mg/kg, respectively. The CL of vancomycin was correlated with creatinine CL, whereas the Vd of vancomycin was significantly correlated with age and body weight.

Conclusion

This study revealed that the higher Vd and CL values on the first day of vancomycin therapy were found in critically ill patients. Additionally, a higher vancomycin loading dose (25 – 30 mg/kg) might be required to achieve target of AUC_0-24 during early phase of administration for critically ill patients.

Population Pharmacokinetics of Vancomycin in Kidney Transplant Recipients: Model Building and Parameter Optimization

Background

Depending on the renal function of patients and many other influencing factors, studies on vancomycin pharmacokinetics show significant inter- and intra-individual variability. The present study was conducted using a population pharmacokinetics method to investigate the pharmacokinetic parameters and identified their influencing covariates for intravenous vancomycin in adult kidney transplant recipients.

Methods

The drug monitoring data included 56 adult renal transplant recipients who received intravenous vancomycin as prophylactic medication. The analysis was performed by a population approach with NONMEM. Data were collected mainly during the first week after transplantation. Monitoring of vancomycin trough concentration in blood was initiated mainly 3–5 days after the initial administration.

Results

The one-compartment open model was optimal and adequately described the data. Body weight (WT) and estimated glomerular filtration rate (GFR) were identified as significant covariates of the pharmacokinetic parameters CL and V of intravenous vancomycin in the kidney transplant patients. The typical values of vancomycin CL and V were 2.08 L h^-1 and 63.2 L, respectively. A dosage strategy scheme according to model results was also designed.

Conclusion

Both WT and GFR of the kidney transplant patients positively influence the pharmacokinetic parameters CL and V for intravenous vancomycin. Our population pharmacokinetic model provides a reference for vancomycin dosage adjustment in kidney transplant recipients.

Population Pharmacokinetic Modeling of Vancomycin in Thai Patients With Heterogeneous and Unstable Renal Function

BACKGROUND

Vancomycin is widely used to treat gram-positive bacterial infections. However, given significant interpatient variability in its pharmacokinetics, maintaining plasma concentrations is difficult within its characteristically narrow therapeutic window. This is especially challenging in patients with unstable renal function. Thus, the aim of this study was to develop a population pharmacokinetic model for vancomycin that is suitable for Thai patients with variable renal functions, including those with unstable renal function.

METHODS

Data from 213 patients, including 564 blood samples, were retrospectively collected; approximately 70% patients exhibited unstable renal function during vancomycin treatment. The model building group was randomly assigned 108 patients and the remaining 33 patients comprised the validation group. A population pharmacokinetic model was developed that incorporated drug clearance (CL) as a function of time-varying creatine clearance (CrCL). The predictive ability of the resulting population model was evaluated using the validation data set, including its ability to forecast serum concentrations within a Bayesian feedback algorithm.

RESULTS

A 2-compartment model with drug CL values that changed with time-varying CrCL adequately described vancomycin pharmacokinetics in the evaluated heterogeneous patient population with unstable renal function. Vancomycin CL was related to time-varying CrCL as follows: CL (t) = 0.11 + 0.021 × CrCL (t) (CrCL <120 mL/min. Using the population model, Bayesian estimation with at least one measured serum concentration resulted in a forecasting error of small bias (-2.4%) and adequate precision (31.5%).

CONCLUSIONS

In hospitals with a high incidence of unstable renal function, incorporating time-varying CrCL with Bayesian estimation and at least one measured drug concentration, along with frequent CrCL monitoring, improves the predictive performance of therapeutic drug monitoring of vancomycin.