Evaluation of the Relationship Between Elevated Vancomycin Trough Concentrations and Increased Efficacy and/or Toxicity:

Optimization of an empiric vancomycin dosing algorithm for improved target concentration attainment in patients with thermal injury

OBJECTIVE

Vancomycin empirical dosing studies in thermally injured patients have netted low successful target attainment and most excluded renal dysfunction, limiting applicability. In a previous study, the authors performed a retrospective analysis of 124 patients' measured pharmacokinetic parameters to calculate optimal dose and interval for intermittent infusion regimens and find predictors of clearance and total daily dose. The objective of this study was to improve the accuracy of attaining goal therapeutic targets with initial vancomycin regimens in patients with thermal injury through retrospective modeling.

METHODS

In this phase 2 study, variables collected and calculated regimens in phase 1 were utilized to try and create an improved empiric vancomycin dosing algorithm in patients with thermal injury. Logistic regression was utilized to determine best predictors of dosing vancomycin every 6 and 8h. The strongest models were built as individual algorithms and tested for accuracy of target attainment. Each algorithm produced a regimen for each patient that was then tested utilizing each patient's actual measured pharmacokinetic parameters.

RESULTS

Univariable logistic regression of 41 variables identified 27 and 23 to be predictive of dosing every 8 or 6h, respectively. The most predictive multivariable model for dosing every 8h consisted of creatinine clearance (CrCl)≥80ml/min, Acute Kidney Injury Network classification <1, and total body surface area burned≥10 percent. For dosing every 6h, CrCl≥80ml/min, age≤40years old, days since injury≤6, and serum creatinine (SCr)≤0.8 were most predictive. Based on the top 5 multivariable models for each dosing interval, 7 algorithms were built to produce recommended regimens. The highest performing algorithm resulted in trough concentrations of <10mg/L (23%), 10-20mg/L (65%), 15-20mg/L (26%), and >20mg/L (11%); area under the concentration curve (AUC)>400mghr/L (83%); and AUC >400mghr/L without having a trough >20mg/L (72%).

CONCLUSIONS

The algorithm that resulted in the highest target attainment without overdosing recommended 15mg/kg dosed every 24h for CrCl≥30, every 12h for CrCl 31-79, every 8h for patients with CrCl≥80ml/min, and every 6h only if the patient with a CrCl≥80ml/min is also≤40 years old and has a SCr≤0.8. Caution is warranted for groups underrepresented in this study, such as those with very low CrCl, a low BMI, or receiving renal replacement therapy. This algorithm should be validated in other centers for patients with thermal injuries.

The levels of vancomycin in the blood and the wound after the local treatment of bone and soft-tissue infection with antibiotic-loaded calcium sulphate as carrier material

AIMS

Calcium sulphate (CaSO₄) is a resorbable material that can be used simultaneously as filler of a dead space and as a carrier for the local application of antibiotics. Our aim was to describe the systemic exposure and the wound fluid concentrations of vancomycin in patients treated with vancomycin-loaded CaSO₄ as an adjunct to the routine therapy of bone and joint infections.

PATIENTS AND METHODS

A total of 680 post-operative blood and 233 wound fluid samples were available for analysis from 94 implantations performed in 87 patients for various infective indications. Up to 6 g of vancomycin were used. Non-compartmental pharmacokinetic analysis was performed on the data from 37 patients treated for an infection of the hip.

RESULTS

The overall systemic exposure remained within a safe range, even in patients with post-operative renal failure, none requiring removal of the pellets. Local concentrations were approximately ten times higher than with polymethylmethacrylate (PMMA) as a carrier, but remained below reported cell toxicity thresholds. Decreasing concentrations in wound fluid were observed over several weeks, but remained above the common minimum inhibitory concentrations for Staphylococcus up to three months post-operatively.

CONCLUSION

This study provides the first pharmacokinetic description of the local application of vancomycin with CaSO₄ as a carrier, documenting slow release, systemic safety and a release profile far more interesting than from PMMA. In particular, considering in vitro data, concentrations of vancomycin active against staphylococcal biofilm were seen for several weeks. Cite this article: Bone Joint J 2017;99-B:1537-44.

Characterization of variables for potential impact on vancomycin pharmacokinetics in thermal or inhalation injury

OBJECTIVE

To characterize the pharmacokinetics of vancomycin dosing in thermal or inhalation injury as they relate to percent total body surface area burn (TBSA) and days since injury (DSI).

METHODS

This retrospective 3-year study included patients with thermal or inhalation injury receiving vancomycin. Patient demographics and course data were collected using the institution's electronic medical record.

RESULTS

Six hundred and fifty-four patients were included in the study; 124 remained after exclusion. Clearance (CL) was augmented in patients closer to their date of injury. CL and total daily dose requirements significantly increased with larger percent TBSA injured that was independent of volume of distribution (Vd). Larger percent TBSA also predicted increased occurrence of renal injury prior to vancomycin initiation. A modified sample set was also analyzed to control for renal dysfunction. Creatinine clearance (CrCl) estimated via the Cockcroft-Gault equation significantly impacted CL and total daily dose. To obtain a goal trough of 15-20mg/L, the average patient in the modified sample with ≥10% TBSA required 64.7mg/kg/day (or 16.2mg/kg every 6hours).

CONCLUSIONS

DSI, percent TBSA, and CrCl can be used to predict faster vancomycin CL and need for higher total daily doses. Augmented pharmacokinetics can occur as early as two days after injury and decrease with time. Acceptable target trough attainment is still lacking and this data should assist in performance improvements for initial vancomycin dosing.

The safety and efficacy of high versus low vancomycin trough levels in the treatment of patients with infections caused by methicillin-resistant Staphylococcus aureus: a meta-analysis

BACKGROUND

Recent guidelines have recommended vancomycin trough levels of 15-20 mg/L for treatment of serious infections caused by methicillin-resistant Staphylococcus aureus (MRSA). However, high trough levels may increase risk of nephrotoxicity and mortality, and high vancomycin trough levels have not been well studied. This study was designed to combine safety and efficacy results from independent studies and to compare between high and low vancomycin trough levels in the treatment of MRSA-infected patients using meta-analysis.

METHODS

From 19 eligible studies, 9 studies were included in meta-analysis to compare clinical success between high and low vancomycin trough levels, while 10 and 11 studies met criteria for comparing trough levels and nephrotoxicity and trough levels and mortality, respectively. The PubMed/Medline, Web of Science, and Scopus databases, and hand searching were used to identify eligible studies dated up to March 2016. Of 2344 subjects with MRSA infection, 1036 were assigned to trough levels ≥15 mg/L and 1308 to trough levels <15 mg/L.

RESULTS

High vancomycin trough levels were found to be associated with risk of nephrotoxicity (odds ratio [OR] 2.14, 95 % confidence interval [CI] 1.42-3.23 and adjusted OR 3.33, 95 % CI 1.91-5.79). There was no evidence of difference between high and low vancomycin trough levels for mortality (OR; 1.09; 95 % CI 0.75-1.60) or clinical success (OR 1.07; 95 % CI 0.68-1.68).

CONCLUSION

In this study, high vancomycin trough levels were identified as an independent factor associated with risk of nephrotoxicity in MRSA-infected patients. Association between vancomycin trough levels and both adverse effects and clinical outcomes requires further study.

Vancomycin dosing nomograms targeting high serum trough levels in different populations: pros and cons

PURPOSE

Utilization of higher doses of vancomycin to achieve the trough concentrations of 15-20 mg/L for complicated infections has been recommended by the Infectious Diseases Society of America clinical practice guideline in recent years. Concerning this recommendation, several nomograms have been constructed targeting this optimal trough level range in different populations of patients. In this review, we have collected available nomograms targeting high trough serum levels of vancomycin, particularly comparing their advantages and limitations.

METHOD

The data were collected by searching Scopus, PubMed, Google scholar, Medline, and Cochrane database systematic reviews. The key words used as search terms were "vancomycin", "high trough level", "dosing nomogram", "dosing strategy", "neonates", "critically ill", "pediatrics", and "hemodialysis". We have included 17 related human studies published up to the date of this publication.

RESULTS & CONCLUSION

Most of the available nomograms have determined the doses according to body weight and renal function. Their initial predicting success rate were 44-76 % for non-critically ill patients, 42-84 % for critically ill patients, 54 % for one nomogram specially designed for hemodialysis patients, and 71 % for the only nomogram developed for neonates. Based on validation studies, in most of cases, using a vancomycin dosing nomogram significantly improved and accelerated achievement of target trough concentrations. However, it should be noted that there are limited data about patients' clinical and microbiological outcomes and they are only validated in narrow groups of patients. Thus, their widespread application could not be encouraged for all patients before performing adequately powered, prospective randomized studies.

Identification of risk factors for nephrotoxicity in patients receiving extended-duration, high-trough vancomycin therapy

BACKGROUND

In the past, impurities in vancomycin formulations were thought to contribute to nephrotoxicity. In contrast, when current, purer formulations are dosed at conventional trough levels (i.e., 5-15 mg/L), the incidence of nephrotoxicity is relatively low. Recent guidelines have recommended targeting higher vancomycin trough levels in treatment of complicated methicillin-resistant Staphylococcus aureus infections. Dosing based on these higher trough levels may be associated with nephrotoxicity, so the potential risk factors for vancomycin-associated nephrotoxicity require clearer definition.

OBJECTIVES

To determine the occurrence of nephrotoxicity in patients receiving more than 7 days of vancomycin therapy with high trough levels (15-20 mg/L) and to identify and evaluate specific risk factors related to development of vancomycin-associated nephrotoxicity (i.e., serum creatinine ≥ 44.2 μmol/L or increase ≥ 50% [i.e., ≥ 26.2 μmol/L] from baseline on 2 consecutive days).

METHODS

Health care records were reviewed for patients seen at 2 major teaching hospitals between January 2008 and March 2011. Patients who had attained high trough levels of vancomycin were screened for eligibility. Patients with unstable renal function, those undergoing hemodialysis, and those for whom dosage and/or sampling times were unclear were excluded. Univariate and multivariate analyses were performed to identify risk factors associated with nephrotoxicity. Univariate variables with p < 0.1 were included in the logistic regression model.

RESULTS

Of the 176 patients with high trough levels included in the analysis, 24 (14%) experienced nephrotoxicity. In univariate analysis, admission to a general medicine unit (the setting of care for 16 [67%] of the 24 patients with nephrotoxicity) and extended duration of vancomycin treatment were identified as risk factors for nephrotoxicity (p < 0.1). Other risk factors included gastrointestinal comorbidity (p = 0.056), malignancy (p = 0.044), and febrile neutropenia (p = 0.032). Multivariate analysis identified treatment on general medicine units and treatment courses longer than 7 days as independent predictors of vancomycin-associated nephrotoxicity.

CONCLUSION

Patients being treated on general medicine units and those receiving vancomycin for more than 7 days had an increased likelihood of experiencing nephrotoxicity. The increased risk for patients on general medicine units is likely multifactorial. The relationship between treatment duration and risk of nephrotoxicity appeared to be linear. When using extended-duration, high-trough vancomycin therapy, clinicians should be vigilant in monitoring for nephrotoxicity.

Retrospective review of vancomycin-induced nephrotoxicity in patients with leukemia

Background

The occurrence of nephrotoxicity with vancomycin is approximately 17%, but can increase to 35% when combined with other nephrotoxic agents. Patients with hematologic malignancies may be at greater risk for vancomycin-induced nephrotoxicity due to nephrotoxic chemotherapy and tumor lysis syndrome.

Objective

The primary objective of this study was to determine the occurrence of nephrotoxicity in adult patients with leukemia receiving vancomycin.

Methods

A retrospective review approved by the Institutional Review Board was conducted on adult patients with leukemia who received at least one dose of vancomycin during hospital admission between 1 January 2009 and 30 April 2009.

Results

Forty patients had an occurrence of nephrotoxicity (16%) while 210 patients did not have an occurrence of nephrotoxicity. In multivariate analysis, variables significantly associated with development of nephrotoxicity included active disease status (odds ratio, 4.38 [95% CI 1.1–29.4], p = 0.0291), concomitant intravenous acyclovir administration (odds ratio, 3.83 [95% CI, 1.6–8.9]; p = 0.0022), and concomitant amphotericin administration (odds ratio, 4.26 [95% CI, 1.9–9.4]; p = 0.0004).

Conclusion

The occurrence of nephrotoxicity in patients with leukemia treated with vancomycin was 16% in our study, similar to previously published reports. Active disease status and concomitant use of intravenous acyclovir and amphotericin were identified as significant risk factors for development of nephrotoxicity. The presence of risk factors for vancomycin nephrotoxicity should be evaluated prior to initiation of therapy to determine appropriateness of use.