Characterization of vancomycin pharmacokinetics in the adult acute myeloid leukemia population

Determination of a vancomycin nephrotoxicity threshold and assessment of target attainment in hematology patients

An area-under-the-curve (AUC24)-based approach is recommended to guide vancomycin therapeutic drug monitoring (TDM), yet trough concentrations are still commonly used despite associated risks. A definitive toxicity target is lacking, which is important for hematology patients who have a higher risk of nephrotoxicity. The aims were to (1) assess the impact of trough-based TDM on acute kidney injury (AKI) incidence, (2) establish a vancomycin nephrotoxicity threshold, and (3) evaluate the proportion of hematology patients achieving vancomycin therapeutic targets. Retrospective data was collected from 100 adult patients with a hematological malignancy or aplastic anemia who received vancomycin between April 2020 and January 2021. AKI occurrence was determined based on serum creatinine concentrations, and individual pharmacokinetic parameters were estimated using a Bayesian approach. Receiver operating characteristic (ROC) curve analysis was performed to assess the ability of pharmacokinetic indices to predict AKI occurrence. The proportion of patients who achieved target vancomycin exposure was evaluated based on an AUC24/MIC ≥400 and the determined toxicity threshold. The incidence of AKI was 37%. ROC curve analysis indicated a maximum AUC24 of 644 mg.h/L over the treatment period was an important predictor of AKI. By Day 4 of treatment, 29% of treatment courses had supratherapeutic vancomycin exposure, with only 62% of courses achieving AUC24 targets. The identified toxicity threshold supports an AUC24 target range of 400-650 mg.h/L, assuming an MIC of 1 mg/L, to optimize vancomycin efficacy and minimize toxicity. This study highlights high rates of AKI in this population and emphasizes the importance of transitioning from trough-based TDM to an AUC-based approach to improve clinical outcomes.

Toward Model-Based Informed Precision Dosing of Vancomycin in Hematologic Cancer Patients: A First Step

BACKGROUND AND OBJECTIVE

There is no consensus on the optimal vancomycin dose to achieve pharmacokinetic/pharmacodynamic (PK/PD) target in patients with hematologic cancer or in hematopoietic stem cell transplant (HSCT) recipients. A 24-h area under the concentration-time curve (AUC) >400 mg*h/L must be achieved early for successful treatment of severe methicillin-resistant Staphylococcus aureus (MRSA) infections. Current nomograms derived from general population data are not sufficiently accurate to allow AUC-based model-informed precision dosing. The objective of this study was to characterize vancomycin PK in patients with hematologic cancer or in HSCT recipients and to develop a model-informed dosing tool based on PK/PD target requirements.

METHODS

Pooled retrospective and prospective vancomycin serum concentrations were analyzed using NONMEM® to evaluate the performance of previously published population PK (popPK) models built from hematologic cancer datasets and to develop a novel Bayesian PK model. Patients' characteristics and clinical data were tested as potential covariates. The popPK model was validated internally and externally. Predictions of vancomycin concentrations for different dosing regimens were made using Monte-Carlo simulations, and a nomogram strategy was proposed according to selected probability of target attainment (PTA).

RESULTS

The predictive performance of the published popPK models was found to be suboptimal for our population. A novel popPK model was developed using 240 vancomycin concentrations (60 patients). A two-compartment structural model with an additive error model best described the data. Ideal body weight and estimated glomerular filtration rate (eGFR) [Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)] were selected as covariates for volume of distribution (V) and clearance (CL). Bootstrapping confirmed the stability and precision of the popPK parameters. The volume of distribution was V1 = 46.8 L and V2 = 56.1 L, while CL = 5.63 L/h. External validation using 107 vancomycin concentrations (24 patients) demonstrated the predictivity of the model. A nomogram was developed to reach minimally PTA >50% for 400 < AUC < 600 mg*h/L.

CONCLUSION

To our knowledge, this study provides the first model-informed AUC-based strategy in North American hematologic cancer patients with or without HSCT. The resulting nomogram generated provides a simplified approach to improving the accuracy of initial vancomycin dosing in this population.

Altered Pharmacokinetics Parameters of Vancomycin in Patients with Hematological Malignancy with Febrile Neutropenia, a Bayesian Software Estimation

The pharmacokinetics of vancomycin vary significantly between specific groups of patients, such as critically ill patients and patients with hematological malignancy (HM) with febrile neutropenia (FN). Recent evidence suggests that the use of the usual standard dose of antibiotics in patients with FN may not offer adequate exposure due to pharmacokinetic variability (PK). Therefore, the purpose of this study is to assess the effect of FN on AUC_0-24 as a key parameter for vancomycin monitoring, as well as to determine which vancomycin PK parameters are affected by the presence of FN using Bayesian software PrecisePK in HM with FN. This study was carried out in King Abdulaziz Medical City. All adult patients who were admitted to the Princess Norah Oncology Center PNOC between 1 January and 2017 and 31 December 2020, hospitalized and received vancomycin with a steady-state trough concentration measured before the fourth dose, were included. During the trial period, 297 patients received vancomycin during their stay at the oncology center, 217 of them meeting the inclusion criteria. Pharmacokinetic parameters were estimated for the neutropenic and non-FN patients using the precise PK Bayesian platform. The result showed that there was a significant difference (p < 0.05) in vancomycin clearance Cl_van, the volume of distribution at a steady-state V_dss, the volume of distribution for peripheral compartment V_dp, half-life for the elimination phase t½_β, and the first-order rate constant for the elimination process β in FN compared to non-FN patients. Furthermore, AUC_0-24 was lower for FN patients compared to non-FN patients, p < 0.05. FN has a significant effect on the PK parameters of vancomycin and AUC_0-24, which may require specific consideration during the treatment initiation.

Pharmacokinetics of Vancomycin among Patients with Chemotherapy-Associated Febrile Neutropenia: Which Would Be the Best Dosing to Obtain Appropriate Exposure?

Previous research has determined that the required doses for treating febrile neutropenia with vancomycin are higher than the doses used conventionally. These recommendations have been made considering pharmacotherapeutic goals based on minimum concentration (Cmin) between 15–20 mg/L. This study was developed to evaluate dose recommendations based on the achievement of a target consisting of ratio of area under the curve over minimum inhibitory concentration (AUC24h/MIC) ≥400 in this population of individuals. This study was conducted in a referral hospital for cancer treatment, study participants received vancomycin doses of 1g every 12 h in 2-4-h infusions. Vancomycin was described by a two-compartment pharmacokinetic model with clearance dependent on the estimated glomerular filtration rate. Simulations were performed taking into account a reduced version of the model to establish the influence of controllable and non-controllable variables on the probability of achieving several PK-PD targets. A dose of 2.5g/day in patients with estimated glomerular filtration rate (eGFR) between 80 and 122mL/min/1.73m2 was adequate to achieve the pharmacotherapeutic target. A discrepancy was found between AUC-based and Cmin-based PK/PD indices, the former being affected by the dose and creatinine clearance while the latter highly influenced by the interval between doses.

Population Pharmacokinetics of Vancomycin in Adult Patients with Long Bones’ Fractures

Vancomycin is a tricyclic glycopeptide antibiotic, mostly used in the treatment of severe staphylococcal and enterococcal infections, especially in orthopedic surgery.

The purpose of this analysis was to develop a population pharmacokinetic (PPK) model of vancomycine in hospitalized patients with bone fractures and identify important factors which influence its clearance (CL).

A total of ninety-nine measurements of vancomycin serum concentrations were used in our population modeling. A two-compartment model was applied to describe the pharmacokinetics of vancomycin using subroutines ADVAN3 and TRANS4.

The study population included patients of both sexes, with the mean age of 62.12±14.69 years and body weight of 80.32±12.44kg. Vancomycin was administered as intravenous infusion with average daily dose of 1772.73±521.34mg. Out of twenty different factors evaluated in the study (including demographic, clinical and laboratory data), only daily dose of vancomycin (DD) and co-medication with piperacillin/tazobactam (PT) showed significant effect on clearance of vancomycin. The final model was described by the following equation: CL (l/h) = 0.03 + 0.000468 x DD + 0.675 x PT. Bootstrapping was used for validation of the final model.

In conclusion, the main causes of variability in the clearance of vancomycin among adult patients with bone fractures are daily dose of vancomycin and co-medication with piperacillin/tazobactam.

Clinical application of vancomycin population pharmacokinetics model in patients with hematological diseases and neutropenia

To explore the clinical application of a population pharmacokinetics (PPK) model of vancomycin in patients with hematological diseases and neutropenia. Patients with hematological diseases and neutropenia were included in the PPK model study. Nonlinear mixed effect modeling approach (NONMEM) was used for model establishment. Monte Carlo simulation was carried out. A total of 74 patients were divided into model group and non-model group for clinical application research. The model group was given the initial dose of 1g q8h, and the non-model group was given 1g q12h as an empiric initial dosage. The follow-up dose adjustments were made according to the concentration results. This two-compartment model showed good stability and accuracy. The first trough concentration (C0 ) and the compliance rate of the first C0 were much higher in the model group than that in the non-model group (14.30 ± 4.73 μg/ml and 59.38% vs. 8.02 ± 2.61 μg/ml, 35.71%). Less patients needed dose adjustments and fewer adjustment times in the model group than those in the non-model group (12.50% and 0.13 ± 0.34 times vs. 50.00% and 0.61 ± 0.66 times). This suggested that for those patients who had a Creatinine clearance rate (CLCR) ≥ 90 ml/min/1.73 m2 , the initial dose of 1g q8h may help to reach the target C0 (10∼20 μg/ml) quickly. It also helped to reduce the times and number of patients who need dose adjustments. Our PPK model of vancomycin in patients with hematologic diseases and neutropenia can be used to shorten the time to reach the target concentration and reduce the number of dose adjustments.Clinical trial registration: Not applicable (Retrospective study).

Causes of vancomycin dosing error; problem detection and practical solutions; a retrospective, single-center, cross-sectional study

Vancomycindosing error and inappropriate monitoring is a common problem in hospital daily practice. In King Abdulaziz Medical City (KAMC) in Jeddah, a high percentage of abnormal vancomycin trough levels is still detected despite using the recommended dose. Therefore, the current research objective is to study the major causes of vancomycin dosing errors. This retrospective, single-center, cross-sectional study was carried out at KAMC hospital in Jeddah from January 1st until December 31st 2019. All adult patients (≥15 years) who received vancomycin and had an initial abnormal trough level at the measured steady-state were included in this study. 472 patients have met the study inclusion criteria.

The current study evaluated the factors that play a role in causing vancomycin trough level abnormalities such as sampling time, vancomycin dosing, and patient’s pharmacokinetic and pharmacodynamic variations.

In this study, we found that pharmacokinetic and pharmacodynamic variability was attributed to 65% of vancomycin's abnormal trough level. Also, the result showed a significantly increased odds of the low trough in the non-elderly group (OR 6, 95% CI 2.48 – 14.9, P < 0.001) and febrile neutropenic patients (OR 2.21, 95% CI 1.119 – 4.365, P < 0.05). However, the odds of high trough levels were significantly elevated among patients who have CrCl < 50 ml/min (OR 5, 95% CI 1.262–20.539, P < 0.05). In addition, the present investigation revealed that the occurrence of abnormal vancomycin levels was not affected by daily duty time or working days (p > 0.05). The current study indicated that vancomycin dosing errors were common in KAMC patients; thus, there is an unmet need to evaluate the causes of vancomycin abnormal trough level and optimize a strategy that would enhance the therapeutic effectiveness and minimize the potential toxicity.

Contribution of Population Pharmacokinetics of Glycopeptides and Antifungals to Dosage Adaptation in Paediatric Onco-hematological Malignancies: A Review

The response to medications in children differs not only in comparison to adults but also between children of the different age groups and according to the disease. This is true for anti-infectives that are widely prescribed in children with malignancy. In the absence of pharmacokinetic/pharmacodynamic paediatric studies, dosage is frequently based on protocols adapted to adults. After a short presentation of the drugs, we reviewed the population pharmacokinetic studies available for glycopeptides (vancomycin and teicoplanin, n = 5) and antifungals (voriconazole, posaconazole, and amphotericin B, n = 9) currently administered in children with onco-hematological malignancies. For each of them, we reported the main study characteristics including identified covariates affecting pharmacokinetics and proposed paediatric dosage recommendations. This review highlighted the very limited amount of data available, the lack of consensus regarding PK/PD targets used for dosing optimization and regarding dosage recommendations when available. Additional PK studies are urgently needed in this specific patient population. In addition to pharmacokinetics, efficacy may be altered in immunocompromised patients and prospective clinical evaluation of new dosage regimen should be provided as they are missing in most cases.

Vancomycin pharmacokinetic parameters in patients undergoing hematopoietic stem cell transplantation

INTRODUCTION

Current guidelines on vancomycin dosing lack specific recommendations about its dosing in hematopoietic stem cell transplant (HSCT) patients, the objective of the current study was to compare vancomycin pharmacokinetic variables in this population with those of general population.

METHODS

A prospective study was designed and the calculated parameters of vancomycin pharmacokinetic were compared with individualized parameters. Two trough levels before 4th and 5th doses and a peak level after the 4th dose, were taken. All patients received a dose of 15 mg/kg of vancomycin two or three times a day. Pharmacokinetic parameters were calculated using a one compartmental model. The association between different variables and of acute kidney injury (AKI) development and achievement of target levels were also evaluated.

RESULTS

A significant difference was observed between population Volume of distribution (Vd) and individualized Vd (mean 57.33 L vs 162.86 L, p value 0.019) and trough and peak levels (p values 0.0001 and 0.001; for mean trough and peak levels respectively). The achievement of the recommended trough levels and area under the concentration time curve per minimum inhibitory concentration (AUC24/MIC) was very low (5/71 and 24/71 patients respectively). No significant differences were observed between population and individualized clearance and rate of elimination of vancomycin (p values of 0.092 and 0.55 respectively). Concomitant receipt of cyclosporine was significantly related with development of AKI (p value 0.046).

CONCLUSION

The dosing methods which use population-based pharmacokinetic variables does not result in desired therapeutic levels in HSCT patients, mainly because of larger vancomycin volume of distribution.

A Systematic Review of Vancomycin Dosing in Patients with Hematologic Malignancies or Neutropenia

Objective

To provide a comprehensive review of vancomycin dosing in patients with hematologic malignancies or neutropenia.

Methods

PubMed, Embase and the Cochrane Library were searched through April 2, 2020. Original studies relevant to vancomycin dosing regimen in adults with hematologic malignancies or neutropenia were included. No restriction was applied in study design and language. A descriptive analysis was performed.

Results

Twenty-three studies were included eventually, of which eighteen were case series studies, four were cohort studies and another one was a randomized controlled trial. Five case series studies made a clinical audit of conventional vancomycin dosing in patients with malignancies or neutropenia, showing that the proportion of patients with sub-therapeutic trough levels remained high, ranging from 32% to 88%. Seven case series studies and four cohort studies demonstrated that vancomycin clearance (CLva) tended to be higher in patients with hematologic malignancies or neutropenia, whereas volume of distribution (V) seemed to be comparable to the control group. Five studies proposed individualized initial dosing regimen per the pharmacokinetic changes; however, no prospective validation has been conducted in clinical setting. Additionally, four case series studies suggested that the correlation between vancomycin clearance and estimated creatinine clearance was relatively poor, bringing a great challenge to proper dosing strategy. A randomized controlled trial stated that therapeutic drug monitoring (TDM) of vancomycin could decrease the incidence of nephrotoxicity in immunocompromised febrile patients with hematologic malignancies.

Conclusion

The available evidence indicates that conventional vancomycin dosing leads to suboptimal concentration in patients with hematologic malignancy or neutropenia. TDM accompanied by pharmacokinetic interpretation can decrease the risk of nephrotoxicity. The individualization of the initial dosing regimen and mechanisms of augmented clearance require further research.

Pharmacokinetics of Vancomycin in Patients with Different Renal Function Levels

There are many determinants of vancomycin clearance, but these have not been analyzed separately in populations with different levels of renal function, which could be why some important factors have been missed. The aim of our study was to compare the pharmacokinetic parameters and factors that may affect vancomycin pharmacokinetics in groups of patients with normal renal function and in those with chronic kidney failure. The study used a population pharmacokinetic modeling approach, based on plasma vancomycin concentrations and other data from 78 patients with chronic kidney failure and 32 patients with normal renal function. The model was developed using NONMEM software and validated by bootstrapping. The final model for patients with impaired kidney function was described by the following equation: CL (L/h) = 0.284 + 0.000596 x DD + 0.00194 x AST, and that for the patients with normal kidney function by: CL (L/h) = 0.0727 + 0.205 x FIB. If our results are confirmed by new studies on two similar populations, these factors could be considered when dosing vancomycin in patients with chronically damaged kidneys, as well as in patients with normal kidneys who frequently require high doses of vancomycin.

Vancomycin therapeutic drug monitoring and population pharmacokinetic models in special patient subpopulations

Vancomycin is a fundamental antibiotic in the management of severe Gram-positive infections. Inappropriate vancomycin dosing is associated with therapeutic failure, bacterial resistance and toxicity. Therapeutic drug monitoring (TDM) is acknowledged as an important part of the vancomycin therapy management, at least in specific patient subpopulations, but implementation in clinical practice has been difficult because there are no consensus and agglutinator documents. The aims of the present work are to present an overview of the current knowledge on vancomycin TDM and population pharmacokinetic (PPK) models relevant to specific patient subpopulations. Based on three published international guidelines (American, Japanese and Chinese) on vancomycin TDM and a bibliographic review on available PPK models for vancomycin in distinct subpopulations, an analysis of evidence was carried out and the current knowledge on this topic was summarized. The results of this work can be useful to redirect research efforts to address the detected knowledge gaps. Currently, TDM of vancomycin presents a moderate level of evidence and practical recommendations with great robustness in neonates, pediatric and patients with renal impairment. However, it is important to investigate in other subpopulations known to present altered vancomycin pharmacokinetics (eg neurosurgical, oncological and cystic fibrosis patients), where evidence is still unsufficient.

Prospective evaluation of vancomycin pharmacokinetics in a heterogeneous critically ill population

Rich pharmacokinetic data on vancomycin in critically ill patients are lacking. The purpose of this study was to evaluate the pharmacokinetics of vancomycin in this population using rich pharmacokinetic sampling. Nineteen critically ill patients received individualized vancomycin doses by intermittent infusion to achieve target trough concentrations (15-20 mg/L). Blood samples were collected following the third or later dose of vancomycin. Serial blood samples were collected at 30 min following initiation of the vancomycin infusion; at the end of the infusion; serially at 60, 120, 300, and 480 min after the infusion finished; and immediately prior to the next dose. Vancomycin concentration-time profiles at steady state were fit to a noncompartmental model to determine the pharmacokinetic parameters. Vancomycin trough concentration was correlated to AUC_0-24 (r = 0.83, P < 0.001). Total body weight was a predictor of volume of distribution (r = 0.43, P = 0.03). Age, serum creatinine, and creatinine clearance (CrCl) were found to be predictors for vancomycin clearance (r = -0.67, -0.52, and, 0.72, respectively). CrCl was the best predictor of vancomycin systemic clearance, and addition of other variables to a multivariate model failed to improve model fit. Vancomycin trough concentration may not be an adequate surrogate of AUC_0-24. Additional research is needed to determine dosing strategies to optimize AUC_0-24 while limiting toxicity.

Pediatric Patients With Solid or Hematological Tumor Disease: Vancomycin Population Pharmacokinetics and Dosage Optimization

BACKGROUND

In pediatric cancer patients, determination of optimal vancomycin dosage is essential because of high risk of inadequate concentrations and bacterial resistance. The aim of this study was to determine vancomycin pharmacokinetic parameters in this population and propose dosage optimization to achieve optimal concentration.

METHODS

We retrospectively reviewed the use of vancomycin in pediatric cancer patients with febrile neutropenia (hematological or solid tumor disease). Vancomycin was administered by continuous infusion, and dosages were adapted according to therapeutic drug monitoring results. Blood cultures were performed before the first dose of antibiotic. Vancomycin pharmacokinetic population parameters were determined using NONMEM software, and dosage simulations were performed according to the target concentration (20-25 mg/L).

RESULTS

One hundred twenty-one patients were included in this study, representing 301 vancomycin concentrations. Blood cultures were positive in 37.5% of patients, and observed pathogens were mainly Staphylococcus spp. (43.8% methicillin resistant). Volume of distribution (95% confidence interval) was 34.7 L (17.3-48.0), and total apparent clearance (CL) (95% confidence interval) was correlated to body weight, tumor disease, and cyclosporine coadministration: CL = θCL × (WT/70) L/h with θCL = 3.49 (3.02-3.96), 4.66 (3.98-5.31), and 4.97 (4.42-5.41) in patients managed for hematological malignancies with or without cyclosporine coadministration and for solid malignancies, respectively. Based on simulation results, vancomycin dosage (milligram per kilogram) should be adapted to each child on the basis of its body weight and cyclosporine coadministration.

CONCLUSIONS

Our results highlight the requirement to adapt vancomycin dosage in cancer pediatric population. Simulations have allowed to describe new dosage schedules, and a chart was created for clinicians to adapt vancomycin dosage.

Variability in Trough Total and Unbound Teicoplanin Concentrations and Achievement of Therapeutic Drug Monitoring Targets in Adult Patients with Hematological Malignancy

The objective of this study was to explore the following aspects of teicoplanin use in patients with hematological malignancy: early attainment of target trough concentrations with current high-dose teicoplanin regimens, variability in unbound teicoplanin fractions, factors associated with observed total and unbound trough concentrations, efficacy and toxicity, and renal function estimation. This was a single-center, prospective study. Samples for determination of trough concentrations were taken on days 3, 4, 7, and 10. Total and unbound teicoplanin concentrations were determined using validated high-performance liquid chromatography methods. Regression analyses were used to identify the factors associated with the trough concentration. Thirty teicoplanin-treated adults with hematological malignancy were recruited. Despite the use of dosages higher than the conventional dosages, the proportions of patients with a trough concentration of ≥20 mg/liter at 48 h and at 72 h were 16.7% and 37.9%, respectively. Renal function was significantly negatively associated with total trough concentrations at 48 h and 72 h (P < 0.05). For an average hematological malignancy patient (creatinine clearance = 70 ml/min), sequential loading doses of at least 12 mg/kg of body weight may be needed to achieve early adequate exposure. In the absence of measured creatinine clearance, estimates obtained using the Cockcroft-Gault (total body weight) equation could prove to be an acceptable surrogate. The unbound fractions of teicoplanin were highly variable (3.4 to 18.8%). Higher unbound fractions were observed in patients with low serum albumin concentrations. Teicoplanin was well tolerated. Teicoplanin loading doses higher than those in current use appear to be necessary. Increased dosing is needed in patients with increased renal function. The high variability in protein binding supports the contention for therapeutic drug monitoring of unbound teicoplanin concentrations. (This study has been registered with EudraCT under registration no. 2013-004535-72.).

Identification of Risk Factors for Initial Elevated Vancomyin Trough Concentrations

Background: Recent literature suggests that elevated vancomycin trough concentrations (>20 µg/mL) may be associated with an increased risk of nephrotoxicity and lead to an increase in mortality and hospital length of stay. Objective: The purpose of this study was to identify variables that may be predictive of elevated initial vancomycin trough concentrations. Methods: Retrospective case–control study of all adult patients who had an initial vancomycin trough concentration measured between January 1, 2013, and December 31, 2014. Case patients had an initial trough concentration >20 µg/mL, while control patients had an initial trough concentration of ≤20 µg/mL. Patients were excluded from the study if they were in the intensive care unit, had unstable renal function, or if they had cystic fibrosis, solid organ transplant, or bone marrow transplant. Results: Of the 512 vancomycin trough concentrations reviewed, 54 patients met the case definition, while 140 patients were randomly selected as controls. In a multivariate model, baseline serum creatinine, body mass index, heart failure, and malignancy were all independently predictive of an initial vancomycin concentration >20 µg/mL. Conclusions: Reduced baseline renal function coupled with increasing body mass index is associated with an increased risk of an elevated initial vancomycin trough concentration. This risk is further enhanced by the presence of heart failure and/or malignancy. When these risk factors are present, it may be prudent to consider implementation of individualized dosing to achieve initial target concentrations.

Predictive performance of Vancomycin population pharmacokinetic models in Iranian patients underwent hematopoietic stem cell transplantation

Objective:

Many hematopoietic stem cell transplantation (HSCT) patients receive vancomycin empirically during febrile neutropenia. There are several models for estimation of vancomycin pharmacokinetic parameters and calculation of initial dosing regimen accordingly. However, the performance of these methods in HSCT patients remained to be evaluated. The aim of the study was to determine which of the vancomycin population pharmacokinetic methods best fit Iranian HSCT patients.

Methods:

In order to evaluate predicted performance of seven vancomycin population pharmacokinetic models, the pharmacokinetic parameters of patients were estimated using each model's equations. Then the predicted steady-state trough vancomycin concentration was calculated based on each model's parameters and using a formula based on Sawchuk–Zaske method. The predicted steady-state trough vancomycin concentration and the real measured concentrations were compared to see which method was the most precise and least biased using mean squared error (MSE) and mean prediction error (ME) respectively.

Findings:

Forty-six patients (65% men) were included in the study. Calculated metrics showed a range of 38% under-prediction bias with Rodvold to 34% over-prediction bias with Matzke and Burton models. Birt and revised Burton methods showed no significant bias (ME [95% confidence interval (CI)]: –0.067 [–0.235–0.101] and 0.066 [–0.105–0.238]). Birt and revised Burton were not different significantly considering MSE (95% CI) of 0.385 (0.227–0.544) and 0.401 (0.255–0.546), respectively. Comparisons of precision with naive predictors revealed a delta MSE (95% CI) of –0.128 (–1.379–1.890) for Birt and 0.026 (–0.596–0.940) for revised Burton models.

Conclusion:

Although the Birt and Burton revised methods performed well, none of the studied models showed acceptable performance to be implemented as a routine method for initial dose calculation in HSCT patients. A vancomycin pharmacokinetic model specific for this high-risk subpopulation of Iranian patients should be designed and validated.

Teicoplanin use in adult patients with haematological malignancy: Exploring relationships between dose, trough concentrations, efficacy and nephrotoxicity

In 2010, our hospital introduced a higher target teicoplanin trough concentration of ≥20 mg/L by Day 3 for haematological malignancy patients. This study aimed to explore whether target trough concentrations were achieved, to identify factors associated with trough concentrations attained, and to assess clinical efficacy with teicoplanin treatments and nephrotoxicity. This was a retrospective, single-centre, cohort study of 172 teicoplanin treatments in 104 adults with haematological malignancy. Mixed-effects regression was used to evaluate factors affecting trough concentrations, and logistic regression was used to assess the relationship between trough concentrations and treatment outcomes. Nephrotoxicity was assessed using the RIFLE criteria. Considerable variability in trough concentrations was observed, with trough concentrations ≥20 mg/L rarely achieved early in therapy. A mixed-effects regression model explaining 52% of the variation in trough concentrations was developed. Dose and day of therapy were positively associated with trough concentration, whilst estimated renal function and, interestingly, acute myeloid leukaemia diagnosis were negatively associated (P<0.05). Results suggested a positive relationship between trough concentration and the likelihood of a favourable outcome for coagulase-negative staphylococcal central line-associated bloodstream infections. Elucidation of a specific target concentration requires further investigation. Teicoplanin was well tolerated renally. Findings suggest a risk of underexposure if conventional teicoplanin doses are used in haematological malignancy patients. Given the variability in trough concentrations observed, the identified factors affecting trough concentrations attained and the suggested link with clinical outcome, individualised initial dosing followed by therapeutic drug monitoring is recommended to ensure early adequate exposure in this vulnerable patient group.