Optimised dosing of vancomycin in critically ill Indigenous Australian patients with severe sepsis

Two Innovative Approaches to Optimize Vancomycin Dosing Using Estimated AUC after First Dose: Validation Using Data Generated from Population PK Model Coupled with Monte-Carlo Simulation and Comparison with the First-Order PK Equation Approach

The revised consensus guidelines for optimizing vancomycin doses suggest that maintaining the area under the concentration-time curve to minimal inhibitory concentration ratio (AUC/MIC) of 400–600 mg·h/L is the target pharmacokinetic/pharmacodynamic (PK/PD) index for efficacy. AUC-guided dosing approach uses a first-order pharmacokinetics (PK) equation to estimate AUC using two samples obtained at steady state and one-compartment model, which can cause inaccurate AUC estimation and fail to achieve the effective PK/PD target early in therapy (days 1 and 2). To achieve an efficacy target from the third or fourth dose, two innovative approaches (Method 1 and Method 2) to estimate vancomycin AUC at steady state (AUCSS) using two-compartment model and three or four levels after the first dose are proposed. The feasibility of the proposed methods was evaluated and compared with another published dosing algorithm (Method 3), which uses two samples and a one-compartment approach. Monte Carlo simulation was performed using a well-established population PK model, and concentration-time profiles for virtual patients with various degrees of renal function were generated, with 1000 subjects per group. AUC extrapolated to infinity (AUC0–∞) after the first dose was estimated using the three methods, whereas reference AUC (AUCref) was calculated using the linear-trapezoidal method at steady state after repeated doses. The ratio of AUC0–∞: AUCref and % bias were selected as the indicators to evaluate the accuracy of three methods. Sensitivity analysis was performed to examine the influence of change in each sampling time on the estimated AUC0–∞ using the two proposed approaches. For simulated patients with various creatinine clearance, the mean of AUC0–∞: AUCref obtained from Method 1, Method 2 and Method 3 ranged between 0.98 to 1, 0.96 to 0.99, and 0.44 to 0.69, respectively. The mean bias observed with the three methods was −0.10% to −2.09%, −1.30% to −3.59% and −30.75% to −55.53%, respectively. The largest mean bias observed by changing sampling time while using Method 1 and Method 2 were −4.30% and −10.50%, respectively. Three user-friendly and easy-to-use excel calculators were built based on the two proposed methods. The results showed that our approaches ensured sufficient accuracy and achieved target PK/PD index early and were superior to the published methodologies. Our methodology has the potential to be used for vancomycin dose optimization and can be easily implemented in clinical practice.

Clinical Practice Guidelines for Therapeutic Drug Monitoring of Vancomycin in the Framework of Model-Informed Precision Dosing: A Consensus Review by the Japanese Society of Chemotherapy and the Japanese Society of Therapeutic Drug Monitoring

Background: To promote model-informed precision dosing (MIPD) for vancomycin (VCM), we developed statements for therapeutic drug monitoring (TDM). Methods: Ten clinical questions were selected. The committee conducted a systematic review and meta-analysis as well as clinical studies to establish recommendations for area under the concentration-time curve (AUC)-guided dosing. Results: AUC-guided dosing tended to more strongly decrease the risk of acute kidney injury (AKI) than trough-guided dosing, and a lower risk of treatment failure was demonstrated for higher AUC/minimum inhibitory concentration (MIC) ratios (cut-off of 400). Higher AUCs (cut-off of 600 μg·h/mL) significantly increased the risk of AKI. Although Bayesian estimation with two-point measurement was recommended, the trough concentration alone may be used in patients with mild infections in whom VCM was administered with q12h. To increase the concentration on days 1–2, the routine use of a loading dose is required. TDM on day 2 before steady state is reached should be considered to optimize the dose in patients with serious infections and a high risk of AKI. Conclusions: These VCM TDM guidelines provide recommendations based on MIPD to increase treatment response while preventing adverse effects.

Relationship Between Mean Vancomycin Trough Concentration and Mortality in Critically Ill Patients: A Multicenter Retrospective Study

Background: It remains unclear whether the mean vancomycin trough concentration (VTC) derived from the entire course of therapy is of potential benefit for critically ill patients. This study was conducted to explore the association between mean serum VTC and mortality in intensive care units (ICUs). Methods: 3,603 adult patients with two or more VTC records after receiving vancomycin treatment in the eICU Collaborative Research Database were included in this multicenter retrospective cohort study. Mean VTC was estimated using all measured VTCs and investigated as a continuous and categorical variable. Patients were categorised into four groups according to mean VTC: <10, 10-15, 15-20, and >20 mg/L. Multivariable logistic regression and subgroup analyses were performed to investigate the relationship of mean VTC with mortality. Results: After adjusting for a series of covariates, logistic regression analyses indicated that mean VTC, as a continuous variable, was positively correlated with ICU (odds ratio, 1.038, 95% confidence interval, [1.014-1.063]) and hospital (1.025 [1.005-1.046]) mortalities. As a categorical variable, mean VTC of 10-15 mg/L was not associated with reduced ICU (1.705 [0.975-2.981]) and hospital (1.235 [0.829-1.841]) mortalities. Mean VTC of 15-20 mg/L was not correlated with a lower risk of hospital mortality (1.370 [0.924-2.029]). Moreover, mean VTCs of 15-20 and >20 mg/L were significantly associated with higher ICU mortality (1.924 [1.111-3.332]; 2.428 [1.385-4.258]), and mean VTC of >20 mg/L with higher hospital mortality (1.585 [1.053-2.387]) than mean VTC of <10 mg/L. Similar results were observed in patients with different Acute Physiology and Chronic Health Evaluation IV score, creatinine clearance, age, and body mass index subgroups. Conclusion: Mean VTC was not associated with reduced ICU/hospital related mortality. Our results suggested that VTC monitoring might not guarantee vancomycin efficacy for ICU patients.

An evaluation on the association of vancomycin trough concentration with mortality in critically ill patients: A multicenter retrospective study

To determine the impact of initial vancomycin trough concentration (VTC) on mortality in adult patients in the intensive care unit (ICU) undergoing vancomycin therapy. During their first ICU stay, patients with initial VTC records after vancomycin treatment were recruited from the eICU Collaborative Research Database to this multicenter retrospective cohort study, and classified into four groups according to VTC: less than 10, 10–15, 15–20, and greater than 20 mg/L. Multivariable logistic regression and sensitivity analyses were performed to explore the association of VTC, as a continuous and categorical variable, with mortality. This study enrolled 7220 patients from 335 different ICUs at 208 hospitals. Multivariable logistic regression models indicated that VTC was positively correlated with ICU (odds ratio [OR], 1.028, 95% confidence interval [CI], 1.019–1.037) and hospital (OR 1.028, 95% CI, 1.020–1.036) mortalities. Moreover, compared with VTC less than 10 mg/L, VTCs of 10–15, 15–20, and greater than 20 mg/L were associated with a higher risk of ICU mortality (OR, 1.330, 95% CI, 1.070–1.653; OR, 1.596, 95% CI, 1.265–2.015; abd OR, 1.875, 95% CI, 1.491–2.357, respectively), and VTCs of 15–20 and greater than 20 mg/L were also correlated with increased hospital mortality (OR, 1.482, 95% CI, 1.225–1.793; and OR, 1.831, 95% CI, 1.517–2.210, respectively). Similar results persisted in patients with different Acute Physiology and Chronic Health Evaluation Ⅳ scores, creatinine clearance levels, ages, and body mass indexes. Our findings indicated a potential relationship of initial VTC with ICU and hospital mortalities in patients in the ICU. However, due to the retrospective nature of this study, future prospective studies or randomized controlled trials are needed to validate those results.

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.

Why we should sample sparsely and aim for a higher target: Lessons from model-based therapeutic drug monitoring of vancomycin in intensive care patients

Aims

To explore the optimal data sampling scheme and the pharmacokinetic (PK) target exposure on which dose computation is based in the model‐based therapeutic drug monitoring (TDM) practice of vancomycin in intensive care (ICU) patients.

Methods

We simulated concentration data for 1 day following four sampling schemes, C_min, C_max + C_min, C_max + C_{mid‐interval} + C_min, and rich sampling where a sample was drawn every hour within a dose interval. The datasets were used for Bayesian estimation to obtain PK parameters, which were used to compute the doses for the next day based on five PK target exposures: AUC₂₄ = 400, 500, and 600 mg·h/L and C_min = 15 and 20 mg/L. We then simulated data for the next day, adopting the computed doses, and repeated the above procedure for 7 days. Thereafter, we calculated the percentage error and the normalized root mean square error (NRMSE) of estimated against “true” PK parameters, and the percentage of optimal treatment (POT), defined as the percentage of patients who met 400 ≤ AUC₂₄ ≤ 600 mg·h/L and C_min ≤ 20 mg/L.

Results

PK parameters were unbiasedly estimated in all investigated scenarios and the 6‐day average NRMSE were 32.5%/38.5% (CL/V, where CL is clearance and V is volume of distribution) in the trough sampling scheme and 27.3%/26.5% (CL/V) in the rich sampling scheme. Regarding POT, the sampling scheme had marginal influence, while target exposure showed clear impacts that the maximum POT of 71.5% was reached when doses were computed based on AUC₂₄ = 500 mg·h/L.

Conclusions

For model‐based TDM of vancomycin in ICU patients, sampling more frequently than taking only trough samples adds no value and dosing based on AUC₂₄ = 500 mg·h/L lead to the best POT.

Vancomycin population pharmacokinetics for adult patients with sepsis or septic shock: are current dosing regimens sufficient?

PURPOSE

Vancomycin is commonly used for the management of severe infections; however, vancomycin dosing may be challenging in critically ill patients. This observational study aims to describe the population pharmacokinetics of vancomycin in adult patients with sepsis or septic shock.

METHODS

A single-centre retrospective review of adult patients with sepsis or septic shock receiving vancomycin with therapeutic drug monitoring was undertaken. Blood samples taken 1 h after the vancomycin infusion cessation and 30 min prior to the next dose were assayed using the Vitros Crea Slide method. Vancomycin concentrations determined on different days were included. A pharmacokinetic model was developed using Pmetrics for R. Monte Carlo dosing simulations were performed using the final model.

RESULTS

Vancomycin concentrations were available for 27 adult patients admitted to the intensive care unit with sepsis or septic shock. A one-compartment pharmacokinetic model with inter-occasion variability of clearance and volume of distribution before and after 72 h adequately described the data. Creatinine clearance normalized to body surface area was included as a covariate on vancomycin clearance. The clearance and volume of distribution within 72 h of admission were 7.29 L/h and 54.20 L, respectively. Monte Carlo simulations suggested that for patients with a creatinine clearance of ≥ 80 mL/min/1.73 m², vancomycin doses of ≥ 2 g every 8 h are required to consistently achieve key therapeutic targets.

CONCLUSIONS

Vancomycin doses ≥ 2 g every 8 h in adult patients with sepsis or septic shock with a creatinine clearance ≥ 80 mL/min/1.73 m² are likely needed to achieve an optimal therapeutic exposure.