Association of aminoglycoside plasma levels with therapeutic outcome in gram-negative pneumonia

A phase I clinical study: Evaluation of safety, tolerability, and population pharmacokinetic-pharmacodynamic target attainment analysis of etimicin sulfate among healthy chinese participants

BACKGROUND

This phase I clinical study aimed to assess the safety, tolerability, and population pharmacokinetic-pharmacodynamics (PK-PD) target attainment analysis of etimicin sulfate in healthy participants, and to provide scientific reference for further development of clinical breakpoints.

METHODS

A total of 24 healthy Chinese subjects were enrolled in this study and received an etimicin sulfate infusion. A population PK model was constructed for the estimation of the PK profiles of etimicin sulfate. The area under the concentration-time curve divided by the minimum inhibitory concentration (AUC0-24h/MIC) and the peak concentration divided by the MIC (Cmax/MIC) were selected as the PK/PD indices. The probability of target attainment (PTA) was calculated for each designed dosing regimen using Monte Carlo simulations. The minimum MIC value with a PTA ≥ 90% for each regimen was considered as the PK/PD cutoff values.

RESULTS

Etimicin sulfate demonstrated safety, tolerability, and predictable PK characteristics. No deaths or serious adverse events were reported. Seven treatment-emergent adverse events (TEAEs) were reported by five participants; all TEAEs were minor and were rapidly relieved. A two-compartment model was developed and validated for describing the PK features of etimicin sulfate among Chinese healthy participants. The diagnostic goodness-of-fit plots and visual predictive check plots showed that this developed model could describe these data well.

CONCLUSIONS

The PTA results showed that etimicin sulfate provided clinical improvement against strains with an MIC of 0.5-1 mg/L and below, and antibacterial effect against strains with an MIC of 0.25 mg/L and below. However, etimicin sulfate had limited clinical efficacy for clinical isolates with MIC values > 1 mg/L.

Management of Complex Infections in Hemophagocytic Lymphohistiocytosis in Adults

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of excessive immune system activation and inflammatory response due to a variety of primary and secondary factors that can cause a range of clinical symptoms and, in severe cases, life-threatening conditions. Patients with HLH are at increased risk of infection due to their abnormal immune function as well as chemotherapy and immunosuppressive therapy at the time of treatment. At the same time, the lack of specific clinical features makes complex infections in HLH challenging to diagnose and treat. The management of complex infections in HLH requires a multidisciplinary and integrated approach including the early identification of pathogens, the development of anti-infection protocols and regimens, and the elimination of potential infection factors. Especially in HLH patients with septic shock, empirical combination therapy against the most likely pathogens should be initiated, and appropriate anti-infective regimens should be determined based on immune status, site of infection, pathogens, and their drug resistance, with timely antibiotic adjustment by monitoring procalcitonin. In addition, anti-infection prophylaxis for HLH patients is needed to reduce the risk of infection such as prophylactic antibiotics and vaccinations. In conclusion, complex infection in HLH is a serious and challenging disease that requires vigilance, early identification, and timely anti-infective therapy.

Evaluation of Dosing Guidelines for Gentamicin in Neonates and Children

Although aminoglycosides are frequently prescribed to neonates and children, the ability to reach effective and safe target concentrations with the currently used dosing regimens remains unclear. This study aims to evaluate the target attainment of the currently used dosing regimens for gentamicin in neonates and children. We conducted a retrospective single-center cohort study in neonates and children receiving gentamicin between January 2019 and July 2022, in the Beatrix Children's Hospital. The first gentamicin concentration used for therapeutic drug monitoring was collected for each patient, in conjunction with information on dosing and clinical status. Target trough concentrations were ≤1 mg/L for neonates and ≤0.5 mg/L for children. Target peak concentrations were 8-12 mg/L for neonates and 15-20 mg/L for children. In total, 658 patients were included (335 neonates and 323 children). Trough concentrations were outside the target range in 46.2% and 9.9% of neonates and children, respectively. Peak concentrations were outside the target range in 46.0% and 68.7% of neonates and children, respectively. In children, higher creatinine concentrations were associated with higher gentamicin trough concentrations. This study corroborates earlier observational studies showing that, with a standard dose, drug concentration targets were met in only approximately 50% of the cases. Our findings show that additional parameters are needed to improve target attainment.

Clinical Pharmacokinetics of Gentamicin in Various Patient Populations and Consequences for Optimal Dosing for Gram-Negative Infections: An Updated Review

Gentamicin is an aminoglycoside antibiotic with a small therapeutic window that is currently used primarily as part of short-term empirical combination therapy. Gentamicin dosing schemes still need refinement, especially for subpopulations where pharmacokinetics can differ from pharmacokinetics in the general adult population: obese patients, critically ill patients, paediatric patients, neonates, elderly patients and patients on dialysis. This review summarizes the clinical pharmacokinetics of gentamicin in these patient populations and the consequences for optimal dosing of gentamicin for infections caused by Gram-negative bacteria, highlighting new insights from the last 10 years. In this period, several new population pharmacokinetic studies have focused on these subpopulations, providing insights into the typical values of the most relevant pharmacokinetic parameters, the variability of these parameters and possible explanations for this variability, although unexplained variability often remains high. Both dosing schemes and pharmacokinetic/pharmacodynamic (PK/PD) targets varied widely between these studies. A gentamicin starting dose of 7 mg/kg based on total body weight (or on adjusted body weight in obese patients) appears to be the optimal strategy for increasing the probability of target attainment (PTA) after the first administration for the most commonly used PK/PD targets in adults and children older than 1 month, including critically ill patients. However, evidence that increasing the PTA results in higher efficacy is lacking; no studies were identified that show a correlation between estimated or predicted PK/PD target attainment and clinical success. Although it is unclear if performing therapeutic drug monitoring (TDM) for optimization of the PTA is of clinical value, it is recommended in patients with highly variable pharmacokinetics, including patients from all subpopulations that are critically ill (such as elderly, children and neonates) and patients on intermittent haemodialysis. In addition, TDM for optimization of the dosing interval, targeting a trough concentration of at least < 2 mg/L but preferably < 0.5–1 mg/L, has proven to reduce nephrotoxicity and is therefore recommended in all patients receiving more than one dose of gentamicin. The usefulness of the daily area under the plasma concentration–time curve for predicting nephrotoxicity should be further investigated. Additionally, more research is needed on the optimal PK/PD targets for efficacy in the clinical situations in which gentamicin is currently used, that is, as monotherapy for urinary tract infections or as part of short-term combination therapy.

Therapeutic Drug Monitoring of Antibiotics: Defining the Therapeutic Range

PURPOSE

In the present narrative review, the authors aimed to discuss the relationship between the pharmacokinetic/pharmacodynamic (PK/PD) of antibiotics and clinical response (including efficacy and toxicity). In addition, this review describes how this relationship can be applied to define the therapeutic range of a particular antibiotic (or antibiotic class) for therapeutic drug monitoring (TDM).

METHODS

Relevant clinical studies that examined the relationship between PK/PD of antibiotics and clinical response (efficacy and response) were reviewed. The review (performed for studies published in English up to September 2021) assessed only commonly used antibiotics (or antibiotic classes), including aminoglycosides, beta-lactam antibiotics, daptomycin, fluoroquinolones, glycopeptides (teicoplanin and vancomycin), and linezolid. The best currently available evidence was used to define the therapeutic range for these antibiotics.

RESULTS

The therapeutic range associated with maximal clinical efficacy and minimal toxicity is available for commonly used antibiotics, and these values can be implemented when TDM for antibiotics is performed. Additional data are needed to clarify the relationship between PK/PD indices and the development of antibiotic resistance.

CONCLUSIONS

TDM should only be regarded as a means to achieve the main goal of providing safe and effective antibiotic therapy for all patients. The next critical step is to define exposures that can prevent the development of antibiotic resistance and include these exposures as therapeutic drug monitoring targets.

Potential Antibiotics for the Treatment of Neonatal Sepsis Caused by Multidrug-Resistant Bacteria

Neonatal sepsis causes up to an estimated 680,000 deaths annually worldwide, predominantly in low- and middle-income countries (LMICs). A significant and growing proportion of bacteria causing neonatal sepsis are resistant to multiple antibiotics, including the World Health Organization-recommended empiric neonatal sepsis regimen of ampicillin/gentamicin. The Global Antibiotic Research and Development Partnership is aiming to develop alternative empiric antibiotic regimens that fulfil several criteria: (1) affordable in LMIC settings; (2) activity against neonatal bacterial pathogens, including extended-spectrum β-lactamase producers, gentamicin-resistant Gram-negative bacteria, and methicillin-resistant Staphylococcus aureus (MRSA); (3) a licence for neonatal use or extensive experience of use in neonates; and (4) minimal toxicities. In this review, we identify five antibiotics that fulfil these criteria: amikacin, tobramycin, fosfomycin, flomoxef, and cefepime. We describe the available characteristics of each in terms of mechanism of action, resistance mechanisms, clinical pharmacokinetics, pharmacodynamics, and toxicity profile. We also identify some knowledge gaps: (1) the neonatal pharmacokinetics of cefepime is reliant on relatively small and limited datasets, and the pharmacokinetics of flomoxef are also reliant on data from a limited demographic range and (2) for all reviewed agents, the pharmacodynamic index and target has not been definitively established for both bactericidal effect and emergence of resistance, with many assumed to have an identical index/target to similar class molecules. These five agents have the potential to be used in novel combination empiric regimens for neonatal sepsis. However, the data gaps need addressing by pharmacokinetic trials and pharmacodynamic characterisation.

Quantification and Explanation of the Variability of First-Dose Amikacin Concentrations in Critically Ill Patients Admitted to the Emergency Department: A Population Pharmacokinetic Analysis

BACKGROUND

There may be a difference between the determinants of amikacin exposure in emergency department (ED) versus intensive care (ICU) patients, and the peak amikacin concentration varies widely between patients. Moreover, when the first dose of antimicrobials is administered to septic patients admitted to the ED, fluid resuscitation and vasopressors have just been initiated. Nevertheless, population pharmacokinetic modelling data for amikacin in ED patients are unavailable.

OBJECTIVE

The aim of this study was to quantify the interindividual variability (IIV) in the pharmacokinetics of amikacin in patients admitted to the ED and to identify the patient characteristics that explain this IIV.

METHODS

Patients presenting at the ED with severe sepsis or septic shock were randomly assigned to receive amikacin 25 mg/kg or 15 mg/kg intravenously. Blood samples were collected at 1, 6 and 24 h after the onset of the first amikacin infusion. Data were analysed using nonlinear mixed-effects modelling.

RESULTS

A two-compartment population pharmacokinetic model was developed based on 279 amikacin concentrations from 97 patients. The IIV in clearance (CL) and central distribution volume (V₁) were 71% and 26%, respectively. Body mass index (BMI), serum total protein level, serum sodium level, and fluid balance 24 h after amikacin administration explained 30% of the IIV in V₁, leaving 18% of the IIV unexplained. BMI and creatinine clearance according to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation 24 h after amikacin administration explained 46% of the IIV in CL, and 39% remained unexplained.

CONCLUSION

The IIV of amikacin pharmacokinetics in ED patients is large. Higher doses may be considered in patients with low serum sodium levels, low total protein levels, or a high fluid balance.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT02365272.

Pharmacokinetic/pharmacodynamic evaluation of tobramycin dosing in critically ill patients: the Hartford nomogram does not fit

OBJECTIVES

Extended-interval dosing of tobramycin is widely applied in patients with the Hartford nomogram as a representative, while this dosing approach has not been extensively evaluated in critically ill patients. The goal of this study was to characterize the pharmacokinetics of tobramycin and to evaluate the appropriateness of the Hartford nomogram in critically ill patients.

METHODS

A retrospective analysis was performed based on a medical critical care database. The extracted concentration data of tobramycin were used for the construction of the population pharmacokinetic model using a non-linear mixed-effects modelling approach. Real-world data-based simulations were conducted to evaluate the pharmacodynamic target attainment (Cmax/MIC ≥10) and safety (concentration <0.5 mg/L for at least 4 h) of the Hartford nomogram.

RESULTS

A population pharmacokinetic model was built based on 307 measurements in 140 unique patients and externally validated by an independent study dataset. A two-compartment model was optimal for the structure model and creatinine clearance remained as the only covariate in the final model correlating to the clearance of tobramycin. Simulations indicated that the Hartford nomogram is effective for infections due to pathogens with an MIC of ≤1 mg/L, but not with an MIC of 2 mg/L. The percentage of patients who reached the non-toxicity target was quite low under the Hartford nomogram and a further extension of the dosing interval was necessary to minimize the toxicity.

CONCLUSIONS

The Hartford nomogram was not suitable for critically ill patients with pathogen MICs of 2 mg/L and drug monitoring is required to manage efficacy and toxicity.

Tobramycin Liquid Crystal Nanoparticles Eradicate Cystic Fibrosis-Related Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa biofilms cause persistent and chronic infections, most known clinically in cystic fibrosis (CF). Tobramycin (TOB) is a standard anti-pseudomonal antibiotic; however, in biofilm infections, its efficacy severely decreases due to limited permeability across the biofilm matrix. Herewith, a biomimetic, nanostructured, lipid liquid crystal nanoparticle-(LCNP)-formulation is discovered to significantly enhance the efficacy of TOB and eradicate P. aeruginosa biofilm infections. Using an advanced, biologically-relevant co-culture model of human CF bronchial epithelial cells infected with P. aeruginosa biofilms at an air-liquid interface, nebulized TOB-LCNPs completely eradicated 1 × 10⁹ CFU mL^-1 of P. aeruginosa after two doses, a 100-fold improvement over the unformulated antibiotic. The enhanced activity of TOB is not observed with a liposomal formulation of TOB or with ciprofloxacin, an antibiotic that readily penetrates biofilms. It is demonstrated that the unique nanostructure of the LCNPs drives the enhanced penetration of TOB across the biofilm barrier, but not through the healthy lung epithelium barrier, significantly increasing the available antibiotic concentration at the site of infection. The LCNPs are an innovative strategy to improve the performance of TOB as a directed pulmonary therapy, enabling the administration of lower doses, reducing the toxicity, and amplifying the anti-biofilm activity of the anti-pseudomonal antibiotic.

An international survey on aminoglycoside practices in critically ill patients: the AMINO III study

BACKGROUND

While aminoglycosides (AG) have been used for decades, debate remains on their optimal dosing strategy. We investigated the international practices of AG usage specifically regarding dosing and therapeutic drug monitoring (TDM) in critically ill patients. We conducted a prospective, multicentre, observational, cohort study in 59 intensive-care units (ICUs) in 5 countries enrolling all ICU patients receiving AG therapy for septic shock.

RESULTS

We enrolled 931 septic ICU patients [mean ± standard deviation, age 63 ± 15 years, female 364 (39%), median (IQR) SAPS II 51 (38-65)] receiving AG as part of empirical (761, 84%) or directed (147, 16%) therapy. The AG used was amikacin in 614 (66%), gentamicin in 303 (33%), and tobramycin in 14 (1%) patients. The median (IQR) duration of therapy was 2 (1-3) days, the number of doses was 2 (1-2), the median dose was 25 ± 6, 6 ± 2, and 6 ± 2 mg/kg for amikacin, gentamicin, and tobramycin respectively, and the median dosing interval was 26 (23.5-43.5) h. TDM of C_max and C_min was performed in 437 (47%) and 501 (57%) patients, respectively, after the first dose with 295 (68%) patients achieving a C_max/MIC > 8 and 353 (71%) having concentrations above C_min recommended thresholds. The ICU mortality rate was 27% with multivariable analysis showing no correlation between AG dosing or pharmacokinetic/pharmacodynamic target attainment and clinical outcomes.

CONCLUSION

Short courses of high AG doses are mainly used in ICU patients with septic shock, although wide variability in AG usage is reported. We could show no correlation between PK/PD target attainment and clinical outcome. Efforts to optimize the first AG dose remain necessary. Trial registration Clinical Trials, NCT02850029, registered on 29th July 2016, retrospectively registered, https://www.clinicaltrials.gov.

Population Pharmacokinetics Analysis of Amikacin Initial Dosing Regimen in Elderly Patients

There are limited data of amikacin pharmacokinetics (PK) in the elderly population. Hence, we aimed to describe the population PK of amikacin in elderly patients (>70 years old) and to establish optimized initial dosing regimens. We simulated individual maximum concentrations in plasma (Cmax) and minimal concentrations (Cmin) for several dosing regimens (200–2000 mg every 24, 48, and 72 h) for patients with creatinine clearance (CCr) of 10–90 mL/min and analyzed efficacy (Cmax/minimal inhibitory concentration (MIC) ≥ 8) for MICs of 4, 8, and 16 mg/L and safety (Cmin < 4 mg/L). A one-compartment model best described the data. CCr was the only covariate associated with amikacin clearance. The population PK parameter estimates were 2.25 L/h for clearance and 18.0 L for volume of distribution. Dosing simulations recommended the dosing regimens (1800 mg) with dosing intervals ranging 48–72 h for patients with CCr of 40–90 mL/min based on achievement of both efficacy for the MIC of 8 mg/L and safety. None of the dosing regimens achieved the targets for an MIC of 16 mg/L. We recommend the initial dosing regimen using a nomogram based on CCr for an MIC of ≤8 mg/L in elderly patients with CCr of 40–90 mL/min.

Antibiotics in Adult Cystic Fibrosis Patients: A Review of Population Pharmacokinetic Analyses

BACKGROUND

Lower respiratory tract infections are common in adult patients with cystic fibrosis (CF) and are frequently caused by Pseudomonas aeruginosa, resulting in chronic lung inflammation and fibrosis. The progression of multidrug-resistant strains of P. aeruginosa and alterations in the pharmacokinetics of many antibiotics in CF make optimal antimicrobial therapy a challenge, as reflected by high between- and inter-individual variability (IIV).

OBJECTIVES

This review provides a synthesis of population pharmacokinetic models for various antibiotics prescribed in adult CF patients, and aims at identifying the most reported structural models, covariates and sources of variability influencing the dose-concentration relationship.

METHODS

A literature search was conducted using the PubMed database, from inception to August 2020, and articles were retained if they met the inclusion/exclusion criteria.

RESULTS

A total of 19 articles were included in this review. One-, two- and three-compartment models were reported to best describe the pharmacokinetics of various antibiotics. The most common covariates were lean body mass and creatinine clearance. After covariate inclusion, the IIV (range) in total body clearance was 27.2% (10.40-59.7%) and 25.9% (18.0-33.9%) for β-lactams and aminoglycosides, respectively. IIV in total body clearance was estimated at 36.3% for linezolid and 22.4% for telavancin. The IIV (range) in volume of distribution was 29.4% (8.8-45.9%) and 15.2 (11.6-18.0%) for β-lactams and aminoglycosides, respectively, and 26.9% for telavancin. The median (range) of residual variability for all studies, using a combined (proportional and additive) model, was 12.7% (0.384-30.80%) and 0.126 mg/L (0.007-1.88 mg/L), respectively.

CONCLUSION

This is the first review that highlights key aspects of different population pharmacokinetic models of antibiotics prescribed in adult CF patients, effectively proposing relevant information for clinicians and researchers to optimize antibiotic therapy in CF.

A Prospective Clinical Study Characterizing the Influence of Morbid Obesity on the Pharmacokinetics of Gentamicin: Towards Individualized Dosing in Obese Patients

Background and Objective

Gentamicin is an aminoglycoside antibiotic predominantly used in bloodstream infections. Although the prevalence of obesity is increasing dramatically, there is no consensus on how to adjust the dose in obese individuals. In this prospective clinical study, we study the pharmacokinetics of gentamicin in morbidly obese and non-obese individuals to develop a dosing algorithm that results in adequate drug exposure across body weights.

Methods

Morbidly obese subjects undergoing bariatric surgery and non-obese healthy volunteers received one intravenous dose of gentamicin (obese: 5 mg/kg based on lean body weight, non-obese: 5 mg/kg based on total body weight [TBW]) with subsequent 24-h sampling. All individuals had a normal renal function. Statistical analysis, modelling and Monte Carlo simulations were performed using R version 3.4.4 and NONMEM^® version 7.3.

Results

A two-compartment model best described the data. TBW was the best predictor for both clearance [CL = 0.089 × (TBW/70)^0.73] and central volume of distribution [V_c = 11.9 × (TBW/70)^1.25] (both p < 0.001). Simulations showed how gentamicin exposure changes across the weight range with currently used dosing algorithms and illustrated that using a nomogram based on a ‘dose weight’ [70 × (TBW/70)^0.73] will lead to similar exposure across the entire population.

Conclusions

In this study in morbidly obese and non-obese individuals ranging from 53 to 221 kg we identified body weight as an important determinant for both gentamicin CL and V_c. Using a body weight-based dosing algorithm, optimized exposure across the entire population can be achieved, thereby potentially improving efficacy and safety of gentamicin in the obese and morbidly obese population.

Trial Registration

Registered in the Dutch Trial Registry (NTR6058).

Electronic supplementary material

The online version of this article (10.1007/s40262-019-00762-4) contains supplementary material, which is available to authorized users.

Antimicrobial Therapy in Septic Shock Is Conservative During Resuscitation and Maintenance Phases

Background: Maximal dosing of early antimicrobials with high loading and maintenance doses may optimize pharmacokinetic parameters to achieve and maintain therapeutic concentrations at the site of infection in septic shock. Little is known about the current practice of early antimicrobial dosing in septic shock. Objective: To characterize early antimicrobial dosing in patients in the resuscitation phase of septic shock. Methods: This retrospective cohort study included patients admitted to the medical intensive care unit (ICU) with septic shock. The primary outcome was the percentage of early antibiotic orders that were maximal or conservative during the resuscitation (0 to 48 hours) phase based on predefined dosing criteria. The secondary outcomes were the correlations of different dosing strategies on hospital length of stay (LOS), ICU LOS, and hospital mortality. Results: This study evaluated 161 patients and 692 antibiotic orders; 504 (72.8%) of the orders during the resuscitation phase were conservative. There were no differences in mortality (odds ratio = 0.66; 95% confidence interval = 0.35-1.25; P = .20), hospital LOS (median = 20 [interquartile range (IQR) = 10-34] vs 19 [IQR = 11-32] days; P = .93), or ICU LOS (median = 8 [IQR = 5-16] vs 9 [IQR = 5-15] days; P = .63) between maximal and conservative dosing groups, respectively, in the resuscitation phase. Limitations of this study included the use of institution-specific antimicrobial dosing guidelines and its retrospective nature. Conclusions: Early antibiotic dosing is conservative for a majority of patients in septic shock. Future studies are needed to evaluate the impact of dosing strategy on patient-centered outcomes in septic shock.

Monitoring of Tobramycin Exposure: What is the Best Estimation Method and Sampling Time for Clinical Practice?

OBJECTIVES

The objective of this article is to investigate the influence of blood sampling times on tobramycin exposure estimation and clinical decisions and to determine the best sampling times for two estimation methods used for therapeutic drug monitoring.

METHODS

Adult patients with cystic fibrosis, treated with once-daily intravenous tobramycin, were intensively sampled over one 24-h dosing interval to determine true exposure (AUC_0-24). The AUC_0-24s were then estimated using both log-linear regression and Bayesian forecasting methods for 21 different sampling time combinations. These were compared to true exposure using relative prediction errors. The differences in subsequent dose recommendations were calculated.

RESULTS

Twelve patients, with a median (range) age of 25 years (18-36) and weight of 66.5 kg (50.6-76.4) contributed 96 tobramycin concentrations. Five hundred and eighty-eight estimated AUC_0-24s were compared to 12 measured true AUC_0-24 values. Median relative prediction errors ranged from - 34.7 to 45.5% for the log-linear regression method and from - 14.46 to 11.23% for the Bayesian forecasting method across the 21 sampling combinations. The most unbiased exposure estimation was provided from concentrations sampled at 100/640 min after the start of the infusion using log-linear regression and at 70/160 min using Bayesian forecasting. Subsequent dosing recommendations varied greatly depending on the estimation method and the sampling times used.

CONCLUSION

Sampling times markedly influence bias in AUC_0-24 estimation, leading to greatly varied dose adjustments. The impact of blood sampling times on dosing decisions is reduced when using Bayesian forecasting.

Bacterial sepsis : Diagnostics and calculated antibiotic therapy

The mortality of patients with sepsis and septic shock is still unacceptably high. An effective calculated antibiotic treatment within 1 h of recognition of sepsis is an important target of sepsis treatment. Delays lead to an increase in mortality; therefore, structured treatment concepts form a rational foundation, taking relevant diagnostic and treatment steps into consideration. In addition to the assumed infection and individual risks of each patient, local resistance patterns and specific problem pathogens must be taken into account during the selection of anti-infective treatment. Many pathophysiologic alterations influence the pharmacokinetics (PK) of antibiotics during sepsis. The principle of standard dosing should be abandoned and replaced by an individual treatment approach with stronger weighting of the pharmacokinetics/pharmacodynamics (PK/PD) index of the substance groups. Although this is not yet the clinical standard, prolonged (or continuous) infusion of β‑lactam antibiotics and therapeutic drug monitoring (TDM) can help to achieve defined PK targets. Prolonged infusion is sufficient without TDM, but for continuous infusion, TDM is generally necessary. A further argument for individual PK/PD-oriented antibiotic approaches is the increasing number of infections due to multidrug-resistant (MDR) pathogens in the intensive care unit. For effective treatment, antibiotic stewardship teams (ABS teams) are becoming more established. Interdisciplinary cooperation of the ABS team with infectious disease (ID) specialists, microbiologists, and clinical pharmacists leads not only to rational administration of antibiotics, but also has a positive influence on treatment outcome. The gold standards for pathogen identification are still culture-based detection and microbiologic resistance testing for the various antibiotic groups. Despite the rapid investigation time, novel polymerase chain reaction(PCR)-based procedures for pathogen identification and resistance determination are currently only an adjunct to routine sepsis diagnostics, due to the limited number of studies, high costs, and limited availability. In complicated septic courses with multiple anti-infective therapies or recurrent sepsis, PCR-based procedures can be used in addition to treatment monitoring and diagnostics. Novel antibiotics represent potent alternatives in the treatment of MDR infections. Due to the often defined spectrum of pathogens and the practically (still) absent resistance, they are suitable for targeted treatment of severe MDR infections (therapy escalation). (Contribution available free of charge by "Free Access" [ https://link.springer.com/article/10.1007/s00101-017-0396-z ].).

PK/PD targets of amikacin and gentamicin in ICU patients

OBJECTIVES

We aimed to evaluate the probability to achieve PK-PD targets in patients with sepsis hospitalized in the intensive care unit (ICU) after a single dose of 30mg/kg of amikacin or 8mg/kg of gentamicin.

PATIENTS AND METHODS

This single-center prospective study included 138 ICU patients with severe sepsis or septic shock with an indication for intravenous amikacin (N=89) or gentamicin (N=49). Maximum concentration (C_max) was measured 30 minutes after infusion completion. PK/PD objectives were respectively C_max≥60mg/L and ≥30mg/L for amikacin and gentamicin for empirical therapy, and a C_max/MIC ratio≥8, as per French guidelines.

RESULTS

The median Simplified Acute Physiology Score II was 43 and ICU case fatality rate was 34.8%. A causative bacterial agent was identified in 94 patients (68.1%). Three pathogens had acquired aminoglycoside resistance and 15 were naturally resistant. The targeted C_max for the first dose was achieved in 53 patients (59.6%) receiving amikacin, and one (2.2%) patient receiving gentamicin. C_max/MIC ratio≥8 was obtained in all patients infected with susceptible pathogens (N=72). Factors associated with C_max≥60mg/L of amikacin in multivariate analysis were dose per kg of adapted body weight (OR=1.39, P<0.001) and renal clearance estimated with CKD-EPI formula (OR=0.98, P=0.003).

CONCLUSIONS

Despite high doses, amikacin and gentamicin first C_max remain dramatically low in ICU patients. However, an adequate C_max/MIC ratio was reached in all patients.

Rules of anti-infection therapy for sepsis and septic shock

Objective:

Sepsis is a deadly infection that causes injury to tissues and organs. Infection and anti-infective treatment are the eternal themes of sepsis. The successful control of infection is a key factor of resuscitation for sepsis and septic shock. This review examines evidence for the treatment of sepsis. This evidence is combined with clinical experiments to reveal the rules and a standard flowchart of anti-infection therapy for sepsis.

Data Sources:

We retrieved information from the PubMed database up to October 2018 using various search terms and their combinations, including sepsis, septic shock, infection, antibiotics, and anti-infection.

Study Selection:

We included data from peer-reviewed journals printed in English on the relationships between infections and antibiotics.

Results:

By combining the literature review and clinical experience, we propose a 6Rs rule for sepsis and septic shock management: right patients, right time, right target, right antibiotics, right dose, and right source control. This rule encompasses rational decisions regarding the timing of treatment, the identification of the correct pathogen, the selection of appropriate antibiotics, the formulation of a scientifically based antibiotic dosage regimen, and the adequate control of infectious foci.

Conclusions:

This review highlights how to recognize and treat sepsis and septic shock and provides rules and a standard flowchart for anti-infection therapy for sepsis and septic shock for use in the clinical setting.

[Bacterial sepsis : Diagnostics and calculated antibiotic therapy]

The mortality of patients with sepsis and septic shock is still unacceptably high. An effective antibiotic treatment within 1 h of recognition of sepsis is an important target of sepsis treatment. Delays lead to an increase in mortality; therefore, structured treatment concepts form a rational foundation, taking relevant diagnostic and treatment steps into consideration. In addition to the assumed focus and individual risks of each patient, local resistance patterns and specific problem pathogens must be taken into account for selection of anti-infection treatment. Many pathophysiological alterations influence the pharmacokinetics of antibiotics during sepsis. The principle of standard dosing should be abandoned and replaced by an individual treatment approach with stronger weighting of the pharmacokinetics/pharmacodynamics (PK/PD) index of the substance groups. Although this is not yet the clinical standard, prolonged (or continuous) infusion of beta-lactam antibiotics and therapeutic drug monitoring (TDM) can help to achieve defined PK targets. Prolonged infusion is sufficient without TDM but for continuous infusion TDM is basically necessary. A further argument for individual PK/PD-oriented antibiotic approaches is the increasing number of infections due to multidrug resistant pathogens (MDR) in the intensive care unit. For effective treatment antibiotic stewardship teams (ABS team) are becoming more established. Interdisciplinary cooperation of the ABS team with infectiologists, microbiologists and clinical pharmacists leads not only to a rational administration of antibiotics but also has a positive influence on the outcome. The gold standards for pathogen detection are still culture-based detection and microbiological resistance testing for the various antibiotic groups. Despite the rapid investigation time, novel polymerase chain reaction (PCR)-based procedures for pathogen identification and resistance determination, are currently only an adjunct to routine sepsis diagnostics due to the limited number of studies, high costs and limited availability. In complicated septic courses with multiple anti-infective treatment or recurrent sepsis, PCR-based procedures can be used in addition to therapy monitoring and diagnostics. Novel antibiotics represent potent alternatives in the treatment of MDR infections. Due to the often defined spectrum of pathogens and the practically absent resistance, they are suitable for targeted treatment of severe MDR infections (therapy escalation).

New paradigm for rapid achievement of appropriate therapy in special populations: coupling antibiotic dose optimization rapid microbiological methods

INTRODUCTION

Some special patient populations (e.g. critically ill, burns, hematological malignancy, post-major surgery, post-major trauma) have characteristics that lead to higher rates of failure and mortality associated with infection. Choice of effective antibiotics and optimized doses are challenging in these patients that are commonly infected by multidrug-resistant pathogens. Areas covered: A review of the importance of diagnosis and the place of newer microbiological methods (e.g. whole-genome sequencing) to ensure rapid transition from empiric to directed antibiotic therapy is provided. The effects of pathophysiological changes on antibiotic pharmacokinetics are also provided. Expert opinion: Product information dosing regimens do not address the pharmacokinetic alterations that can occur in special patient populations and increase the likelihood of therapeutic failure and the emergence of bacterial resistance. Altered dosing approaches, supplemented with the use of dosing software and therapeutic drug monitoring, may be needed to ensure optimal antibiotic exposure and better therapeutic outcomes in these patients with severe infection. Dose optimization needs to be coupled with advanced microbiological techniques that enable rapid microbiological identification and characterization of resistance mechanism to ensure that maximally effective directed therapy can be chosen.

Optimizing Amikacin Dosage in Pediatrics Based on Population Pharmacokinetic/Pharmacodynamic Modeling

OBJECTIVE

Our objective was to determine the population pharmacokinetic parameters of amikacin in pediatric patients to contribute to the future development of a revised optimum dose and population-specific dosing regimens.

METHODS

We performed a retrospective chart review in non-critical pediatric patients (aged 1-12 years) who received amikacin for suspected or proven Gram-negative infection at a university hospital. The population pharmacokinetic models were developed using Monolix 4.4. Pharmacokinetic/pharmacodynamic (PK/PD) simulations were performed to explore the ability of different dosage regimens to achieve the pharmacodynamic targets.

RESULTS

The analysis included 134 amikacin plasma concentrations from 67 patients with a mean ± standard deviation age of 4.1 ± 3.9 years and bodyweight of 15 ± 8.4 kg. The patients received an amikacin total daily dose (TDD) of 23 ± 7.3 mg/kg, which resulted in peak and trough concentrations of 20.65 ± 7.6 and 2.4 ± 1.7 mg/l, respectively. The estimated pharmacokinetic parameters for amikacin were 1.2 l/h and 6.5 l for total body clearance (CL) and the volume of distribution (V), respectively. Dosing simulations showed that the standard dosing regimen (15 mg/kg/day) of amikacin achieved the PK/PD target of peak serum concentration (C_peak)/minimum inhibitory concentration (MIC) ≥ 8 for an MIC of 2 mg/l; higher doses were required to achieve higher MIC values.

CONCLUSION

The simulation results indicated that amikacin 20 mg/kg once daily provided a higher probability of target attainment with lower toxicity than dosing three times daily. In addition, combination therapy is recommended for pathogens with an MIC of ≥ 8 mg/l.

Effect of hypothermia treatment on gentamicin pharmacokinetics in neonates with hypoxic-ischaemic encephalopathy: A systematic review and meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Hypothermia is the current standard therapy for asphyxiated neonates with hypoxic-ischaemic encephalopathy (HIE). Gentamicin is used for the empirical treatment of early-onset neonatal sepsis. We investigated the influence of hypothermia treatment on gentamicin pharmacokinetics and suggested the appropriate dosing recommendations for gentamicin in neonates with HIE receiving hypothermia treatment.

METHODS

We searched studies published until February 2017 in MEDLINE using PubMed, EMBASE and the Cochrane Library. Three independent reviewers screened the literature and extracted data from each study. All of the studies that reported the blood concentrations or pharmacokinetic parameters of gentamicin in hypothermic neonates with HIE were included in this review. Articles were excluded if they were not original research.

RESULT AND DISCUSSION

A total of 8 observational studies met the inclusion criteria. Meta-analyses were performed in which the mean difference of gentamicin for the trough concentration and clearance between hypothermic and normothermic neonates were 0.81 mg/L (95% confidence interval [-0.07, 1.69]) and -0.21 mL/kg/min (95% confidence interval [-0.31, -0.12]), respectively. The factors affecting gentamicin clearance in hypothermic neonates with HIE were gestational age, birthweight and serum creatinine.

WHAT IS NEW AND CONCLUSION

Gentamicin clearance is decreased in neonates with HIE receiving hypothermia treatment compared to those not receiving hypothermia treatment. Modified gentamicin dosing regimens are required to avoid potential toxicity related to higher concentrations during hypothermia treatment.

Evaluation of Epithelial Lining Fluid Concentration of Amikacin in Critically Ill Patients With Ventilator-Associated Pneumonia

INTRODUCTION

Classically, aminoglycosides are known to have low penetration into the lung tissue. So far, no study has been conducted on human adult patients to evaluate amikacin concentration in epithelial lining fluid (ELF) of the alveoli. Therefore, convincing data are not available from the perspective of pharmacokinetics to support the fact that a dosage of 20 mg/kg of amikacin is sufficient to treat patients with ventilator-associated pneumonia (VAP).

METHOD

This was a pilot study of amikacin concentration measurement in the alveolar site of action in critically ill adult patients with VAP who required aminoglycoside therapy. A dose of 20 mg/kg of amikacin was administered over a 30-minute infusion. The serum concentrations of amikacin were evaluated in the first, second, fourth, and sixth hours. However, the ELF concentration of amikacin was evaluated in the second hour with the help of bronchoalveolar lavage sampling technique.

RESULTS

A total number of 8 patients was included in the study. The mean (SD) administered dose was 20 (0.9) mg/kg. The mean (SD) peak plasma concentration of amikacin was 59.6 (23) mg/L, with the volume of distribution of 0.36 (0.13)L/kg. The amikacin concentration in ELF was successfully measured in 7 patients (6.3) mg/L. The lung tissue penetration of the drug was described as alveolar percentage, proportional to both the first- and second-hour plasma concentrations, with a mean (SD) of 10.1% (8.4%) and 18% (16.7%), respectively.

CONCLUSION

To our knowledge, the current study is the first that investigates whether standard doses of amikacin may lead to sufficient alveolar concentration of the drug. The results show that administration of amikacin in doses of 20 mg/kg in critically ill patients with VAP may not provide sufficient concentrations in ELF.

High-dose amikacin for achieving serum target levels in critically ill elderly patients

Introduction

To achieve target concentrations, the application of higher-than-standard doses of amikacin is proposed for the treatment of sepsis due to an increase in volume of distribution and clearance, but little data are available on aminoglycoside administration in critically ill elderly patients.

Patients and methods

Forty critically ill elderly patients (aged over 65 years) who required amikacin therapy due to severe documented, or suspected gram-negative infections, were randomly assigned to two treatment groups. Group A (20 patients) received 15 mg/kg amikacin and Group B (20 patients) received 25 mg/kg amikacin per day as a single daily dose. All the patients were monitored for renal damage by the daily monitoring of serum creatinine. The amikacin peak (C_max) and trough (C_min) serum concentrations were measured on Days 3 and 7 postadministration.

Results

Data from 18 patients in Group A and 15 patients in Group B were finally analyzed. On Day 3, the amikacin mean C_max levels in the standard and high-dose treatment groups were 30.4±11 and 52.3±16.1 µg/mL (P<0.001), and the C_min levels were 3.2±2.1 and 5.2±2.8 µg/mL, respectively (P=0.035). On Day 7, the C_max levels in the standard and high-dose groups were 33±7.3 and 60.0±17.6 µg/mL (P=0.001), and the C_min levels were 3.2±2.9 and 9.3±5.6 µg/mL, respectively (P=0.002). In only six (40%) of the patients in the high-dose groups and none of the patients in the standard-dose group, amikacin C_max reached the target levels (>64 µg/mL), whereas the amikacin mean C_min levels in the high-dose group were above the threshold of toxicity (5 µg/mL).

Conclusion

Our results suggest that the optimum dose of amikacin should be determined for elderly critically ill patients. It seems that higher-than-standard doses of amikacin with more extended intervals might be more appropriate than standard once-daily dosing in the elderly critically ill patients.

Population pharmacokinetic modelling, Monte Carlo simulation and semi-mechanistic pharmacodynamic modelling as tools to personalize gentamicin therapy

Population pharmacokinetic modelling, Monte Carlo simulation and semi-mechanistic pharmacodynamic modelling are all tools that can be applied to personalize gentamicin therapy. This review summarizes and evaluates literature knowledge on the population pharmacokinetics and pharmacodynamics of gentamicin and identifies areas where further research is required to successfully individualize gentamicin therapy using modelling and simulation techniques. Thirty-five studies have developed a population pharmacokinetic model of gentamicin and 15 studies have made dosing recommendations based on Monte Carlo simulation. Variability in gentamicin clearance was most commonly related to renal function in adults and body weight and age in paediatrics. Nine studies have related aminoglycoside exposure indices to clinical outcomes. Most commonly, efficacy has been linked to a Cmax/MIC ≥7-10 and a AUC24/MIC ≥70-100. No study to date has shown a relationship between predicted achievement of exposure targets and actual clinical success. Five studies have developed a semi-mechanistic pharmacokinetic/pharmacodynamic model to predict bacteria killing and regrowth following gentamicin exposure and one study has developed a deterministic model of aminoglycoside nephrotoxicity. More complex semi-mechanistic models are required that consider the immune response, use of multiple antibiotics, the severity of illness, and both efficacy and toxicity. As our understanding grows, dosing of gentamicin based on sound pharmacokinetic/pharmacodynamic principles should be applied more commonly in clinical practice.

Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016

OBJECTIVE

To provide an update to "Surviving Sepsis Campaign Guidelines for Management of Sepsis and Septic Shock: 2012."

DESIGN

A consensus committee of 55 international experts representing 25 international organizations was convened. Nominal groups were assembled at key international meetings (for those committee members attending the conference). A formal conflict-of-interest (COI) policy was developed at the onset of the process and enforced throughout. A stand-alone meeting was held for all panel members in December 2015. Teleconferences and electronic-based discussion among subgroups and among the entire committee served as an integral part of the development.

METHODS

The panel consisted of five sections: hemodynamics, infection, adjunctive therapies, metabolic, and ventilation. Population, intervention, comparison, and outcomes (PICO) questions were reviewed and updated as needed, and evidence profiles were generated. Each subgroup generated a list of questions, searched for best available evidence, and then followed the principles of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system to assess the quality of evidence from high to very low, and to formulate recommendations as strong or weak, or best practice statement when applicable.

RESULTS

The Surviving Sepsis Guideline panel provided 93 statements on early management and resuscitation of patients with sepsis or septic shock. Overall, 32 were strong recommendations, 39 were weak recommendations, and 18 were best-practice statements. No recommendation was provided for four questions.

CONCLUSIONS

Substantial agreement exists among a large cohort of international experts regarding many strong recommendations for the best care of patients with sepsis. Although a significant number of aspects of care have relatively weak support, evidence-based recommendations regarding the acute management of sepsis and septic shock are the foundation of improved outcomes for these critically ill patients with high mortality.

Pediatric Obesity: Pharmacokinetic Alterations and Effects on Antimicrobial Dosing

Limited data exist for appropriate drug dosing in obese children. This comprehensive review summarizes pharmacokinetic (PK) alterations that occur with age and obesity, and these effects on antimicrobial dosing. A thorough comparison of different measures of body weight and specific antimicrobial agents including cefazolin, cefepime, ceftazidime, daptomycin, doripenem, gentamicin, linezolid, meropenem, piperacillin-tazobactam, tobramycin, vancomycin, and voriconazole is presented. PubMed (1966-July 2015) and Cochrane Library searches were performed using these key terms: children, pharmacokinetic, obesity, overweight, body mass index, ideal body weight, lean body weight, body composition, and specific antimicrobial drugs. PK studies in obese children and, if necessary, data from adult studies were summarized. Knowledge of PK alterations stemming from physiologic changes that occur with age from the neonate to adolescent, as well as those that result from increased body fat, become an essential first step toward optimizing drug dosing in obese children. Excessive amounts of adipose tissue contribute significantly to body size, total body water content, and organ size and function that may modify drug distribution and clearance. PK studies that evaluated antimicrobial dosing primarily used total (or actual) body weight (TBW) for loading doses and TBW or adjusted body weight for maintenance doses, depending on the drugs' properties and dosing units. PK studies in obese children are imperative to elucidate drug distribution, clearance, and, consequently, the dose required for effective therapy in these children. Future studies should evaluate the effects of both age and obesity on drug dosing because the incidence of obesity is increasing in pediatric patients.

Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016

OBJECTIVE

To provide an update to "Surviving Sepsis Campaign Guidelines for Management of Sepsis and Septic Shock: 2012".

DESIGN

A consensus committee of 55 international experts representing 25 international organizations was convened. Nominal groups were assembled at key international meetings (for those committee members attending the conference). A formal conflict-of-interest (COI) policy was developed at the onset of the process and enforced throughout. A stand-alone meeting was held for all panel members in December 2015. Teleconferences and electronic-based discussion among subgroups and among the entire committee served as an integral part of the development.

METHODS

The panel consisted of five sections: hemodynamics, infection, adjunctive therapies, metabolic, and ventilation. Population, intervention, comparison, and outcomes (PICO) questions were reviewed and updated as needed, and evidence profiles were generated. Each subgroup generated a list of questions, searched for best available evidence, and then followed the principles of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system to assess the quality of evidence from high to very low, and to formulate recommendations as strong or weak, or best practice statement when applicable.

RESULTS

The Surviving Sepsis Guideline panel provided 93 statements on early management and resuscitation of patients with sepsis or septic shock. Overall, 32 were strong recommendations, 39 were weak recommendations, and 18 were best-practice statements. No recommendation was provided for four questions.

CONCLUSIONS

Substantial agreement exists among a large cohort of international experts regarding many strong recommendations for the best care of patients with sepsis. Although a significant number of aspects of care have relatively weak support, evidence-based recommendations regarding the acute management of sepsis and septic shock are the foundation of improved outcomes for these critically ill patients with high mortality.

Extended-Interval Dosing of Aminoglycoside Antibiotics in Critically Ill Patients

Although aminoglycosides remain an essential part of therapy of severe gram-negative infections in critically ill patients, the use of extended-interval aminoglycoside dosing (EIAD) in this population is highly controversial. The rationale for EIAD is based on major pharmacodynamic characteristics of the aminoglycosides, which include concentration-dependent bactericidal effects, postantibiotic effect, and adaptive resistance. Alterations in the pharmacokinetics of aminoglycosides in the critically ill have been well documented, including changes in both drug distribution and elimination. These pharmacokinetic alterations may prevent critically ill patients from realizing the potential benefits of EIAD by reducing serum concentrations achieved by recommended EIAD regimens and may perhaps place patients at risk of therapeutic failure. Although numerous studies of EIAD have been conducted, there is a lack of data specifically concerning the efficacy and safety of EIAD in the critically ill. The most appropriate methods for monitoring EIAD in this population are also not clearly established. There are thus many questions regarding the suitability of EIAD in the critically ill. This article briefly reviews the rationale for EIAD and data related to the pharmacokinetics, efficacy, safety, and clinical monitoring of EIAD in critically ill patients. Considerations and recommendations for use of EIAD in the critically ill are provided.

Gentamicin Pharmacokinetics in Elderly Patients with Normal Renal Function

Objective:

To establish the pharmacokinetic parameters of gentamicin in elderly patients and to compare predicted concentrations based on the Dettli method, with actual concentrations.

Design:

Measurement of gentamicin concentrations and pharmacokinetic parameters in a consecutive patient sample with comparison to ones predicted by the Dettli method.

Setting:

Medical and surgical units in a Veterans Affairs Medical Center.

Patients:

Forty-six consecutive elderly men treated with gentamicin for documented or presumed infection and had stable, normal renal function.

Main Outcome Measures:

The following information was calculated or measured: elimination rate constant (kel), elimination half-life, volume of distribution (Vd), and peak and trough concentrations.

Results:

The mean kel (0.16 ± 0.05 h−1) was not significantly different (p=0.2) from the Dettli method prediction, and the mean Vd (0.36 ± 0.1 L/kg) was 37 percent higher than that usually reported. Actual peak and trough concentrations were significantly lower (both p<0.01) than predicted concentrations.

Conclusions:

Based on our findings, higher than recommended loading doses and longer dosage intervals may be required in the elderly. The Dettli method is useful to estimate kel in the elderly.

Influence of Renal Replacement Modalities on Amikacin Population Pharmacokinetics in Critically Ill Patients on Continuous Renal Replacement Therapy

The objective of this study was to describe amikacin pharmacokinetics (PK) in critically ill patients receiving equal doses (30 ml/kg of body weight/h) of continuous venovenous hemofiltration (CVVH) and continuous venovenous hemodiafiltration (CVVHDF). Patients receiving amikacin and undergoing CVVH or CVVHDF were eligible. Population pharmacokinetic analysis and Monte Carlo simulation were undertaken using the Pmetrics software package for R. Sixteen patients (9 undergoing CVVH, 11 undergoing CVVHDF) and 20 sampling intervals were analyzed. A two-compartment linear model best described the data. Patient weight was the only covariate that was associated with drug clearance. The mean ± standard deviation parameter estimates were 25.2 ± 17.3 liters for the central volume, 0.89 ± 1.17 h(-1) for the rate constant for the drug distribution from the central to the peripheral compartment, 2.38 ± 6.60 h(-1) for the rate constant for the drug distribution from the peripheral to the central compartment, 4.45 ± 2.35 liters/h for hemodiafiltration clearance, and 4.69 ± 2.42 liters/h for hemofiltration clearance. Dosing simulations for amikacin supported the use of high dosing regimens (≥25 mg/kg) and extended intervals (36 to 48 h) for most patients when considering PK/pharmacodynamic (PD) targets of a maximum concentration in plasma (Cmax)/MIC ratio of ≥8 and a minimal concentration of ≤2.5 mg/liter at the end of the dosing interval. The mean clearance of amikacin was 1.8 ± 1.3 liters/h by CVVHDF and 1.3 ± 1 liters/h by CVVH. On the basis of simulations, a strategy of an extended-interval high loading dose of amikacin (25 mg/kg every 48 h) associated with therapeutic drug monitoring (TDM) should be the preferred approach for aminoglycoside treatment in critically ill patients receiving continuous renal replacement therapy (CRRT). (This study is a substudy of a trial registered at ClinicalTrials.gov under number NCT01403220.).

Pharmacodynamic Properties of Antibiotics: Application to Drug Monitoring and Dosage Regimen Design

The goal of antimicrobial chemotherapy is to effectively eradicate pathogenic organisms while minimizing the likelihood of drug-related adverse effects. In this era of cost containment, consideration should also be given to performing this task with the smallest total dose of drug and the shortest duration of therapy. Determination of the appropriate dose and dosing interval of an antimicrobial requires knowledge and integration of both its pharmacokinetic and pharmacodynamic properties.

Assessing Predictive Performance of Published Population Pharmacokinetic Models of Intravenous Tobramycin in Pediatric Patients

Several population pharmacokinetic models describe the dose-exposure relationship of tobramycin in pediatric patients. Before the implementation of these models in clinical practice for dosage adjustment, their predictive performance should be externally evaluated. This study tested the predictive performance of all published population pharmacokinetic models of tobramycin developed for pediatric patients with an independent patient cohort. A literature search was conducted to identify suitable models for testing. Demographic and pharmacokinetic data were collected retrospectively from the medical records of pediatric patients who had received intravenous tobramycin. Tobramycin exposure was predicted from each model. Predictive performance was assessed by visual comparison of predictions to observations, by calculation of bias and imprecision, and through the use of simulation-based diagnostics. Eight population pharmacokinetic models were identified. A total of 269 concentration-time points from 41 pediatric patients with cystic fibrosis were collected for external evaluation. Three models consistently performed best in all evaluations and had mean errors ranging from -0.4 to 1.8 mg/liter, relative mean errors ranging from 4.9 to 29.4%, and root mean square errors ranging from 47.8 to 66.9%. Simulation-based diagnostics supported these findings. Models that allowed a two-compartment disposition generally had better predictive performance than those that used a one-compartment disposition model. Several published models of the pharmacokinetics of tobramycin showed reasonable low levels of bias, although all models seemed to have some problems with imprecision. This suggests that knowledge of typical pharmacokinetic behavior and patient covariate values alone without feedback concentration measurements from individual patients is not sufficient to make precise predictions.

Aminoglycoside-induced nephrotoxicity

Aminoglycosides are among the oldest antibiotics available to treat serious infections caused by primarily, Gram-negative bacteria. The most commonly utilized parenteral agents in this class include gentamicin, tobramycin and amikacin. Aminoglycosides are concentration-dependent, bactericidal agents that undergo active transport into the cell where they inhibit protein synthesis on the 30S subunit of the bacterial ribosome. As the use of aminoglycosides became more widespread, the toxic effects of these agents, most notably ototoxicity and nephrotoxicity, became more apparent. When other, safer, antimicrobial agents became available, the use of aminoglycosides sharply declined. The development of multi-drug resistance among bacteria has now lead clinicians to reexamine the role of the aminoglycosides in the treatment of serious infections. This review will revisit the mechanism and risk factors for the development of aminoglycoside-induced nephrotoxicity, as well as strategies to prevent patients from developing nephrotoxicity.

Outcomes of a new dosage regimen of amikacin based on pharmacokinetic parameters of Korean neonates

PURPOSE

Study results indicating improved neonatal amikacin therapy outcomes through the use of a dosage regimen tailored to population-specific pharmacokinetic parameters are presented.

METHODS

In a retrospective analysis, outcomes of amikacin therapy were evaluated in two groups of Korean neonates: group 1 (n = 107), who received amikacin according to standard neonatal dosing recommendations and empirical dosing guidelines, which often resulted in a need for dosage adjustments; and group 2 (n = 74), who were treated under a revised dosage regimen derived from pharmacokinetic data on group 1 and taking into account unusually high interpatient variability in amikacin clearance among Korean newborns relative to Caucasian populations. The influences of postconceptional and postnatal age on amikacin pharmacokinetics were also evaluated.

RESULTS

Relative to standard and empirical amikacin dosing, the revised dosage regimen resulted in a significantly higher percentage of neonates achieving peak concentrations within the target range of 20-30 mg/L (81.3% in group 2 versus 50.7% in group 1, p < 0.001). The percentage of neonates with a peak concentration of <20 mg/L was significantly lower in group 2 (3.8%) versus group 1 (21.6%, p < 0.001), as were the proportion of neonates with peak concentrations of >30 mg/L (15.0% versus 27.6%, p < 0.001) and the need for dosage adjustment by a pharmacist (31.6% versus 59.7%, p = 0.056).

CONCLUSION

A new amikacin dosing regimen based on the pharmacokinetic parameters of Korean neonates was effective in achieving peak and trough amikacin concentrations within the target range.

Bayesian pharmacokinetic analysis of a gentamicin nomogram in neonates: a retrospective study

BACKGROUND

Although gentamicin is used extensively within the first week of life for suspected sepsis in neonates, little is known about the performance of gentamicin dosing nomograms in this population.

OBJECTIVE

The goal of our study was to retrospectively assess the performance of a gentamicin dosing nomogram in neonates given gentamicin during the first week after birth.

METHODS

In this retrospective study, gentamicin therapeutic drug monitoring data were collected during routine clinical care for all neonates who were born in St. Boniface General Hospital (Winnipeg, Manitoba, Canada) between January 1999 and April 2001 and given gentamicin during the first week after birth. We used Bayesian pharmacokinetic analysis to retrospectively assess the performance of our gentamicin dosing nomogram in neonates born at gestation ages <32 weeks, between 32 and 34 weeks, and >34 weeks. Bayesian pharmacokinetic values for parameters within groups were compared and used to explore predicted peak and trough serum gentamicin concentrations based on the institutional dosing nomogram.

RESULTS

In a total of 58 neonates, those neonates born at ≤34 weeks' gestation had a weight-normalized apparent volume of gentamicin distribution 1.6 times larger than infants born after 34 weeks' gestation (P<0.001), as identified by Bayesian analysis. Weight-normalized gentamicin clearance was 22% lower in the youngest age category (P<0.01). Only 33% of predicted peak serum gentamicin concentrations were >6 mg/L for neonates born at ≤34 weeks' gestation, whereas 90% were therapeutic in neonates born at >34 weeks' gestation (P<0.001). With the present nomogram, the likelihood of an indication for adjustment of the dosing regimen was 12.4-fold higher (95% CI, 3.5-43.7) for those neonates born at ≤34 weeks' gestation.

CONCLUSIONS

These results have important clinical implications with regard to the advisability of determining peak serum gentamicin concentrations in neonates born at ≤34 weeks' gestation. Sampling of peak serum concentrations is indicated in this population to avoid underdosing and potential loss of therapeutic efficacy.

Antimicrobial treatment of febrile neutropenia: pharmacokinetic-pharmacodynamic considerations

Patients with cancer or hematologic diseases are particularly at risk of infection leading to high morbidity, mortality and costs. Extensive data show that optimization of the administration of antimicrobials according to their pharmacokinetic and pharmacodynamic parameters improves clinical outcome. Evidence is growing that when pharmacokinetic and pharmacodynamic parameters are used to target not only clinical cure but also eradication, the selection resistance is also contained. This is of particular importance in patients with neutropenia in whom increasing rates of drug-resistant Gram-negative bacteria have been reported, particularly Pseudomonas aeruginosa. Based on experimental and clinical studies, pharmacokinetic and pharmacodynamic parameters are discussed in this review for each antibiotic used in febrile neutropenia in order to help physicians improve dosing and optimization of antimicrobial agents.

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.

Clinical pharmacist impact on care, length of stay, and cost in pediatric cystic fibrosis (CF) patients

BACKGROUND

Cystic fibrosis (CF) patients are often treated with aminoglycoside (AG) antibiotics during infective pulmonary exacerbations. Achieving pharmacokinetic and pharmacodynamic (PK/PD) targets to improve outcomes and counteract resistance is paramount.

PURPOSE

The primary objective was to compare the number of pediatric CF patients achieving AG PK/PD targets when a clinical pharmacist (CP) managed therapeutic drug monitoring (TDM) compared with usual care (UC).

METHODS

A retrospective cohort study was conducted on the records of 40 CF patients that received AGs and ≥2 serum samples between 1/2007 and 5/2009. Chi-square and Student's t-test were used to analyze nominal and continuous variables, respectively.

RESULTS

Twenty-nine patients with 52 courses of AGs were included the CP group, and 22 patients with 42 courses were included the UC group. Ninety-eight percent of patients in the CP group reached AG PK/PD targets compared with 71% in the UC group, P < 0.001. Patients in the CP group reached the AG PK/PD target in a mean of 1.9 ± 0.8 days compared with 4.8 ± 3.4 days in the UC group, P < 0.0001. The average LOS in the CP group was 9 ± 5 days compared with 12 ± 7.5 days in the UC group, P = 0.033. The mean number of levels per patient was 2.7 in the CP group compared with 5.2 (range of 2-20) in the UC group, P < 0.001. Resource utilization associated with drug levels, dosing adjustments and LOS were $26,549, $14,069, and $1,680,000 in the CP group as compared with $40,683, $27,812, and $1,940,000, respectively, in the UC group.

CONCLUSION

CP managed TDM resulted in a significantly higher percentage of pediatric CF patients achieving AG PK/PD targets 3 days sooner with an average LOS that was 3 days shorter. CP managed TDM resulted in significantly fewer dosage adjustments, drug levels, and cost associated with serum sampling, drug wastage, and LOS.