Candidates for area under the concentration-time curve (AUC)-guided dosing and risk reduction based on analyses of risk factors associated with nephrotoxicity in vancomycin-treated patients

OBJECTIVES

Compared with vancomycin trough concentration (C_min)-guided dosing, area under the concentration-time curve (AUC)-guided dosing is associated with decreased acute kidney injury (AKI). However, whether C_min-guided or AUC-guided dosing should be used in patients other than those with serious MRSA infections remains uncertain. The purposes of this multicentre study were to identify risk factors for early- and late-phase vancomycin-induced AKI and to identify candidates for AUC-guided dosing, rather than C_min-guided dosing, who require a more accurate dose titration to reduce the AKI risk.

METHODS

A multivariate logistic regression analysis was applied to identify risk factors for AKI. Additionally, the cut‑off day for AKI onset, cut-off C_min for AKI, safe C_min for reduced AKI risk and probability of AKI were calculated.

RESULTS

In total, 8.4% (159/1882) of patients developed AKI. AKI occurred within the first 7 days of therapy (early phase) in the vast majority of patients. Significant risk factors for AKI during the early phase were identified as C_min > 20 mg/L, ICU stay, concurrent diuretic or piperacillin/tazobactam use, and pre-existing renal dysfunction. A temporarily elevated C_min (>15-20 mg/L) was not associated with a greater risk of AKI. In patients with risk factors, the cut-off C_min for AKI and the estimated safe C_min for reduced AKI risk were 18.8-21.0 mg/L and <11.7-13.5 mg/L, respectively.

CONCLUSION

Patients with known AKI risk factors require a low target C_min. The presence of several risk factors for AKI may indicate a need for more accurate dose titration using AUC-guided dosing.

Reduced nephrotoxicity with vancomycin therapeutic drug monitoring guided by area under the concentration-time curve against a trough 15-20 μg/mL concentration

Vancomycin is often employed as an antibacterial agent against Gram-positive bacteria, although dose-dependent nephrotoxicity is a concern. Although the risk may be reduced by therapeutic drug monitoring (TDM) guided by area under the concentration-time curve (an attempt to target an AUC > 400 μg•h/mL by Bayesian prediction: AUC₄₀₀-guided TDM), the clinical efficacy of AUC₄₀₀-guided TDM compared with trough concentration-guided TDM within 15-20 μg/mL (Trough_15-20-guided TDM) has yet to be determined. We aimed to retrospectively evaluate the difference in the incidence rate of acute kidney injury (AKI), classified according to the Acute Kidney Injury Network, between these TDM groups. Individual AUC in the AUC₄₀₀-guided TDM group was calculated by Bayesian prediction using trough and peak concentrations (within 3 h after the end of infusion). The AKI incidence in the Trough_15-20-guided TDM group was 28.8% (15/52 patients) compared with an AKI incidence in the AUC₄₀₀-guided TDM group of 9.1% (2/22 patients). Application of AUC₄₀₀-guided TDM was identified as an independent factor for avoiding the incidence of AKI by Cox hazard regression analysis [hazard ratio = 0.168, 95% confidence interval (CI) 0.034-0.839] and logistic regression analysis (odds ratio = 0.037, 95% CI 0.003-0.285). As the estimated glomerular filtration rate (eGFR) improved, the surrogate target trough concentration for an AUC > 400 μg•h/mL was lowered (intercept 15.0074, slope -0.0598). In conclusion, AUC₄₀₀-guided TDM may be superior to Trough_15-20-guided TDM for the reduction of nephrotoxicity during vancomycin therapy.

Impact of area under the concentration-time curve to minimum inhibitory concentration ratio on vancomycin treatment outcomes in methicillin-resistant Staphylococcus aureus bacteraemia

There have been few clinical studies on the association between the vancomycin 24-h area under the concentration-time curve (AUC24) to minimum inhibitory concentration (MIC) ratio and vancomycin treatment outcomes in methicillin-resistant Staphylococcus aureus (MRSA) infections. To examine this association and to establish a suitable cut-off value for AUC24/MIC, a multicentre prospective observational study was conducted in patients with MRSA bacteraemia. Data were collected on all patients aged ≥18 years with MRSA bacteraemia treated with vancomycin for ≥72 h without dialysis. The MIC was determined by broth microdilution (BMD) and Etest. Treatment failure was defined as (i) 30-day mortality, (ii) persistent bacteraemia (≥7 days) and (iii) recurrence (≤30 days after completion of therapy). AUC24 was estimated by a Bayesian approach based on individual vancomycin concentrations. The AUC24/MIC cut-off value for differentiating treatment success and failure was calculated by Classification and Regression Tree (CART) analysis. In total, 117 patients were enrolled, among which vancomycin treatment failure occurred in 38 (32.5%). In univariate analysis, high vancomycin MIC and low trough levels were unrelated to treatment outcomes. In the CART analysis, low vancomycin AUC24/MIC [<392.7 (BMD) and <397.2 (Etest)] was associated with treatment failure. In multivariate analysis, low AUC24/MIC was a risk factor for treatment failure [adjusted odds ratio (aOR)=3.50, 95% confidence interval (CI) 1.39-8.82 by BMD; aOR=5.61, 95% CI 2.07-15.24 by Etest]. AUC24/MIC is associated with vancomycin treatment outcomes in MRSA bacteraemia, and seeking individualised AUC24/MIC ratios above target (>400) may improve treatment outcomes.

Area under the concentration-time curve to minimum inhibitory concentration ratio as a predictor of vancomycin treatment outcome in methicillin-resistant Staphylococcus aureus bacteraemia

There have been few clinical studies on the association between the 24-h area under the concentration-time curve (AUC24) to minimum inhibitory concentration (MIC) ratio and vancomycin treatment outcomes in methicillin-resistant Staphylococcus aureus (MRSA) infections. Patients with MRSA bacteraemia between July 2009 and January 2012 were analysed retrospectively. All adult patients treated with vancomycin for ≥72 h without dialysis were included. The MIC was determined by Etest and broth microdilution (BMD). Initial steady-state AUC24 was estimated using a Bayesian model, and the AUC24/MIC cut-off value for differentiating treatment success and failure was calculated by classification and regression tree (CART) analysis. In total, 76 patients were enrolled; vancomycin treatment failure occurred in 20 patients (26.3%). Catheter-related infection was the most frequent (35.5%), followed by surgical site infection (26.3%), whilst 25 (32.9%) had complicated infections. In univariate analysis, decreased MRSA vancomycin susceptibility (MIC≥1.5 mg/L) and vancomycin trough levels (15-20 mg/L) were not associated with treatment outcomes. In the CART analysis, low initial vancomycin AUC24/MIC (<430 by Etest; <398.5 by BMD) was associated with a higher treatment failure rate (50.0% vs. 25.0%, P=0.039 by Etest; 45.0% vs. 23.2%; P=0.065 by BMD). In multivariate analysis, low initial vancomycin AUC24/MIC was a significant risk factor for treatment failure [adjusted odds ratio (aOR)=4.39, 95% confidence interval (CI), 1.26-15.35 by Etest; aOR=3.73, 95% CI 1.10-12.61 by BMD]. In MRSA bacteraemia, a low initial vancomycin AUC24/MIC is an independent risk factor for vancomycin treatment failure.