Microneedle Aptamer-Based Sensors for Continuous, Real-Time Therapeutic Drug Monitoring

The ability to continuously monitor the concentration of specific molecules in the body is a long-sought goal of biomedical research. For this purpose, interstitial fluid (ISF) was proposed as the ideal target biofluid because its composition can rapidly equilibrate with that of systemic blood, allowing the assessment of molecular concentrations that reflect full-body physiology. In the past, continuous monitoring in ISF was enabled by microneedle sensor arrays. Yet, benchmark microneedle sensors can only detect molecules that undergo redox reactions, which limits the ability to sense metabolites, biomarkers, and therapeutics that are not redox-active. To overcome this barrier, here, we expand the scope of these devices by demonstrating the first use of microneedle-supported electrochemical, aptamer-based (E-AB) sensors. This platform achieves molecular recognition based on affinity interactions, vastly expanding the scope of molecules that can be sensed. We report the fabrication of microneedle E-AB sensor arrays and a method to regenerate them for multiple uses. In addition, we demonstrate continuous molecular measurements using these sensors in flow systems in vitro using single and multiplexed microneedle array configurations. Translation of the platform to in vivo measurements is possible as we demonstrate with a first E-AB measurement in the ISF of a rodent. The encouraging results reported in this work should serve as the basis for future translation of microneedle E-AB sensor arrays to biomedical research in preclinical animal models.

Ensuring target concentrations of antibiotics in critically ill patients through dose adjustment

INTRODUCTION

Antibiotics are commonly prescribed in critical care, and given the large variability of pharmacokinetic (PK) parameters in these patients, drug PK frequently varies during therapy with the risk of either treatment failure or toxicity. Therefore, adequate antibiotic dosing in critically ill patients is very important.

AREAS COVERED

This review provides an overview of the basic principles of PK and pharmacodynamics of antibiotics and the main patient and pathogen characteristics that may affect the dosage of antibiotics and different approaches to adjust doses.

EXPERT OPINION

Dose adjustment should be done for aminoglycosides and glycopeptides based on daily drug concentration monitoring. For glycopeptides, in particular vancomycin, the residual concentration (Cres) should be assessed daily. For beta-lactam antibiotics, a loading dose should be administered, followed by three different possible approaches, as TDM is rarely available in most centers: 1) antibiotic regimens should be adapted according to renal function and other risk factors; 2) nomograms or software can be used to calculate daily dosing; 3) TDM should be performed 24-48 h after the initiation of treatment; however, the results are required within 24 hours to appropriately adjust dosage regimens. Drug dosing should be reduced or increased according to the TDM results.

OUP accepted manuscript

Background

Dosing regimens guided by therapeutic drug monitoring (TDM) may be able to improve penicillin exposure in patients, which could result in improved patient health outcomes.

Objectives

This systematic review aims to describe the impact penicillin TDM has on health outcomes, including antimicrobial resistance (AMR).

Methods

Studies measuring penicillins in patient samples that adjusted regimens according to the result, and reported health outcomes were selected. Study bias was assessed according to study type. Included study characteristics were tabulated and described by narrative synthesis.

Results

Three randomized controlled trials (RCTs), 16 cohort studies, and 9 case studies were included. No RCTs showed statistically significant improvements in health outcomes. Five cohort studies showed improvement in at least one health outcome associated with target attainment. However, there was a high risk of bias in all studies for health outcomes. One study assessed the impact of penicillin TDM on AMR and found that improved target attainment was associated with suppression of resistance. No studies found a detrimental effect of penicillin TDM.

Conclusions

There is little evidence to suggest that TDM improves health outcomes, however neither health outcomes nor impact on AMR were adequately addressed. Variations in TDM implementation meant that a meta-analysis was not suitable. Penicillin TDM needs standardization, however there is currently no clear evidence of optimal conditions. Suitably powered studies are required to resolve the ambiguity surrounding the impact of TDM on clinical outcomes, including AMR. Further, standardized protocols and concentration targets need to be identified for TDM to be implemented successfully.

Population pharmacokinetics and dosing simulations of amoxicillin in obese adults receiving co-amoxiclav

BACKGROUND

Pneumonia, skin and soft tissue infections are more frequent in obese patients and are most often treated by co-amoxiclav, using similar dosing regimens to those used for non-obese subjects. No data are available on amoxicillin pharmacokinetics among obese subjects receiving co-amoxiclav.

MATERIALS AND METHODS

Prospective, single-centre, open-label, non-randomized, crossover pharmacokinetic trial having enrolled obese otherwise healthy adult subjects. A first dose of co-amoxiclav (amoxicillin/clavulanate 1000/200 mg) was infused IV over 30 min, followed by a second dose (1000/125 mg) administered orally, separated by a washout period of ≥24 h. We assayed concentrations of amoxicillin by a validated ultra HPLC-tandem MS technique. We estimated population pharmacokinetic parameters of amoxicillin by non-linear mixed-effect modelling using the SAEM algorithm developed by Monolix.

RESULTS

Twenty-seven subjects were included in the IV study, with 24 included in the oral part of the study. Median body weight and BMI were 109.3 kg and 40.6 kg/m2, respectively. Amoxicillin pharmacokinetics were best described by a two-compartment model with first-order elimination. Mean values for clearance, central volume, intercompartmental clearance and peripheral volume were, respectively, 14.6 L/h, 9.0 L, 4.2 L/h and 6.4 L for amoxicillin. Oral bioavailability of amoxicillin was 79.7%. Amoxicillin Cmax after oral administration significantly reduced with weight (P = 0.013). Dosing simulations for amoxicillin predicted that most of the population will achieve the pharmacodynamic target of fT>MIC ≥40% with the regimen of co-amoxiclav 1000/200 mg (IV) or 1000/125 mg (oral) q8h for MICs titrated up to 0.5 mg/L (IV) and 1 mg/L (oral).

CONCLUSIONS

Pharmacokinetic/pharmacodynamic goals for amoxicillin can be obtained in obese subjects.

A narrative review of predictors for β-lactam antibiotic exposure during empirical treatment in critically ill patients

INTRODUCTION

: Emerging studies suggest that antibiotic pharmacokinetics (PK) are difficult to predict in critically ill patients. The high intra- and inter-patient PK variability makes it challenging to accurately predict the appropriate dosage required for a given patient. Identifying patients at risk could help clinicians to consider more individualized dosing regimens and perform therapeutic drug monitoring. We provide an overview of relevant predictors associated with target (non-)attainment of β-lactam antibiotics in critically ill patients.

AREAS COVERED

: This narrative review summarizes patient and clinical characteristics that can help to predict the attainment of target serum concentrations and to provide guidance on antimicrobial dose optimization. Literature was searched using Embase and Medline database, focusing on β-lactam antibiotics in critically ill patients.

EXPERT OPINION

: Adequate concentration attainment can be anticipated in critically ill patients prior to initiating empiric β-lactam antibiotic therapy based on readily available demographic and clinical factors. Male gender, younger age, and augmented renal clearance were the most significant predictors for target non-attainment and should be considered in further investigations to develop dosing algorithms for optimal β-lactam therapy.

Obesity as a Risk Factor Among Hospitalized Patients with Infective Endocarditis

Objective

Obesity contributes to diagnostic and management challenges for many hospitalized patients. The impact of obesity on in-hospital outcomes in patients with infective endocarditis has not been studied and was the focus of this investigation.

Method

We used the 2013 and 2014 Nationwide Inpatient Sample to identify adults ≥18 years of age with a principle diagnosis of endocarditis. We divided the sample into 2 groups based on presence of absence of obesity. Multivariate linear and logistic regression analysis was used to compare in-hospital mortality, valvular replacement, length of stay (LOS), and hospitalization charges.

Results

A total of 24 494 adults 18 years and older were hospitalized with infective endocarditis, of which 2625 were classified as obese. Patients with obesity were older (mean age, 57.8 ± 0.3 vs 54.3 ± 0.6 years; P < .01), more likely to be female (50.1% vs 36.1%; P < .01), and had more comorbidities (Charlson comorbidity score ≥ 3, 50.6% vs 28.8%; P < .01). Multivariate regression analysis found no differences between the 2 groups for mortality or repairs or replacements for any valve. On evaluation of resource utilization, patients with obesity had longer average LOS (13.9 days; confidence interval [CI], 12.7–15.1 vs 12.4 days; CI, 12.0–12.8; P = .016) and higher total hospital charges (US $160 789.90; CI, $140.922.40–$180 657.50 vs US $130 627.20; CI, $123 916.70–$137 337.70; P <.01). After adjustment for LOS for total hospital charges, there was no observed difference $11436.26 (CI, -$6649.07–$29521.6; P = .22).

Conclusions

. Obesity does not significantly impact in-hospital mortality or surgical valvular interventions among patients hospitalized with infective endocarditis, but obesity is associated with increased utilization of hospital resources.

Electrochemical Aptamer-Based Sensors for Improved Therapeutic Drug Monitoring and High-Precision, Feedback-Controlled Drug Delivery

The electrochemical aptamer-based (E-AB) sensing platform appears to be a convenient (rapid, single-step, and calibration-free) and modular approach to measure concentrations of specific molecules (irrespective of their chemical reactivity) directly in blood and even in situ in the living body. Given these attributes, the platform may thus provide significant opportunities to render therapeutic drug monitoring (the clinical practice in which dosing is adjusted in response to plasma drug measurements) as frequent and convenient as the measurement of blood sugar has become for diabetics. The ability to measure arbitrary molecules in the body in real time could even enable closed-loop feedback control over plasma drug levels in a manner analogous to the recently commercialized controlled blood sugar systems. As initial exploration of this, we describe here the selection of an aptamer against vancomycin, a narrow therapeutic window antibiotic for which therapeutic monitoring is a critical part of the standard of care, and its adaptation into an electrochemical aptamer-based (E-AB) sensor. Using this sensor, we then demonstrate: (i) rapid (seconds) and convenient (single-step and calibration-free) measurement of plasma vancomycin in finger-prick-scale samples of whole blood, (ii) high-precision measurement of subject-specific vancomycin pharmacokinetics (in a rat animal model), and (iii) high-precision, closed-loop feedback control over plasma levels of the drug (in a rat animal model). The ability to not only track (with continuous-glucose-monitor-like measurement frequency and convenience) but also actively control plasma drug levels provides an unprecedented route toward improving therapeutic drug monitoring and, more generally, the personalized, high-precision delivery of pharmacological interventions.

Clinical practice in prevention of fracture-related infection: An international survey among 1197 orthopaedic trauma surgeons

INTRODUCTION

Open fractures are still a challenge in orthopaedic trauma surgery, and compared to closed fractures, the rate of complications including fracture-related infection (FRI) remains significantly higher. Although different guidelines on prevention of FRI have been published in past decades, the current recommendations vary significantly. The objectives of this international questionnaire were to evaluate clinical practice procedures for the prevention of FRI in open fractures and to evaluate adherence to available guidelines.

METHODS

A 17-item questionnaire regarding prophylaxis against infection in fracture care was administered by SurveyMonkey® and was sent via blast e-mail to all users of AOTrauma (Davos, Switzerland).

RESULTS

Overall, 1197 orthopaedic trauma surgeons answered the survey. Although cephalosporins were the most commonly prescribed agents for perioperative antibiotic prophylaxis (PAP) in open fractures, a total of 13 different antibiotics were mentioned in the survey. Furthermore, the duration of PAP was extremely variable with a tendency towards longer treatment periods with increasing open fracture severity. The majority of surgeons (71%) agreed that the optimal duration of PAP was not well defined in the literature. The use of local anti-infective agents varied significantly, although all options received additional votes with increasing injury severity. Some of the other surgical aspects addressed in this review were associated with debridement and irrigation. A delay of six hours from injury to the first debridement was acceptable to 47% of surgeons, but delays were tolerable. Normal saline was the solution used most often for wound irrigation in open fractures (89%), with low-pressure irrigation being applied most commonly (55%).

CONCLUSIONS

This international survey provided an overview of clinical practice in FRI prevention, particularly in open fracture cases. The treatment of these serious injuries remains heterogeneous. A major issue is the lack of consensus concerning type and duration of PAP. Furthermore, there seems to be no agreement on the indication for the use of local anti-infective agents. Overall, it is unknown what the repercussions are of this lack of internationally accepted guidelines on daily clinical practice, but it is clear that standardised treatment protocols are preferable in the current medical landscape.

Optimization of the treatment with beta-lactam antibiotics in critically ill patients-guidelines from the French Society of Pharmacology and Therapeutics (Société Française de Pharmacologie et Thérapeutique-SFPT) and the French Society of Anaesthesia and Intensive Care Medicine (Société Française d'Anesthésie et Réanimation-SFAR)

BACKGROUND

Beta-lactam antibiotics (βLA) are the most commonly used antibiotics in the intensive care unit (ICU). ICU patients present many pathophysiological features that cause pharmacokinetic (PK) and pharmacodynamic (PD) specificities, leading to the risk of underdosage. The French Society of Pharmacology and Therapeutics (SFPT) and the French Society of Anaesthesia and Intensive Care Medicine (SFAR) have joined forces to provide guidelines on the optimization of beta-lactam treatment in ICU patients.

METHODS

A consensus committee of 18 experts from the two societies had the mission of producing these guidelines. The entire process was conducted independently of any industry funding. A list of questions formulated according to the PICO model (Population, Intervention, Comparison, and Outcomes) was drawn-up by the experts. Then, two bibliographic experts analysed the literature published since January 2000 using predefined keywords according to PRISMA recommendations. The quality of the data identified from the literature was assessed using the GRADE® methodology. Due to the lack of powerful studies having used mortality as main judgement criteria, it was decided, before drafting the recommendations, to formulate only "optional" recommendations.

RESULTS

After two rounds of rating and one amendment, a strong agreement was reached by the SFPT-SFAR guideline panel for 21 optional recommendations and a recapitulative algorithm for care covering four areas: (i) pharmacokinetic variability, (ii) PK-PD relationship, (iii) administration modalities, and (iv) therapeutic drug monitoring (TDM). The most important recommendations regarding βLA administration in ICU patients concerned (i) the consideration of the many sources of PK variability in this population; (ii) the definition of free plasma concentration between four and eight times the Minimal Inhibitory Concentration (MIC) of the causative bacteria for 100% of the dosing interval as PK-PD target to maximize bacteriological and clinical responses; (iii) the use of continuous or prolonged administration of βLA in the most severe patients, in case of high MIC bacteria and in case of lower respiratory tract infection to improve clinical cure; and (iv) the use of TDM to improve PK-PD target achievement.

CONCLUSIONS

The experts strongly suggest the use of personalized dosing, continuous or prolonged infusion and therapeutic drug monitoring when administering βLA in critically ill patients.

Optimisation of antimicrobial dosing based on pharmacokinetic and pharmacodynamic principles

While suboptimal dosing of antimicrobials has been attributed to poorer clinical outcomes, clinical cure and mortality advantages have been demonstrated when target pharmacokinetic (PK) and pharmacodynamic (PD) indices for various classes of antimicrobials were achieved to maximise antibiotic activity. Dosing optimisation requires a good knowledge of PK/PD principles. This review serves to provide a foundation in PK/PD principles for the commonly prescribed antibiotics (β-lactams, vancomycin, fluoroquinolones and aminoglycosides), as well as dosing considerations in special populations (critically ill and obese patients). PK principles determine whether an appropriate dose of antimicrobial reaches the intended pathogen(s). It involves the fundamental processes of absorption, distribution, metabolism and elimination, and is affected by the antimicrobial's physicochemical properties. Antimicrobial pharmacodynamics define the relationship between the drug concentration and its observed effect on the pathogen. The major indicator of the effect of the antibiotics is the minimum inhibitory concentration. The quantitative relationship between a PK and microbiological parameter is known as a PK/PD index, which describes the relationship between dose administered and the rate and extent of bacterial killing. Improvements in clinical outcomes have been observed when antimicrobial agents are dosed optimally to achieve their respective PK/PD targets. With the rising rates of antimicrobial resistance and a limited drug development pipeline, PK/PD concepts can foster more rational and individualised dosing regimens, improving outcomes while simultaneously limiting the toxicity of antimicrobials.

The Surgical Infection Society Revised Guidelines on the Management of Intra-Abdominal Infection

BACKGROUND

Previous evidence-based guidelines on the management of intra-abdominal infection (IAI) were published by the Surgical Infection Society (SIS) in 1992, 2002, and 2010. At the time the most recent guideline was released, the plan was to update the guideline every five years to ensure the timeliness and appropriateness of the recommendations.

METHODS

Based on the previous guidelines, the task force outlined a number of topics related to the treatment of patients with IAI and then developed key questions on these various topics. All questions were approached using general and specific literature searches, focusing on articles and other information published since 2008. These publications and additional materials published before 2008 were reviewed by the task force as a whole or by individual subgroups as to relevance to individual questions. Recommendations were developed by a process of iterative consensus, with all task force members voting to accept or reject each recommendation. Grading was based on the GRADE (Grades of Recommendation Assessment, Development, and Evaluation) system; the quality of the evidence was graded as high, moderate, or weak, and the strength of the recommendation was graded as strong or weak. Review of the document was performed by members of the SIS who were not on the task force. After responses were made to all critiques, the document was approved as an official guideline of the SIS by the Executive Council.

RESULTS

This guideline summarizes the current recommendations developed by the task force on the treatment of patients who have IAI. Evidence-based recommendations have been made regarding risk assessment in individual patients; source control; the timing, selection, and duration of antimicrobial therapy; and suggested approaches to patients who fail initial therapy. Additional recommendations related to the treatment of pediatric patients with IAI have been included.

SUMMARY

The current recommendations of the SIS regarding the treatment of patients with IAI are provided in this guideline.

Application of guidelines for aminoglycosides use in French hospitals in 2013-2014

In 2011, the French Agency for Safety of Health Products issued guidelines underlining the principles of proper aminoglycosides' use. The aim of the survey was to evaluate adherence to these guidelines two years after their issue. Characteristics of patients receiving aminoglycosides were recorded by voluntary facilities during a 3-month survey in 2013-2014. The modalities of aminoglycosides treatment were analysed by comparison with the French guidelines. A total of 3,323 patients were included by 176 facilities. Patients were mainly hospitalized in medical wards (33.0%), and treated for urinary-tract infections (24.7%). Compliance regarding the clinical indication and the daily aminoglycosides dose was observed in 65.2% and 62.9% of the cases, respectively. A 30-min once-daily IV administration was recorded in 62.5% of the cases. Aminoglycosides treatment duration was appropriate (≤5 days) for 93.6% of the patients. When considering the four criteria together, 23.2% of the patients had a treatment regimen aligned with the guidelines. Requests for measurements of peak and trough AG serum concentrations matched the guidelines in 24.9% and 67.4% of the cases, respectively. Two years after guidelines issue, aminoglycosides use remains unsatisfactory in French health-care facilities. Efforts should be made for guidelines promotion, especially regarding the issue of underdosing.

Antimicrobial therapy in obesity: a multicentre cross-sectional study

Objectives

Evidence indicates a relationship between obesity and infection. We assessed the prevalence of obesity in hospitalized patients and evaluated its impact on antimicrobial management.

Methods

Three National Health Service hospitals in London in 2011–12 were included in a cross-sectional study. Data from all adult admissions units and medical and surgical wards were collected. Patient data were collected from the medication charts and nursing and medical notes. Antimicrobial therapy was defined as ‘complicated’ if the patient's therapy met two or more of the following criteria: (i) second- or third-line therapy according to local policy; (ii) intravenous therapy where an alternative oral therapy was appropriate; (iii) longer than the recommended duration of therapy as per local policy recommendations; (iv) repeated courses of therapy to treat the same infection; and (v) specialist advice on antimicrobial therapy provided by the medical microbiology or infectious diseases teams.

Results

Of the 1014 patients included in this study, 22% (225) were obese, 69% (696) were normal/overweight and 9% (93) were underweight. Obese patients were significantly more likely to have more complicated antimicrobial therapy than normal/overweight and underweight patients (36% versus 19% and 23%, respectively, P = 0.002). After adjustment for hospital, age group, comorbidities and the type of infection, obese patients remained at significantly increased odds of receiving complicated antimicrobial therapy compared with normal/overweight patients (OR = 2.01, 95% CI 1.75–3.45).

Conclusions

One in five hospitalized patients is obese. Compared with the underweight and normal/overweight, the antimicrobial management in the obese is significantly more complicated.