Outcome assessment of minimizing vancomycin monitoring and dosing adjustments

Continued professional development: A comparison of online vs. in-person workshops

INTRODUCTION

Pharmacy practice continues to change and therefore requires lifelong health professions education. These practice changes require academics and leaders in pharmacy to identify how to best teach and train pharmacists to manage patient care services. This study assessed whether an online training module is as effective as an in-person workshop to train pharmacists to apply dosing and therapeutic monitoring of vancomycin.

METHODS

The primary endpoint measured the difference in average assessment score change between pre- and post-training between intervention groups. All pharmacists completed: (1) a baseline pretest, (2) Session 1 online, (3) Session 2 (an online training module or in-person workshop), (4) a posttest, and (5) a voluntary survey of perceptions on training.

RESULTS

A total of 56 pharmacists completed the training, 43% online and 57% in-person. The multiple linear regression included pretest, training method, and pharmacists' role on posttest (R² = 0.1041 and P = .34). A voluntary anonymous survey about perceptions on the training was completed by 20 participants. On average, perceptions were agreeable on an eight-item Likert scale between groups (Cronbach's alpha = 0.77). The total scores for the Likert scale were 27 ± 3.3 vs. 23 ± 1.6, P = .001, in the online and in-person sessions, respectively. More participants in the online group agreed that they had enough time to comprehend and apply the material, 4 vs. 3 (on the Likert scale).

CONCLUSIONS

An online training module is as effective as an in-person workshop at training pharmacists to apply vancomycin dosing and monitoring.

Relationship Status between Vancomycin Loading Dose and Treatment Failure in Patients with MRSA Bacteremia: It's Complicated

INTRODUCTION

A one-time vancomycin loading dose of 25-30 mg/kg is recommended in the current iteration of the vancomycin consensus guidelines in order to more rapidly achieve target serum concentrations and hasten clinical improvement. However, there are few clinical data to support this practice, and the extents of its benefits are largely unknown.

METHODS

A multicenter, retrospective, cohort study was performed to assess the impact of a vancomycin loading dose (≥ 20 mg/kg) on clinical outcomes and rates of nephrotoxicity in patients with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. The study matched patients in a 1:1 fashion based on age, Pitt bacteremia score, and bacteremia source. The primary outcome was composite treatment failure (30-day mortality, bacteremia duration ≥ 7 days after vancomycin initiation, persistent signs and symptoms of infection ≥ 7 days after vancomycin initiation, or switch to an alternative antimicrobial agent). Secondary outcomes included duration of bacteremia, length of stay post-bacteremia onset, and nephrotoxicity.

RESULTS

A total of 316 patients with MRSA bacteremia were included. Median first doses in the loading dose and non-loading dose groups were 23.0 mg/kg and 14.3 mg/kg, respectively (P < 0.001). No difference was found in composite failure rates between the non-loading dose and loading dose groups (40.5% vs. 36.7%; P = 0.488) or in the incidence of nephrotoxicity (12.7% vs. 16.5%; P = 0.347). While multivariable regression modeling showed receipt of a vancomycin loading dose on a mg/kg basis was not significantly associated with composite failure [aOR 0.612, 95% CI (0.368-1.019)]; post hoc analyses demonstrated that initial doses ≥ 1750 mg were independently protective against failure [aOR 0.506, 95% CI (0.284-0.902)] without increasing the risk for nephrotoxicity [aOR 0.909, 95% CI (0.432-1.911)].

CONCLUSION

These findings suggest that initial vancomycin doses above a certain threshold may decrease clinical failures without increasing toxicity and that weight-based dosing might not be the optimal strategy.

Hospitalized Patients With and Without Hemodialysis Have Markedly Different Vancomycin Pharmacokinetics: A Population Pharmacokinetic Model-Based Analysis

BACKGROUND

Despite being in clinical use for about 6 decades, vancomycin dosing remains perplexing and complex.

METHODS

A population pharmacokinetic modeling and simulation approach was used to evaluate the efficiency of the current nomogram-based dosing of vancomycin. Serum vancomycin concentrations were obtained as a part of routine therapeutic drug monitoring from two 500-bed academic medical centers. A population pharmacokinetic model was first built using these therapeutic drug monitoring data. Population pharmacokinetic modeling was conducted using NONMEM (7.2 and 7.3). The forward addition-backward elimination approach was used to test the covariate effects. Appropriate numerical and visual criteria were used as model diagnostics for checking model appropriateness and model qualification. The current nomogram efficiency was evaluated by determining the percentage of subjects in the therapeutic range (10-20 mg/L).

RESULTS

A 2-compartment model with between-subject variability on clearance (CL), central volume of distribution (Vc), and peripheral volume of distribution best fit the data. Blood urea nitrogen, age, creatinine clearance, and hemodialysis status were significant covariates on clearance. Hemodialysis status was a significant covariate on Vc and peripheral volume of distribution. In the final model, creatinine clearance was retained as a covariate on CL whereas hemodialysis status was retained as covariate on both CL and Vc. Using Monte Carlo simulations, the current nomogram was optimized by the addition of a loading dose and reducing the maintenance doses. The current nomogram is suboptimal. Optimization of the nomogram resulted in >40% subjects consistently being in the therapeutic range at troughs collected after the first 6 doses.

CONCLUSIONS

CL and Vc differ markedly between patients undergoing hemodialysis and those not undergoing hemodialysis. Dosing nomogram based on these covariate relationships may potentially help in accurate dosing of vancomycin.

Vancomycin Dosing and Monitoring: Critical Evaluation of the Current Practice

After more than six decades of its use as the mainstay antibiotic for the treatment of multidrug-resistant Gram-positive bacterial infections, dosing and monitoring of vancomycin therapy have not been optimized. The current vancomycin therapeutic guidelines recommend empiric doses of 15-20 mg/kg administered by intermittent infusion every 8-12 h in patients with normal kidney function. Additionally, the guidelines recommend trough concentration of 15-20 mg/L as a therapeutic goal for adult patients with severe infections. This review critically discusses the current guidelines considering the basic pharmacokinetics and pharmacodynamics of vancomycin and the recent published reports from clinical studies. More in-depth discussion will be focused on (1) providing evidence of advantages of administering vancomycin by continuous infusion compared to intermittent infusion; (2) revising the current practice of trough-only monitoring versus the area under concentration-time curve (AUC); and (3) assessing the current practice of weight-based dosing versus AUC-based dosing. Using the gathered information presented in this paper, two user-friendly and scientifically based dosing strategies are proposed to improve the efficiency of vancomycin dosing while avoiding the risk of nephrotoxicity and minimizing the cost of therapeutic drug monitoring.

Attenuation of antimicrobial activity by the human steroid hormones

Upon entering the human host, Staphylococcus aureus is exposed to endogenous steroid hormones. The interaction between S. aureus and dehydroepiandosterone (DHEA) results in an increased resistance to the host cationic defense peptide, β-1 defensin, as well as vancomycin and other antibiotics that have a positive charge. The increased resistance to vancomycin is phenotypic and appears to correlate with a DHEA-mediated alteration in cell surface architecture. DHEA-mediated cell surface changes include alterations in: cell surface charge, surface hydrophobicity, capsule production, and carotenoid production. In addition, exposure to DHEA results in decreased resistance to lysis by Triton X-100 and lysozyme, indicating activation of murien hydrolase activity. We propose that DHEA is an interspecies quorum-like signal that triggers innate phenotypic host survival strategies in S. aureus that include increased carotenoid production and increased vancomycin resistance. Furthermore, this DHEA-mediated survival system may share the cholesterol-squalene pathway shown to be statin sensitive thus, providing a potential pathway for drug targeting.

Antimicrobial Stewardship Approaches in the Intensive Care Unit

Antimicrobial stewardship programs aim to monitor, improve, and measure responsible antibiotic use. The intensive care unit (ICU), with its critically ill patients and prevalence of multiple drug-resistant pathogens, presents unique challenges. This article reviews approaches to stewardship with application to the ICU, including the value of diagnostics, principles of empirical and definitive therapy, and measures of effectiveness. There is good evidence that antimicrobial stewardship results in more appropriate antimicrobial use, shorter therapy durations, and lower resistance rates. Data demonstrating hard clinical outcomes, such as adverse events and mortality, are more limited but encouraging; further studies are needed.

Acute Kidney Injury Associated With Vancomycin When Laxity Leads to Injury and Findings on Kidney Biopsy

The issue of vancomycin-induced acute kidney injury (AKI) has resurged with the use of intravenous vancomycin as a first-line antibiotic, often for prolonged periods of time for the management of serious methicillin-resistant Staphylococcus aureus infections, and with a higher recommended trough level (15-20 μg/mL). We have observed 3 patients on intravenous vancomycin who developed very high trough levels (>40 μg/mL) and severe (stage 3) AKI. Those 3 patients underwent kidney biopsy for unresolving AKI, which revealed findings compatible with acute tubular necrosis. The first patient initially developed asymptomatic acute interstitial nephritis because of a concomitant antibiotic that caused worsening of kidney function, and the dose of vancomycin was not properly adjusted while staying at the nursing home. The second was an emaciated patient (BMI, 14) whose serum creatinine level was a deceptive marker of kidney function for the proper dosing of vancomycin, resulting in a toxic level. The third patient developed vancomycin-related AKI on an initially high therapeutic level, which then contributed to further rising in vancomycin level and subsequently causing severe AKI. One patient required hemodialysis, but all 3 patients ultimately recovered their kidney function significantly. A regular monitoring (preferably twice weekly) of serum creatinine and vancomycin trough level is advisable to minimize vancomycin-associated AKI, primarily acute tubular necrosis, for patients requiring prolonged administration of vancomycin (>2 weeks) on the currently recommended higher therapeutic trough levels (>15 μg/mL).

Infectious Diseases: Pharmacologic Treatment Options for Nosocomial Pneumonia Involving Methicillin-Resistant Staphylococcus aureus

Objective:

To discuss current and potential treatment options for nosocomial pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA).

Data Sources:

A MEDLINE search (1966–January 2007) was conducted to identify English-language literature on pharmacotherapy of nosocomial pneumonia and the bibliographies of pertinent articles. Programs and abstracts from infectious disease meetings were also searched. Search terms included MRSA, nosocomial pneumonia, pulmonary infections, vancomycin, quinupristin/dalfopristin, linezolid, daptomycin, tigecycline, dalbavancin, oritavancin, and ceftobiprole.

Data Selection and Data Extraction:

All articles were critically evaluated and all pertinent information was included in this review.

Data Synthesis:

Vancomycin has been the drug of choice for MRSA infections for many years. Recent data suggest that linezolid may be superior to vancomycin in the treatment of MRSA nosocomial pneumonia. However, there are limitations to the available data. Therefore, prospective, randomized studies are needed before linezolid is recommended as the preferred first-line therapy. Other approved agents for nosocomial MRSA infections, such as quinupristin/dalfopristin and daptomycin, should not be used in the treatment of MRSA pneumonia, as they were inferior in clinical trials. Tigecycline has excellent activity against MRSA in vitro, but should not be routinely used for the treatment of MRSA pneumonia, as clinical data are lacking. In a Phase III clinical trial, an anti-MRSA cephalosporin, ceftobiprole, is being evaluated for effectiveness against nosocomial pneumonia. Investigational glycopeptides may eventually have a role in the treatment of nosocomial pneumonia, but data are currently lacking.

Conclusions:

Vancomycin is still the drug of choice for treatment of MRSA pneumonia, and linezolid should be used as an alternative agent. Linezolid should carry strong consideration for patients with vancomycin-induced nephrotoxicity or a documented lack of response to vancomycin. Tigecycline and investigational agents with activity against MRSA may be future options for nosocomial pneumonia due to MRSA.

Pharmacist and Physician Collaborative Practice Model Improves Vancomycin Dosing in an Intensive Care Unit

Objective:

A pharmacist and physician collaborative practice intervention to improve the initial dosing of vancomycin was implemented with the goal of decreasing the number of subtherapeutic first troughs and increasing the number of therapeutic troughs.

Methods:

Using the best available evidence, a nomogram was created to determine the initial vancomycin dose. The nomogram utilized actual bodyweight and glomerular filtration rate (eGFR) estimated with the MDRD4 equation. The dose was based on the 2009 ASHP/IDSA/SIDP guidelines, which recommended 15–20 mg/kg every 8–12 hours. Providers ordered “vancomycin IV dosed per pharmacy”.

Results:

The pre- (n = 75) and post-intervention (n = 108) cohorts had similar age, gender distribution, weight, and eGFR. The median total daily vancomycin dose was similar in pre- and post-intervention groups (2000 mg), although the median first trough was higher following the intervention (13.0 vs. 14.8 mcg/ml, p = 0.03). Following the intervention, the proportion of first troughs under 10 mcg/ml decreased (32% to 13%, p = 0.003), while the proportion of troughs in the 10 – 20 mcg/ml therapeutic range increased (50.7% vs. 69.4%, p= 0.01). There was no difference in the proportion of troughs over 20 mcg/ml (17.3% vs. 17.6%, p= 0.96).

Conclusions:

A multi-disciplinary intervention utilizing a nomogram-based pharmacy collaborative practice model significantly improves the proportion of therapeutic initial vancomycin troughs and decreases the number of subtherapeutic troughs by half.

Clinical Application and Evaluation of Vancomycin Dosing in Adults

Objective:

To evaluate the accuracy of a vancomycin dosing method (study method) in estimating volume of distribution (Vd) and clearance of vancomycin (Clvanco) and the frequency with which it would provide serum vancomycin concentrations (SVCs) within a specified range compared with other published methods.

Methods:

One hundred and seven patients with 108 pairs of SVCs were used to calculate patient-specific Vd and Clvanco. Based on these patient-specific Vd and Clvanco values, the predictive ability of the estimated parameters from the study dosing method (Vd [L] = 0.17 [age] + 0.22 [actual body weight] + 15; Clvanco = creatinine clearance) was evaluated against three previously published pharmacokinetic dosing methods, using predictive performance analysis (precision and bias). Furthermore, the patient-specific pharmacokinetic parameters were used to simulate steady-state peak and trough SVCs, using first-order pharmacokinetic equations from doses derived from the study method, the three different pharmacokinetic methods, and two other published dosing schemes. The frequency with which each method would have achieved target peak and trough SVCs was determined.

Results:

The study method was found to be more precise and less biased (p < 0.05) than comparative methods in predicting vancomycin Vd and Clvanco. The study method also resulted in a higher frequency of steady-state peak and trough SVCs within the target range specified.

Conclusions:

The study method presented here provided a reliable estimation of vancomycin pharmacokinetic parameters that was easily applied to various patient populations to individualize vancomycin dosing, and frequently yielded SVCs within a predictable and desired range.

Implementing an Antibiotic Stewardship Program: Guidelines by the Infectious Diseases Society of America and the Society for Healthcare Epidemiology of America

Evidence-based guidelines for implementation and measurement of antibiotic stewardship interventions in inpatient populations including long-term care were prepared by a multidisciplinary expert panel of the Infectious Diseases Society of America and the Society for Healthcare Epidemiology of America. The panel included clinicians and investigators representing internal medicine, emergency medicine, microbiology, critical care, surgery, epidemiology, pharmacy, and adult and pediatric infectious diseases specialties. These recommendations address the best approaches for antibiotic stewardship programs to influence the optimal use of antibiotics.

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.

An open-label, pragmatic, randomized controlled clinical trial to evaluate the comparative effectiveness of daptomycin versus vancomycin for the treatment of complicated skin and skin structure infection

Background

Treatment of complicated skin and skin structure infection (cSSSI) places a tremendous burden on the health care system. Understanding relative resource utilization associated with different antimicrobials is important for decision making by patients, health care providers, and payers.

Methods

The authors conducted an open-label, pragmatic, randomized (1:1) clinical study (N = 250) to compare the effectiveness of daptomycin with that of vancomycin for treatment of patients hospitalized with cSSSI caused by suspected or documented methicillin-resistant Staphylococcus aureus infection. The primary study end point was infection-related length of stay (IRLOS). Secondary end points included health care resource utilization, cost, clinical response, and patient-reported outcomes. Patient assessments were performed daily until the end of antibiotic therapy or until hospital discharge, and at 14 days and 30 days after discharge.

Results

No difference was found for IRLOS, total LOS, and total inpatient cost between cohorts. Hospital LOS contributed 85.9 % to the total hospitalization cost, compared with 6.4 % for drug costs. Daptomycin showed a nonsignificant trend toward a higher clinical success rate, compared with vancomycin, at treatment days 2 and 3. In the multivariate analyses, vancomycin was associated with a lower likelihood of day 2 clinical success (odds ratio [OR] = 0.498, 95 % confidence interval [CI], 0.249–0.997; P < 0.05).

Conclusion

This study did not provide conclusive evidence of the superiority of one treatment over the other in terms of clinical, economic, or patient outcomes. The data suggest that physician and patient preference, rather than drug acquisition cost, should be the primary driver of initial antibiotic selection for hospitalized patients with cSSSI.

Trial registration

ClinicalTrials.gov: NCT01419184 (Date: August 16, 2011)

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1261-9) contains supplementary material, which is available to authorized users.

Population pharmacokinetics of vancomycin in adult Chinese patients with post-craniotomy meningitis and its application in individualised dosage regimens

PURPOSE

Vancomycin (VCM) is a first-line antibacterial drug used to treat post-craniotomy meningitis (PCM). VCM pharmacokinetic parameters are altered in PCM patients, compared to those in other patients. Although VCM population pharmacokinetics (PPK) has been reported, changes in VCM PPK in adult Chinese PCM patients remain unknown. We developed a VCM PPK model in adult Chinese PCM patients and proposed a new strategy for individualising VCM administration using this model.

METHODS

Data was obtained from a prospective study of 100 adult PCM patients in the Neurosurgery Department of the First Affiliated Hospital of Fujian Medical University. The trough concentrations at steady state were determined by enzyme multiplied immunoassay. Nonlinear mixed-effect model software was employed to develop the PPK model. The final model was evaluated using the bootstrap method and normalised prediction error distribution and through the testing of 20 independent adult PCM patients.

RESULTS

VCM clearance in PCM patients was higher than that observed in other patients. Creatinine clearance affected VCM clearance, whereas no co-administered drugs influenced VCM pharmacokinetics. Trough concentrations were accurately predicted by the final model, while the prediction errors were less than ±32 %. Moreover, a new strategy for individualising VCM regimens using the PPK model was proposed and validated.

CONCLUSIONS

A PPK model was developed to estimate the individual clearance in inpatients receiving intravenously infused VCM and could be used to develop individualised dosing of adult Chinese PCM patients.

Evaluation of a Pharmacist-Directed Vancomycin Dosing and Monitoring Pilot Program at a Tertiary Academic Medical Center

BACKGROUND

Consensus guidelines recommend vancomycin doses of 15 to 20 mg/kg every 8 to 12 hours in patients with normal renal function.

OBJECTIVE

To evaluate the effect of a pharmacist-directed vancomycin dosing and monitoring pilot program on the percentage of patients receiving targeted weight-based dosing recommendations.

METHODS

This was a pre-/postevaluation study, approved by the institutional review board at our institution, comparing retrospectively reviewed vancomycin dosing practices hospital-wide between September 1 and September 30, 2010 to patients prospectively managed by a pharmacist-directed vancomycin pilot program between February 1 and April 26, 2011. All adult inpatients receiving intravenous vancomycin were included, unless patients had a creatinine clearance less than or equal to 60 mL/min or indication for therapy was surgical prophylaxis or febrile neutropenia. The primary outcome was the percentage of patients who received optimal vancomycin dosing defined as ≥30 mg/kg/d within 24 hours of initiation of therapy. Secondary outcomes included number of pharmacist interventions, length of therapy and incidence of nephrotoxicity while receiving vancomycin.

RESULTS

A total of 319 patients were analyzed, 161 preimplementation and 158 postimplementation. The percentage of patients who received optimal vancomycin dosing was significantly higher postimplementation of the pilot program, 96.8 versus 40.4% (P < 0.001). Pharmacist-directed interventions postimplementation, resulted in 50% more patients being dosed optimally (P < 0.001). Patients in the pilot program also had a shorter length of therapy (10.0 vs 8.4 days, P < 0.003) and a lower incidence of nephrotoxicity (8.7% vs 3.2%, P = 0.006).

CONCLUSIONS

This pharmacist-directed vancomycin pilot program significantly increased the percentage of patients optimally dosed according to consensus guidelines within 24 hours of initiation of therapy.

Prophylactic antibiotic administration for post cardiothoracic surgery sternal wounds: a retrospective study

BACKGROUND

Cardiothoracic surgery sternal infections are difficult to treat situations. Until now there are no clear guidelines which or if an antibiotic could be used as prophylactic treatment.

PATIENTS AND METHODS

We collected retrospectively data from 535 patients from our hospital which underwent cardiothoracic surgery and recorded several biological parameters and technical aspects of the surgery.

RESULTS

It was observed that patients to whom vancomycin was administered had less post surgery infection than those to whom begalin was administered. Male who were treated with vancomycin it was observed that they had 1.67 chances to be treated properly than female. Patients which were hospitalized for more than 7 days before surgery had 62.6% higher chances for post surgery infection.

CONCLUSIONS

It was observed that vancomycin can be used as a prophylactic treatment for cardiothoracic surgeries acting efficiently against sternal wounds.

Evaluation of Treatment Courses When Vancomycin Is Given Every 8 Hours in Adult Patients

BACKGROUND

Several nomograms include recommendations to give intravenous (IV) vancomycin at 8-hour dosing intervals (Q8H). However, there is a lack of detailed data regarding this dosing recommendation.

METHODS

A retrospective chart review of 100 patients who received 107 treatment courses of vancomycin Q8H for at least 5 days was performed. Distribution of vancomycin trough levels and rate of nephrotoxicity were evaluated.

RESULTS

Median patient age was 38 years (interquartile range [IQR] 27-50 years), median weight was 67 kg (IQR 55-79 kg), and median creatinine clearance was 124 mL/min (IQR 101-147 mL/min). Median duration of Q8H dosing was 9 days (IQR 7-12 days). Within the initial 96 hours, only 7% (7 of 104) of maximum trough concentrations were >20 mg/L (median dose 15 mg/kg [IQR 15-18 mg/kg]). After 96 hours of Q8H dosing, 34% (30 of 89) of maximum troughs were >20 mg/L (median dose 17 mg/kg [IQR 15-20 mg/kg]), P = .0005. The rate of nephrotoxicity was 4%.

CONCLUSION

We observed an increase in the percentage of trough levels >20 mg/L later during treatment courses of vancomycin IV Q8H with a relatively small corresponding increase in vancomycin dose. Close monitoring of trough levels (eg, every 3 days) with prolonged courses of vancomycin IV Q8H is warranted.

Underestimation of the calculated area under the concentration-time curve based on serum creatinine for vancomycin dosing

Background

The ratio of the steady-state 24-hour area under the concentration-time curve (ssAUC₂₄) to the MIC (AUC₂₄/MIC) for vancomycin has been recommended as the preferred pharmacodynamic index. The aim of this study was to assess whether the calculated AUC₂₄ (cAUC₂₄) using the creatinine clearance (CLcr) differs from the ssAUC₂₄ based on the individual pharmacokinetic data estimated by a commercial software.

Materials and Methods

The cAUC₂₄ was compared with the ssAUC₂₄ with respect to age, body mass index, and trough concentration of vancomycin and the results were expressed as median and interquartile ranges. A correlation between the cAUC₂₄ and ssAUC₂₄ and the trough concentration of vancomycin was evaluated. The probability of reaching an AUC₂₄/MIC of 400 or higher was compared between the cAUC₂₄ and ssAUC₂₄ for different MICs of vancomycin and different daily doses by simulation in a subgroup with a trough concentration of 10 mg/L and higher.

Results

The cAUC₂₄ was significantly lower than the ssAUC₂₄ (392.38 vs. 418.32 mg·hr/L, P < 0.0001) and correlated weakly with the trough concentration (r = 0.649 vs. r = 0.964). Assuming a MIC of 1.0 mg/L, the probability of reaching the value of 400 or higher was 77.5% for the cAUC₂₄/MIC and 100% for the ssAUC₂₄/MIC in patients with a trough concentration of 10 mg/L and higher. If the MIC increased to 2.0 mg/L, the probability was 57.7% for the cAUC₂₄/MIC and 71.8% for the ssAUC₂₄/MIC at a daily vancomycin dose of 4,000 mg.

Conclusions

The cAUC₂₄ using the calculated CLcr is usually underestimated compared with the ssAUC₂₄ based on individual pharmacokinetic data. Therefore, to obtain a more accurate AUC₂₄, therapeutic monitoring of vancomycin rather than a simple calculation based on the CLcr should be performed, and a more accurate biomarker for renal function is needed.

Influence of pharmacokinetics/pharmacodynamics of antibacterials in their dosing regimen selection

The choice of antimicrobial dosing in clinical practice in the past was based upon a 'penicillin mentality', that is, on the assumption that the in vivo antimicrobial efficacy is dependent on the duration of drug levels above the minimum inhibitory concentration of target microorganisms. Really, a rational antimicrobial therapy is strongly related to a basic understanding of the influence the patient has on the antibiotic (pharmacokinetics [PKs]) and the patient's response to the specific drug effects (pharmacodynamics [PDs]). PK/PD parameters are essential in facilitating the translation of microbiological activity into clinical situations, ensuring a successful outcome. This review will analyze the typical patterns of antimicrobial activity and the corresponding PK/PD parameters, with a special focus on a PK/PD dosing approach with the most commonly utilized antimicrobial agent classes.

Evaluation of Vancomycin Dosing and Monitoring in Adult Medicine Patients

Purpose

To assess the clinical impact of a vancomycin dosing protocol and monitoring tool on initial dose, dosing interval, and trough concentrations in adult medicine patients.

Methods

This was a retrospective chart review of adult medicine patients who received at least one dose of vancomycin and were admitted during the pre-implementation period, February 1 to April 2009, or during the post-implementation period, June 1 to October 31, 2009. All outcomes for patients in the pre-implementation group were compared to those in the post-implementation group. The primary outcomes were frequency of appropriate initial vancomycin dose and dosing interval. The secondary outcomes included frequency of appropriate initial vancomycin trough concentrations, mean number of levels drawn per patient, and mean duration of therapy.

Results

A total of 450 patients were identified, with 225 patients in each study group. Patients with an appropriate initial vancomycin dose significantly increased in the post-implementation group (56% vs 40%; P < .001). The number of patients with an appropriate original dosing interval (67% vs 63%; P = 0.32), appropriate initial trough concentration (44% vs 45%; P = 0.89), mean number of levels drawn (1.9 vs 2.1; P = 0.56), and duration of therapy (4.9 vs 5.0; P = 0.77) was similar between the 2 groups.

Conclusions

The implementation of a vancomycin empiric dosing protocol and monitoring tool had a significant impact on the initial dose. Further education regarding vancomycin dosing and monitoring is warranted to improve initial dosing interval, initial trough concentration, number of levels drawn, and duration of therapy.

Daptomycin versus vancomycin for bloodstream infections due to methicillin-resistant Staphylococcus aureus with a high vancomycin minimum inhibitory concentration: a case-control study

BACKGROUND

Reports have found a link between vancomycin treatment failure in methicillin-resistant Staphyloccocus aureus (MRSA) bloodstream infections (BSIs) and higher vancomycin minimum inhibitory concentrations (MICs), despite MICs being below the susceptibility breakpoint of 2 μg/mL. Consensus guidelines recommend considering use of alternative agents for infections involving a higher vancomycin MIC, despite few data to support this approach.

METHODS

This retrospective case-control study evaluated the effectiveness and safety of vancomycin, compared with that of daptomycin, in the treatment of MRSA BSIs with a high vancomycin MIC (ie, >1 μg/mL).

RESULTS

A total of 118 vancomycin-treated subjects were compared with 59 daptomycin-treated subjects. Clinical failure, defined compositely as mortality, microbiologic failure, and/or recurrence of infection, was numerically lower in daptomycin-treated subjects (31% vs 17%; P = .084) and was mainly driven by a lower incidence of mortality in the daptomycin group (20% vs 9%; P = .046). Factors independently associated with clinical failure included acute renal failure (odds ratio [OR], 3.91 [95% confidence interval {CI}, 1.05-14.56]) and vancomycin treatment group (OR, 3.13 [95%, CI, 1.00-9.76]). Right-sided endocarditis was independently associated with clinical success (OR, 0.07 [95% CI, .01-.83]). A comparison of 60-day mortality between vancomycin- and daptomycin-treated subjects found a higher probability of survival in the daptomycin-treated group (P = .022).

CONCLUSIONS

The results demonstrated that daptomycin was associated with a better outcome compared with vancomycin for the treatment of BSIs due to MRSA with higher vancomycin MICs. These findings support the recommendations of recent guidelines, which suggest consideration of the switch to alternative agents when the isolate has a high vancomycin MIC or when patients are not improving during receipt of therapy.

Traditional weight-based vancomycin dosing is inadequate in critically ill trauma patients

PURPOSE

Our aim was to evaluate our institution's compliance with weight-based vancomycin dosing recommendations for pneumonia in critically ill injured patients and to assess the success rate in achieving therapeutic serum vancomycin levels. Additionally, we sought to assess the incidence of vancomycin-induced nephrotoxicity.

METHODS

All injured intensive care unit (ICU) patients receiving intravenous vancomycin between May 1, 2004 and July 31, 2010 were identified through our trauma database and pharmacy records. The initial weight-based dose was calculated and compared with vancomycin trough levels.

RESULTS

Thirty patients were identified who satisfied the inclusion/exclusion criteria. Only 12 patients (40%) received adequate weight-based dosing (weight-based, 30 mg/kg/day). Weight-based patients weighed significantly less than non-weight-based patients (62.7 vs. 84.2 kg, p = 0.0008). Weight-based patients were more likely to achieve therapeutic trough levels than non-weight-based patients (58 vs. 33%, p = 0.176). Of patients who achieved therapeutic trough levels, more weight-based patients achieved it at first trough than non-weight-based patients (33 vs. 5.6%, p = 0.046).

CONCLUSIONS

When prescribing commonly used dosing regimens, appropriate weight-based administration of vancomycin occurred in only approximately one-third of patients. Those patients who did receive weight-based vancomycin dosing were more likely to achieve therapeutic levels, both initially (33 vs. 5.6%) and overall (58 vs. 33%).

Prediction of failure in vancomycin-treated methicillin-resistant Staphylococcus aureus bloodstream infection: a clinically useful risk stratification tool

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of bloodstream infection (BSI) and is often associated with invasive infections and high rates of mortality. Vancomycin has remained the mainstay of therapy for serious Gram-positive infections, particularly MRSA BSI; however, therapeutic failures with vancomycin have been increasingly reported. We conducted a comprehensive evaluation of the factors (patient, strain, infection, and treatment) involved in the etiology and management of MRSA BSI to create a risk stratification tool for clinicians. This study included consecutive patients with MRSA BSI treated with vancomycin over 2 years in an inner-city hospital in Detroit, MI. Classification and regression tree analysis (CART) was used to develop a risk prediction model that characterized vancomycin-treated patients at high risk of clinical failure. Of all factors, the Acute Physiology and Chronic Health Evaluation II (APACHE-II) score, with a cutoff point of 14, was found to be the strongest predictor of failure and was used to split the population into two groups. Forty-seven percent of the population had an APACHE-II score < 14, a value that was associated with low rates of clinical failure (11%) and mortality (4%). Fifty-four percent of the population had an APACHE-II score ≥ 14, which was associated with high rates of clinical failure (35%) and mortality (23%). The risk stratification model identified the interplay of three other predictors of failure, including the vancomycin MIC as determined by Vitek 2 analysis, the risk level of the source of BSI, and the USA300 strain type. This model can be a useful tool for clinicians to predict the likelihood of success or failure in vancomycin-treated patients with MRSA bloodstream infection.

Characterization of vancomycin pharmacokinetics in the adult acute myeloid leukemia population

Current vancomycin dosing guidelines in our acute myeloid leukemia population too often achieve suboptimal initial drug concentrations. Our aim was to assess vancomycin pharmacokinetic parameters in acute myeloid leukemia patients and develop an improved dosing equation to attain more accurate initial therapeutic trough levels. Acute myeloid leukemia patients receiving vancomycin for a presumed or documented gram positive infection were eligible. Patients hospitalized in the intensive care unit, those with creatinine clearance <30 mL/min or with limb amputation were excluded. Three samples were collected at the following post-infusion time ranges: 1 h, 3-8 h, and 8-24 h post-infusion, contingent on the dosing interval. Pharmacokinetic data were then fit using a Bayesian-based population pharmacokinetic model. A total of 25 acute myeloid leukemia patients were studied with a mean volume in the central compartment (Vc; L/65 kg), volume of distribution at steady state (Vss; L/65 kg) and distributional clearance (CLd; L/h/65 kg) of 15, 38.9, and 9.32, respectively. CLslope was 0.59 (mg of vancomycin clearance per unit of creatinine clearance in mL/min); this value is 21.4% lower than the established literature value (0.75). The derived equation, based upon these values, was reasonably precise at achieving the desired trough concentration using a priori dosing. The mean (CV%) of the achieved trough was 94% (29%) with a range of 66-188%; 3/25 at <75% and >125%]. We have established that the derived dosing equation can place ≈ 75% of adult acute myeloid leukemia patients at vancomycin trough levels within 75-125% of the target trough level.

Comparative effectiveness of linezolid and vancomycin among a national cohort of patients infected with methicillin-resistant Staphylococcus aureus

While newer antibiotics play a key role in treating methicillin-resistant Staphylococcus aureus (MRSA) infections, knowledge of their real-world clinical impact is limited. We sought to quantify the effectiveness of linezolid compared to that of vancomycin among MRSA-infected patients. This national retrospective cohort study included adult patients admitted to all Veterans Affairs hospitals between January 2002 and June 2008, infected with MRSA, and treated with either linezolid (oral or intravenous [i.v.]) or vancomycin (i.v.). Patients were followed from their treatment initiation date until the event of interest, discharge, death, or December 2008. Utilizing propensity score methods, we estimated the treatment effects of linezolid primarily on time to discharge and secondarily on time to all-cause in-hospital mortality, therapy discontinuation, and all-cause 90-day readmission with Cox proportional-hazard models. We identified 20,107 patients treated with linezolid (3.2%) or vancomycin (96.8%). Baseline covariates were well balanced by treatment group within propensity score quintiles and between propensity score matched patients (626 pairs). The discharge rate was significantly higher among patients treated with linezolid, representing a decreased length of stay, in both the propensity score adjusted (hazard ratio [HR], 1.38; 95% confidence interval [95% CI], 1.27 to 1.50) and matched (HR, 1.70; 95% CI, 1.44 to 2.00) analyses. A significantly decreased rate of therapy discontinuation, indicating longer therapy duration, was observed in the linezolid group (adjusted HR, 0.64; 95% CI, 0.54 to 0.75; matched HR, 0.49; 95% CI, 0.36 to 0.65). In this clinical population of MRSA-infected patients, linezolid therapy was as effective as vancomycin therapy with respect to in-hospital survival and readmission.

Implementation and evaluation of vancomycin nomogram guidelines in a computerized prescriber-order-entry system

PURPOSE

The implementation and evaluation of vancomycin nomogram guidelines in a computerized prescriber-order-entry (CPOE) system are described.

METHODS

Initial vancomycin orders for patients over age 18 years who received vancomycin between August 1 and September 30, 2006 (preimplementation), and between March 1 and April 30, 2007 (postimplementation), were compared with vancomycin nomogram recommendations to determine if the vancomycin regimen ordered coincided with the nomogram recommendation. The numbers of regimen changes and vancomycin serum concentrations measured during the first five days of therapy were also assessed. A multivariate logistic regression model assessed independent predictors of an initial vancomycin order that met the nomogram recommendation

RESULTS

A total of 522 vancomycin orders were included in the analysis (279 in the preimplementation group and 243 in the postimplementation group). A significant difference was observed in the percentage of initial vancomycin orders that met nomogram recommendations in the postimplementation group compared with the preimplementation group (36% versus 24%, p = 0.0028). No difference was noted between the two groups in the number of regimen changes or serum vancomycin concentrations measured during the first five days of therapy. In a multivariate analysis, age (p = 0.02) and weight (p < 0.0001) were negatively associated with a vancomycin order that met nomogram recommendations, while the postimplementation group was positively associated with an order that met nomogram recommendations (p = 0.001).

CONCLUSION

A vancomycin nomogram implemented into a CPOE system increased the likelihood of patients receiving an initial vancomycin regimen that coincided with the nomogram's recommendations.

Optimizing Vancomycin Dosing through Pharmacodynamic Assessment Targeting Area under the Concentration-Time Curve/Minimum Inhibitory Concentration

Because of its activity against multidrug resistant gram-positive organisms, vancomycin is one of the antimicrobials most utilized in health care systems worldwide. Despite its widespread use, application of the pharmacodynamic principles governing vancomycin efficacy are not frequently considered in contemporary clinical practice. Although the vancomycin trough serum concentration has been used historically to assess the adequacy of a prescribed dose, data validating that this practice leads to improved patient outcomes do not exist. Alternatively, both in vitro and clinical outcomes data demonstrate improved results when an area under the concentration-time curve/minimum inhibitory concentration (AUC/MIC) of 400 mcg•h/mL or greater is achieved. This article describes the process through which individualized vancomycin dosing regimens targeting an AUC/MIC of 400 mcg•h/mL or greater, rather than trough serum concentration, at the beside can be derived. The equations, methodology, thought processes, benefits, potential pitfalls, and practical applicability of this method are specifically examined. Obtaining the actual MIC value—not an interpretation—from the microbiology laboratory and/or the MIC distribution for Staphylococcus aureus within one's own institution is essential for implementation of this method. Although vancomycin dosing recommendations suggested in contemporary practice guidelines are likely adequate for most patients, using the methods described here may lead to improved clinical outcomes for nonstandard conditions in patients who are critically ill and would benefit from an individualized dosing approach.

Medication-related complications in the trauma patient

Trauma patients are twice as likely to have adverse reactions to medication as nontrauma patients. The need for medication in trauma patients is high. Surgery is often necessary, and immunosuppression and hypercoagulability may be present. Adverse drug events can be caused in part by altered pharmacokinetics, drug interactions, and polypharmacy. Medications may also have serious long-term adverse effects, which must be considered. It is not the purpose of this review article to discuss all adverse effects of all medications. This article will discuss the more common adverse effects of medications for trauma patients in the acute care setting, in the following categories: pain control, sedation, antibiotics, seizure prophylaxis in head trauma, atrial fibrillation, deep vein thrombosis and pulmonary embolism prophylaxis, hemodynamic support, adrenal insufficiency, factor VIIa.

Vancomycin revisited: a reappraisal of clinical use

Vancomycin has been used for decades to treat serious systemic gram positive infections. Extensive use over time has demonstrated vancomycin is not nephrotoxic even when used in high dosage, i.e., twice the usual dose. Since vancomycin is not nephrotoxic, there is no rationale for dosing vancomycin based on serum vancomycin levels. Since vancomycin is eliminated by GFR, vancomycin dosing should be based on creatinine clearance. Vancomycin obeys "concentration dependent" kinetics and higher than usual doses may be useful in some infections (eg, osteomyelitis). Widespread vancomycin use has resulted in increased VRE prevalence worldwide. Among staphylococci, vancomycin induced cell wall thickening results in "permeability mediated" resistance to vancomycin, as well as other anti-staphylococcal antibiotics. "Permeability mediated" resistance accounts for the common clinical observation that MRSA infections treated with vancomycin often resolve slowly or not at all. Other effective MRSA antibiotics are available (eg, linezolid, daptomycin, minocycline, or tigecycline) and are more reliably effective, do not increase staphylococcal resistance or increase VRE prevalence.

Impact of empirical-therapy selection on outcomes of intravenous drug users with infective endocarditis caused by methicillin-susceptible Staphylococcus aureus

This study compares beta-lactam and vancomycin among intravenous drug users with infective endocarditis caused by methicillin-susceptible Staphylococcus aureus. Patients who received vancomycin had higher infection-related mortality, even if they were switched to beta-lactam once culture results became available; this relationship persisted after logistic regression analysis controlling for clinical characteristics.

Vancomycin for treatment of invasive, multi-drug resistant Staphylococcus aureus infections

Staphylococcus aureus is a bacterial pathogen responsible for a variety of serious infections and is a frequent cause of nosocomial disease. During the last 60 years, S. aureus has developed increasing in vitro resistance to virtually all antimicrobials. In contrast, vancomycin has maintained a high degree of activity in vitro against this pathogen, although slight changes with in vitro activity could vastly change clinical activity. As a result, vancomycin has become the mainstay of therapy for invasive infections due to methicillin-resistant strains. However, clinical strains of S. aureus with intermediate resistance to vancomycin were reported in 1996, followed in 2002 with reports of isolates that were fully resistant. Although many authorities believe vancomycin remains the drug of choice for most staphylococcal-resistant infections, important issues surrounding its clinical application remain. These include the need for multiple daily dosing, intravenous administration, requirements for serum concentration monitoring, increasing resistance in vitro, modest efficacy rates and (less frequently) treatment-limiting adverse effects. This review addresses these important topics.

Potential Impact of Vancomycin Pulmonary Distribution on Treatment Outcomes in Patients with Methicillin-ResistantStaphylococcus aureusPneumonia

Vancomycin as the drug of choice for treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia has been called into question on the basis of therapeutic failures. In patients with MRSA pneumonia, treatment failures are probably due to the complex interplay of variables affecting the host-antimicrobial-pathogen interrelationship. However, it has been suggested that decreased penetration of vancomycin into the lungs may contribute. This review explores physiochemical and physiologic variables that affect pulmonary penetration and describes methods used in quantifying pulmonary vancomycin concentrations. Most important, findings are evaluated in the clinical context of the chemotherapeutic options available for treatment of MRSA pneumonia. The possibility of increased serum vancomycin concentrations as a method to optimize current treatment outcomes is also explored.

Dehydroepiandosterone induction of increased resistance to vancomycin in Staphylococcus aureus clinical isolates (MSSA, MRSA)

AIMS

To investigate whether dehydroepiandosterone (DHEA), an androgen present throughout life, alters the response of Staphylococcus aureus clinical isolates to vancomycin.

METHODS AND RESULTS

DHEA in physiologically relevant concentrations (0.1, 0.5, 1.0 and 5.0 micromol l(-1)) was tested for its effect on methicillin-sensitive S. aureus (MSSA, n = 53) and methicillin-resistant S. aureus (MRSA, n = 73) response to vancomycin using standard protocols. Mutant selection was determined by serial transfer of selected isolates (n = 5). DHEA-mediated at least a fourfold increase in vancomycin MIC for 42% of MSSA and 21% of MRSA. For five of the isolates (0.1 and 0.5 micromol l(-1) DHEA) the MIC was increased to levels (8 microg ml(-1)) defined as vancomycin-intermediate resistance.

CONCLUSION

Resistance was detected only in the presence of DHEA, and was not related to altered generation time, indicating induction of phenotypic resistance.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings require further investigation to determine what role DHEA plays in clinical vancomycin treatment failure that has been reported in the absence of vancomycin genotypic resistance or heteroresistance.