Is a randomized trial of a short course of aminoglycoside added to β-lactam antibiotics for empirical treatment in critically ill patients with sepsis justified?

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.

Evaluation of aminoglycosides utilization in intensive care units of a teaching hospital in southern Iran

Background:

Inappropriate use of antimicrobial agents is one of the most important factors in inducing resistance and prolonged hospitalization as well as increase in patient mortality rate.

Objective:

The aim of this study was to evaluate aminoglycosides (AGs) usage pattern at intensive care units (ICUs) of Nemazee hospital Shiraz, Iran.

Methods:

In this cross-sectional study, the usage pattern of AGs was evaluated during 32 months. Guidelines for AGs usage were approved by the drug and therapeutic committee of the hospital, and criteria were developed to assess 11 parameters involving AGs therapy, such as proper indication for the use of the drug, dosage and duration of therapy. Clinical parameters, such as microbial culture and sensitivity, serum creatinine (SCr) and creatinine clearance, and white blood cell count were evaluated.

Results:

Ninety-five patients were recruited, 50 male and 45 females. In most patients (64%) the origin of infection was hospital and only in 36% of them, community was the source. Ventilator associated pneumonia (27%), central nervous system (25%) and urinary tract infection (10%) were the most important indications for AGs prescription. Scores of AGs usage at Nemazee hospital was calculated as 5.9 out of 11, which meant that in only 54% of cases AGs prescription was based on guideline proposed by the Department of Clinical Pharmacy of Nemazee Hospital.

Conclusions:

Non-adherence to the guidelines occurred frequently in the ICUs of Nemazee hospital. Prescription of loading dose, and AGs level measurement were not done and evaluating microbiological data was often neglected. Incorporating pharmacists in the health care team and holding training programs for physicians and nurses with the goal of raising awareness about the proposed guideline.

Individualising Therapy to Minimize Bacterial Multidrug Resistance

The scourge of antibiotic resistance threatens modern healthcare delivery. A contributing factor to this significant issue may be antibiotic dosing, whereby standard antibiotic regimens are unable to suppress the emergence of antibiotic resistance. This article aims to review the role of pharmacokinetic and pharmacodynamic (PK/PD) measures for optimising antibiotic therapy to minimise resistance emergence. It also seeks to describe the utility of combination antibiotic therapy for suppression of resistance and summarise the role of biomarkers in individualising antibiotic therapy. Scientific journals indexed in PubMed and Web of Science were searched to identify relevant articles and summarise existing evidence. Studies suggest that optimising antibiotic dosing to attain defined PK/PD ratios may limit the emergence of resistance. A maximum aminoglycoside concentration to minimum inhibitory concentration (MIC) ratio of > 20, a fluoroquinolone area under the concentration-time curve to MIC ratio of > 285 and a β-lactam trough concentration of > 6 × MIC are likely required for resistance suppression. In vitro studies demonstrate a clear advantage for some antibiotic combinations. However, clinical evidence is limited, suggesting that the use of combination regimens should be assessed on an individual patient basis. Biomarkers, such as procalcitonin, may help to individualise and reduce the duration of antibiotic treatment, which may minimise antibiotic resistance emergence during therapy. Future studies should translate laboratory-based studies into clinical trials and validate the appropriate clinical PK/PD predictors required for resistance suppression in vivo. Other adjunct strategies, such as biomarker-guided therapy or the use of antibiotic combinations require further investigation.