Therapeutic drug monitoring of antimicrobials

Vancomycin therapeutic drug monitoring in paediatrics

AIM

Vancomycin guidelines for therapeutic drug monitoring (TDM) aim to maximise efficacy while minimising toxicity and resistance. Vancomycin is effective against Staphylococcus aureus when it achieves area under the concentration-time curve (AUC)/minimum inhibitory concentration (MIC) > 400. Studies in children have shown that target trough concentrations poorly correlate to AUC/MIC > 400; however, they are used in practice for clinical convenience. This review in paediatric inpatients aims to audit performance against TDM guidelines and consider what changes are needed to optimise vancomycin monitoring.

METHODS

Vancomycin prescriptions in patients younger than 18 years old were collected over a 15-month period. Primary outcome measures were vancomycin initial dose (mg/kg/day) and the timing and result of first trough concentration (mg/L). Secondary outcome measures were the numbers achieving recommended targets and whether appropriate dose adjustments were made in response to TDM.

RESULTS

A total of 133 courses reached the time when TDM should occur. Average patient age was 6.5 years, and the average initial dose was 52.55 mg/kg/day (range 19.05-86.54 mg/kg). Only 25% of courses (n = 34) had a trough concentration measured at the recommended time. The mean trough concentration was 11.6 mg/L (range < 2.0-39.7). Of 40 patients with a low trough concentration, 50% continued without dose adjustment.

CONCLUSION

As shown in the literature, there is a poor correlation between the vancomycin dose given and the trough concentration achieved. Given that recommendations for trough concentration monitoring are designed to simplify the process yet are poorly adhered to, a strategic plan to address these issues is needed.

Caspofungin PK in critically ill patients after the first and fourth doses: suggestions for therapeutic drug monitoring?

We describe caspofungin pharmacokinetics (PK) after the first and fourth doses in 20 critically ill septic patients. Monte Carlo simulation was used to analyze the probability of target attainment (PTA) (AUC/MIC > 865) for Candida spp. Caspofungin concentrations were analyzed by HPLC in plasma and urine. A great variability in PK parameters was observed after both doses. Patients were divided in two groups according to their AUC values (AUC ≤ 75 mg h/L cut-off). In the low-AUC group Cmax, Cmin and AUC were lower, while Vd and Cl were higher than in the high-AUC group (p < 0.05, both at day 1 and 4). The mean 24-h urinary recovery of the drug was 8 ± 6.3% (day1) and 9.8 ± 6.3 (day4). Monte Carlo simulation analysis (0.03-1 mg/L MIC-range) showed that PTA was guaranteed only for MICs ≤ 0.03 mg/L in the low-AUC group, and for MICs ≤ 0.06 mg/L in the high-AUC group. No group had a PTA ≥ 90% for 0.125 mg/L MIC (the epidemiological cut-off). Mortality was higher in low-AUC group (p < 0.01). In our 'real-world' population, no clinical data can predict which patient will have lower, suboptimal caspofungin exposure, therefore we suggest TDM to optimize caspofungin therapy and reduce the risk of selecting resistances (CEAVC, 32366/2015; OSS.15.114, NCT03798600).

Oral Ciprofloxacin Pharmacokinetics in Healthy Mexican Volunteers and Other Populations: Is There Interethnic Variability?

BACKGROUND

There is evidence that the pharmacokinetics of certain drugs in Mexicans may differ with respect to other ethnic groups. On the other hand, there is controversy about the existence of interethnic variability in the pharmacokinetics of ciprofloxacin.

AIM OF THE STUDY

To study oral ciprofloxacin pharmacokinetics in Mexicans at various dose levels and make comparisons with other populations in order to gain insight on interethnic variability.

METHODS

Healthy Mexican volunteers received oral ciprofloxacin as 250 mg and 500 mg immediate-release tablets or a 1,000 mg extended-release formulation. Plasma concentration against time curves were constructed, and pharmacokinetic parameters were compared with those reported for other populations.

RESULTS

Ciprofloxacin pharmacokinetics in Mexicans was linear and no significant differences between males and females were detected. When several populations were compared, it appeared that bioavailability in Mexicans was similar to that of Caucasians, being lower than that of Asians. These variations were attenuated when data were normalized by body weight.

CONCLUSIONS

Ciprofloxacin pharmacokinetics exhibit interethnic variability, Asians exhibiting an increased bioavailability with regard to Mexicans and Caucasians. Data suggest that these differences are due to body weight.

Development and validation of a UPLC-MS/MS method for simultaneous quantification of levofloxacin, ciprofloxacin, moxifloxacin and rifampicin in human plasma: Application to the therapeutic drug monitoring in osteoarticular infections

BACKGROUND

Fluoroquinolones and rifampicin are antibiotics frequently used for the treatment of osteoarticular infections, and their therapeutic drug monitoring is recommended. The aim of this study was to develop and validate a rapid and selective method of simultaneous quantification of levofloxacin, ciprofloxacin, moxifloxacin and rifampicin with short pretreatment and run times in order to be easily used in clinical practice.

METHODS

After a simple protein precipitation of plasma samples, the chromatographic separation was performed using an ultra-performance liquid chromatography system coupled with mass tandem spectrometry in a positive ionization mode. The mobile phase consisted of a gradient elution of water-formic acid (100:0.1, v/v)-ammonium acetate 2 mM (A) and methanol-formic acid (100:0.1, v/v)-ammonium acetate 2 mM (B) at a flow rate at 0.3 mL/min.

RESULTS

Analysis time was 5 min per run, and all analytes and internal standards eluted within 0.85-1.69 minutes. The calibration curves were linear over the range from 0.5-30 μg/mL for levofloxacin, ciprofloxacin, moxifloxacin and rifampicin with linear regression coefficients above 0.995 for all analytes. The intra-day and inter-day coefficients of variation were below 10 % for lower and higher concentration. This method was successfully applied to drug monitoring in patients with an osteoarticular infection.

CONCLUSION

A simple, rapid, and selective liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous quantification of levofloxacin, ciprofloxacin, moxifloxacin and rifampicin in human plasma.

Embryotoxic and teratogenic profile of tretracycline at environmentally relevant concentrations on Cyprinus carpio

The objective of this work was to evaluate whether tetracycline (TC) in environmentally relevant concentrations was able to induce alterations to embryonic development and teratogenic effects in oocytes and embryos of Cyprinus carpio. For this purpose, an embryolethality study was conducted and the lethal concentration 50 (LC₅₀) and effective concentration 50 of malformations (EC₅₀) were calculated, and with these data the teratogenic index (TI) was determined. The main alterations to embryonic development and the teratogenic effects produced by TC on embryos of C. carpio were determined using the Kimmel and Hersem scale adapted for Cyprinus carpio. LC₅₀ and EC₅₀ were respectively 500.08 and 145.3 μg L^-1.TC was shown to be teratogenic with teratogenic index of 3.44, and the main malformations identified in concentrations of 90-900 μg L^-1 were malformation in tail, modified chorda structure, pericardical edema, scoliosis and malformations of the heart. A significant decrease in concentration-dependent in Kimmel and Hersem score was observed. The results allow us to conclude that TC at environmentally relevant concentrations is capable of inducing embryotoxic and teratogenic effects, generating risk in the integrity of the common carp C. Carpio.

Standards of aminoglycoside therapeutic drug monitoring in a South African private hospital: perspectives and implications

Background

Therapeutic drug monitoring (TDM) is essential to ensure that aminoglycoside peak concentrations are high enough for effective antimicrobial treatment and trough levels are low enough to minimise toxicity. Inappropriate utilisation of TDM may lead to suboptimal therapy, toxicity and waste of resources. This study aimed to investigate the standard of aminoglycoside TDM performed in adult hospitalised patients.

Design

An observational, descriptive, cross-sectional study.

Setting

A 221-bed private hospital.

Participants

All patients, older than 18 years, on intravenous aminoglycosides for more than 48 hours were included.

Interventions

None, was observational. A computerised database and patient files were used to obtain the information required for this study. Descriptive statistical analysis was used.

Main outcomes measures

Aminoglycoside blood levels and estimated glomerular filtration rate (eGFR) in the patients.

Results

One hundred and three (103) patients were included: 65 on gentamicin and 38 on amikacin. Blood levels were performed in only 19 gentamicin (29.23%) and 22 amikacin (57.89%) patients. Trough levels were taken more than 2 hours before the next dose in 12 gentamicin (63.16%) and 12 amikacin (54.54%) patients. The majority of patients (96.92% on gentamicin and 84.21% on amikacin) received once daily doses. TDM was performed in all patients with an estimated glomerular filtration rate (eGFR) lower than 60 mL/min/1.73m² and in 23.31% of gentamicin patients and 56.76% of amikacin patients with an eGFR higher than 60 mg/min/1.73m².

Conclusions

Incorrect sampling times and unnecessary levels taken in patients with normal renal function indicate a need for aminoglycoside treatment guidelines in the private hospital.

Funding

None

Highly Sensitive Detection of the Antibiotic Ciprofloxacin by Means of Fiber Enhanced Raman Spectroscopy

Sepsis and septic shock exhibit a rapid course and a high fatality rate. Antibiotic treatment is time-critical and precise knowledge of the antibiotic concentration during the patients’ treatment would allow individual dose adaption. Over- and underdosing will increase the antimicrobial efficacy and reduce toxicity. We demonstrated that fiber enhanced Raman spectroscopy (FERS) can be used to detect very low concentrations of ciprofloxacin in clinically relevant doses, down to 1.5 µM. Fiber enhancement was achieved in bandgap shifted photonic crystal fibers. The high linearity between the Raman signals and the drug concentrations allows a robust calibration for drug quantification. The needed sample volume was very low (0.58 µL) and an acquisition time of 30 s allowed the rapid monitoring of ciprofloxacin levels in a less invasive way than conventional techniques. These results demonstrate that FERS has a high potential for clinical in-situ monitoring of ciprofloxacin levels.

Population pharmacokinetics of amikacin in patients with pediatric cystic fibrosis

INTRODUCTION

Amikacin is commonly used in patients with pediatric cystic fibrosis (CF) for the treatment of pulmonary exacerbations. Amikacin efficacy is related to maximum plasma concentration/minimum inhibitory concentration (Cmax/MIC) ratio >8. Pharmacokinetic data in patients with pediatric CF are scarce. The aim of this study was to develop a population pharmacokinetic (PopPK) model describing amikacin disposition in patients with pediatric CF.

METHODS

CF patients under 18 years of age with pulmonary exacerbation who received amikacin were enrolled. Patients received different amikacin regimens (30 mg^-1  kg^-1  day^-1 every 8, 12, or 24 hours) depending on the patient's status and hospital protocols. Amikacin serum levels were obtained for therapeutic drug monitoring. PopPK model was developed using MONOLIX Suite-2018R1 (Lixoft).

RESULTS

A total of 39 patients (114 amikacin concentrations) were included in this study. Population estimates for the elimination rate constant (k) and the volume of distribution (V) were 0.541 hours^-1 and 0.451 L/kg, respectively. Between-subject and between-occasion variability were 53% and 16.5% for k and 31% and 22% for V, respectively. Bodyweight was a significant covariate associated with V. Based on simulations, almost 70% of the patients receiving 30 mg^-1  kg^-1  day^-1 every 24 hours would achieve a Cmax/MIC ratio >8 which is an appropriate therapeutic goal while no patient in the other two groups (Q8 and Q12) would achieve that objective.

CONCLUSIONS

The regimen of 30  mg^-1  kg^-1  day^-1 every 24 hours more adequately fulfilled the therapeutic target for amikacin. Although all our patients had good clinical results and a good adverse-events profile, further studies are necessary to redefine the optimal treatment strategy.

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.

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.

Review of the pharmacokinetic properties of nitrofurantoin and nitroxoline

Nitrofurantoin and nitroxoline are oral antibiotics for the treatment or prophylaxis of acute urinary tract infections. New interest in both these drugs is increasing because of the emergence of resistance to other antibiotics, but knowledge of their pharmacokinetics (PK) is lacking since they were developed before the advent of standardized research for drug approval. The aims of this review were to (i) summarize the PK data reported in the literature and (ii) to identify PK knowledge gaps. The current body of PK knowledge of both drugs appears to be poor and mainly based on old studies. Nitrofurantoin PK values were obtained from studies using many variables, e.g. formulations, crystal sizes and analytical methods, resulting in high interindividual variability in PK parameters and no uniform PK profile. Clinical experience and PK data for nitroxoline are even more limited since the drug is registered in only Germany and a few (Eastern European) countries. Clinical studies in relevant patient populations are needed with commercially available nitrofurantoin and nitroxoline formulations at approved dosing regimens to more fully characterize their PK profiles, and to investigate the influence of patient characteristics on these profiles in order to optimize efficacy and avoid toxicity and emergence of resistance. Only with this updated knowledge and efficacy data from well-structured trials can both drugs maintain their antimicrobial activity against uropathogens.

Prevention of drug-related complications in cystic fibrosis

PURPOSE OF REVIEW

Due to continuous development of new drugs and better treatment strategies, survival of patients with cystic fibrosis has changed dramatically. Recently, targeted therapy of cystic fibrosis transmembrane conductance regulator (CFTR) modulators have become available. Despite these promising developments, treatment of this complex multiorgan disease constitutes a high and variable amount of other drugs. Complications of pharmacotherapeutic treatment are, therefore, expected to become more prevalent. This gives cause to review drug-related side effects in this new era in cystic fibrosis treatment.

RECENT FINDINGS

We will discuss cystic fibrosis-related pharmacotherapies with a focus on indication of treatment, side effects and their complications, drug--drug interactions, and options to monitor and prevent drug-induced toxicity. Many recent publications about pharmacotherapy in cystic fibrosis, focus on antifungal therapy and CFTR modulators. We will give an overview of the most important studies.

SUMMARY

With increased life expectancy which is, in part, because of better treatment options, the burden of pharmacotherapy in cystic fibrosis patients will increase. This has a high impact on quality of life as pharmacotherapy is time consuming and may cause side effects. Therefore, it is very important to be aware of possible pharmacotherapy-related side effects and their complications, drug--drug interactions, and options to monitor and prevent drug-induced toxicity.

Urinary antibacterial activity of fosfomycin and nitrofurantoin at registered dosages in healthy volunteers

Given emerging uropathogen resistance to more recent antibiotics, old antibiotics used for uncomplicated urinary tract infection (UTI) warrant re-examination. In this study, the urinary antibacterial activities of fosfomycin and nitrofurantoin were investigated by determining the urinary inhibitory titre and urinary bactericidal titre against uropathogens in urine samples from female volunteers following administration of single-dose fosfomycin (3 g) or nitrofurantoin (50 mg q6h or 100 mg q8h). Urine samples were collected over 48 h (fosfomycin) or 6 or 8 h (nitrofurantoin), with drug levels quantified with every void. Fosfomycin concentrations ranged from <0.75 mg/L [lower limit of quantification (LLOQ)] to 5729.9 mg/L and nitrofurantoin concentrations ranged from <4 mg/L (LLOQ) to 176.3 mg/L (50 mg q6h) or 209.4 mg/L (100 mg q8h). There was discrepancy in the response to fosfomycin between Escherichia coli and Klebsiella pneumoniae, with fosfomycin displaying strong bactericidal activity for 48 h against E. coli but moderate bactericidal activity for 18 h against K. pneumoniae. This effect was not related to the strain's baseline minimum inhibitory concentration but rather to the presence of a resistant subpopulation. Maximum titres of nitrofurantoin were obtained during the first 2 h, but no antibacterial effect was found in most samples regardless of the dose. In the rare samples in which antibacterial activity was detectable, titres were comparable for both species tested. These findings confirm doubts regarding fosfomycin administration in UTIs caused by K. pneumoniae and reveal a discrepancy between nitrofurantoin's measurable ex vivo activity and its clinical effect over multiple dosing intervals.

Application of Aluminum Hydroxide for Improvement of Label-Free SERS Detection of Some Cephalosporin Antibiotics in Urine

This report is dedicated to development of surface-enhanced Raman spectroscopy (SERS) based analysis protocol for detection of antibiotics in urine. The key step of the protocol is the pretreatment of urine before the detection to minimize background signal. The pretreatment includes extraction of intrinsic urine components using aluminum hydroxide gel (AHG) and further pH adjusting of the purified sample. The protocol was tested by detection of a single antibiotic in artificially spiked samples of real urine. Five antibiotics of cephalosporin class (cefazolin, cefoperazone, cefotaxime, ceftriaxone, and cefuroxime) were used for testing. SERS measurements were performed using a portable Raman spectrometer with 638 nm excitation wavelength and silver nanoparticles as SERS substrate. The calibration curves of four antibiotics (cefuroxime is the exception) cover the concentrations required for detection in patient’s urine during therapy (25/100‒500 μg/mL). Random error of the analysis (RSD < 20%) and limits of quantification (20‒90 μg/mL) for these antibiotics demonstrate the applicability of the protocol for reliable quantitative detection during therapeutic drug monitoring. The detection of cefuroxime using the protocol is not sensitive enough, allowing only for qualitative detection. Additionally, time stability and batch-to-batch reproducibility of AHG were studied and negative influence of the pretreatment protocol and its limitations were estimated and discussed.

Microdialysis combined with liquid chromatography-tandem mass spectrometry for the quantitation of gemifloxacin and its application to a muscle penetration study in healthy and MRSA-infected rats

Pharmacological efficacy is based on the drug concentration in target tissues, which usually cannot be represented by the plasma concentration. The purpose of this study was to compare the pharmacokinetic characteristics of gemifloxacin in plasma and skeletal muscle and evaluate its tissue penetration in both healthy and MRSA (methicillin-resistant Staphylococcus aureus)-infected rats. A microdialysis (MD) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to determine free gemifloxacin concentrations in rat plasma and skeletal muscle simultaneously. The in vivo recoveries of MD were 23.21% ± 3.42% for skeletal muscle and 20.62% ± 3.19% for plasma, and were concentration independent. We provided evidence that the method developed here meets FDA requirements. Additionally, this method was successfully applied to the determination of free gemifloxacin in rats. Muscle and blood dialysates were collected after an 18 mg/kg intravenous bolus dose. The mean areas under the concentration-time curves (AUCs) from 0 to 9 h for skeletal muscle and plasma were 3641.50 ± 915.65 h*ng/mL and 7068.32 ± 1964.19 h*ng/mL in MRSA-infected rats and 3774.72 ± 700.36 h*ng/mL and 6927.49 ± 1714.86 h*ng/mL in healthy rats, respectively. There was no significant difference (P>0.05) in gemifloxacin exposure between healthy rats and MRSA-infected rats for plasma or muscle. The low ratio of AUC0-9 muscle to AUC0-9 plasma suggested lower drug exposure in skeletal muscle than in plasma for both healthy and MRSA-infected rats. Our study suggested that the administration of gemifloxacin according to drug levels in plasma to treat local infection is unreasonable and might result in an inadequate dose regimen.

India's National Action Plan for antimicrobial resistance - An overview of the context, status, and way ahead

Antimicrobial resistance (AMR) is a multifaceted complex problem with momentous consequences for individuals as well as health-care systems. Understanding the gravity of the problem, the World Health Assembly has adopted the Global Action Plan on AMR in the year 2015 as a part of the tripartite collaboration with World Health Organization, Food and Agricultural Organization, and World Organization for Animal Health. India's National Action Plan (NAP) for AMR was released in April 2017 by the Union Ministry of Health and Family Welfare. The objectives of the NAP include improving awareness, enhancing surveillance measures, strengthening infection prevention and control, research and development, promoting investments, and collaborative activities to control AMR. On the basis of the NAP, various states have begun the process of initiating their State Action Plans. The aim of this article is to highlight some of the main components of the NAP and to make family physicians, general practitioners, and other stakeholders aware of the issue of AMR and its factors and what can be done. The article also discusses some of the challenges in implementation of NAP such as varied perceptions about antibiotic use and AMR among key stakeholders, inappropriate antibiotic use owing to a number of reasons, lack of diagnostic facilities, widespread use of antibiotics in various sectors, environmental contamination because of pharmaceutical industry, agricultural and hospital waste, gaps in infection prevention and control, and difficulty in enforcing regulations. Similar to other low-middle income countries (LMICs), lack of sufficient finances remains a major challenge in NAP implementation in India as well. Overall, a strong political will, inter-sectoral co-ordination between public and private sectors and comprehensive strengthening of the healthcare systems are necessary to achieve the desired forward momentum.

Clinically relevant pharmacokinetic knowledge on antibiotic dosing among intensive care professionals is insufficient: a cross-sectional study

BACKGROUND

Antibiotic exposure in intensive care patients with sepsis is frequently inadequate and is associated with poorer outcomes. Antibiotic dosing is challenging in the intensive care, as critically ill patients have altered and fluctuating antibiotic pharmacokinetics that make current one-size-fits-all regimens unsatisfactory. Real-time bedside dosing software is not available yet, and therapeutic drug monitoring is typically used for few antibiotic classes and only allows for delayed dosing adaptation. Thus, adequate and timely antibiotic dosing continues to rely largely on the level of pharmacokinetic expertise in the ICU. Therefore, we set out to assess the level of knowledge on antibiotic pharmacokinetics among these intensive care professionals.

METHODS

In May 2018, we carried out a cross-sectional study by sending out an online survey on antibiotic dosing to more than 20,000 intensive care professionals. Questions were designed to cover relevant topics in pharmacokinetics related to intensive care antibiotic dosing. The preliminary pass mark was set by members of the examination committee for the European Diploma of Intensive Care using a modified Angoff approach. The final pass mark was corrected for clinical relevance as assessed for each question by international experts on pharmacokinetics.

RESULTS

A total of 1448 respondents completed the survey. Most of the respondents were intensivists (927 respondents, 64%) from 97 countries. Nearly all questions were considered clinically relevant by pharmacokinetic experts. The pass mark corrected for clinical relevance was 52.8 out of 93.7 points. Pass rates were 42.5% for intensivists, 36.1% for fellows, 24.8% for residents, and 5.8% for nurses. Scores without correction for clinical relevance were worse, indicating that respondents perform better on more relevant topics. Correct answers and concise clinical background are provided.

CONCLUSIONS

Clinically relevant pharmacokinetic knowledge on antibiotic dosing among intensive care professionals is insufficient. This should be addressed given the importance of adequate antibiotic exposure in critically ill patients with sepsis. Solutions include improved education, intensified pharmacy support, therapeutic drug monitoring, or the use of real-time bedside dosing software. Questions may provide useful for teaching purposes.

Urinary piperacillin/tazobactam pharmacokinetics in vitro to determine the pharmacodynamic breakpoint for resistant Enterobacteriaceae

Urinary tract infections caused by multidrug-resistant Enterobacteriaceae are a growing burden worldwide. Recent studies of urinary pharmacokinetics described high piperacillin/tazobactam (TZP) concentrations in urine, but it is unknown whether this results in treatment efficacy. This study investigated the pharmacodynamics of TZP in a static in vitro model for Enterobacteriaceae to determine the concentration-effect relationship and ultimately the required free (unbound) time above the minimum inhibitory concentration (fT_>MIC) required for bacterial killing. The static simulation model investigated TZP fT_>MIC between 0% and 100%. Resistant Escherichia coli and Klebsiella pneumoniae isolates with piperacillin/tazobactam MICs of 4096/512, 1024/128 and 128/16 mg/L were investigated; two of the three organisms were carbapenemase-producers. Clinical efficacy was determined as a 3-log reduction over the dosing interval by comparing interval growth with controls. TZP was observed to exhibit time dependence for all organisms. The fT_>MIC was determined to be 37.5%, 37.5% and 50% for MICs of 4096/512, 1024/128 and 128/16 mg/L, respectively. Linear regression identified the overall target to be 49.85 ± 16.9% fT_>MIC. In conclusion, bactericidal activity against TZP-resistant Enterobacteriaceae occurred at 49.85 ± 16.9% fT_>MIC. This suggests that highly resistant urinary organisms, including carbapenemase-producers, with MICs up to 4096/512 mg/L could be treated with TZP. Further investigations are required to elucidate urinary breakpoints and to explore the impact of different resistance mechanisms.

Clay-biochar composites for sorptive removal of tetracycline antibiotic in aqueous media

The focus of this research was to synthesize novel clay-biochar composites by incorporating montmorillonite (MMT) and red earth (RE) clay materials in a municipal solid waste (MSW) biochar for the adsorptive removal of tetracycline (TC) from aqueous media. X-ray Fluorescence Analysis (XRF), Fourier Transform Infrared Spectroscopy (FTIR), Powder X-ray Diffraction (PXRD) and Scanning Electron Microscopy (SEM) were used for the characterization of the synthesized raw biochar (MSW-BC) and clay-biochar composites (MSW-MMT and MSW-RE). Results showed that minute clay particles were dispersed on biochar surfaces. The FTIR bands due to Si-O functional group vibrations in the spectra of the clay-biochar composites provided further evidence for successful composite formation. The kinetic TC adsorption data of MSW-MMT were well fitted to the Elovich model expressing high surface activity of biochar and involvement of multiple mechanisms in the adsorption. The kinetic TC adsorption data of MSW-BC and MSW-RE were fitted to the pseudo second order model indicating dominant contribution of chemisorption mechanism during the adsorption. The adsorption differentiation obtained in the kinetic studies was mainly due to the structure of the combined clay material. The adsorption isotherm data of all the adsorbents were well fitted to the Freundlich model suggesting that the adsorption of TC onto the materials occurred via both physisorption and chemisorption mechanisms. In comparison to the raw biochar and MSW-RE, MSW-MMT exhibited higher TC adsorption capacity. Therefore, MSW-MMT clay-biochar composite could be applied in the remediation of TC antibiotic residues in contaminated aqueous media.

Antibiotic use in critical illness

OBJECTIVE

To provide a review on the current use of antimicrobials with a discussion on the pharmacokinetic and pharmacodynamic profiles of antimicrobials in critically ill patients, the challenges of drug resistance, the use of diagnostic testing to direct therapy, and the selection of the most likely efficacious antimicrobial protocol.

ETIOLOGY

Patients in the intensive care unit often possess profound pathophysiologic changes that can complicate antimicrobial therapy. Although many antimicrobials have known pharmacodynamic profiles, critical illness can cause wide variations in their pharmacokinetics. The two principal factors affecting pharmacokinetics are volume of distribution and drug clearance. Understanding the interplay between critical illness, drug pharmacokinetics, and antimicrobial characteristics (ie, time-dependent vs concentration-dependent) may improve antimicrobial efficacy and patient outcome.

DIAGNOSIS

Utilizing bacterial culture and susceptibility can aid in identifying drug resistant infections, selecting the most appropriate antimicrobials, and hindering the future development of drug resistance.

THERAPY

Having a basic knowledge of antimicrobial function and how to use diagnostics to direct therapeutic treatment is paramount in managing this patient population. Diagnostic testing is not always available at the time of initiation of antimicrobial therapy, so empiric selections are often necessary. These empiric choices should be made based on the location of the infection and the most likely infecting bacteria.

PROGNOSIS

Studies have demonstrated the importance of moving away from a "one dose fits all" approach to antimicrobial therapy. Instead there has been a move toward an individualized approach that takes into consideration the pharmacokinetic and pharmacodynamic variabilities that can occur in critically ill patients.

A critical review of HPLC-based analytical methods for quantification of Linezolid

Linezolid is a synthetic antimicrobial agent belonging to the oxazolidinone class. Since its approval in the year 2000 until now, linezolid remains the main representative drug for the oxazolidinone class of drugs, which is used in therapy due to its unique mode of action, which involves inhibition of protein synthesis. As linezolid holds great importance in antimicrobial therapy, it is necessary to compile the various analytical methods that have been reported in the literature for its analysis. Analytical techniques used for pharmaceutical analyses and therapeutic drug monitoring play an important role in comprehending the aspects regarding bioavailability, bioequivalence, and therapeutic monitoring during patient follow-ups. Even though linezolid has had the approval for clinical use for more than 18 years now, most of the analytical methods for its determination reported in the scientific literature are the ones which utilize HPLC. Therefore, the present review provides a summary of the HPLC-based methods used in the determination and quantification of linezolid in different matrices since the time of its discovery.

Optimizing dosing of nitrofurantoin from a PK/PD point of view: What do we need to know?

Nitrofurantoin is an old antibiotic and an important first-line oral antibiotic for the treatment of uncomplicated urinary tract infections. However despite its long term use for over 60 years, little information is available with respect to its dose justification and this may be the reason of highly variable recommended doses and dosing schedules. Furthermore, nitrofurantoin is not a uniform product -crystal sizes of nitrofurantoin, and therefore pharmacokinetic properties, differ significantly by product. Moreover, pharmacokinetic profiling of some products is even lacking, or difficult to interpret because of its unstable chemical properties. Pharmacokinetic and pharmacodynamic data is now slowly becoming available. This review provides an overview of nitrofurantoins antibacterial, pharmacokinetic and pharmacodynamic properties. This shows that a clear rationale of current dosing regimens is scanty.

Usefulness of therapeutic drug monitoring of piperacillin and meropenem in routine clinical practice: a prospective cohort study in critically ill patients

Background

Beta-lactam anti-infective levels after standard dosing have been shown to be subtherapeutic when renal clearance is augmented.

Objective

To determine if piperacillin and meropenem are found to be in their therapeutic range in infected critically ill patients when administered by continuous intravenous infusion (CII) assisted by a therapeutic drug monitoring (TDM) report issued by the pharmacy service.

Methods

This prospective non-controlled intervention study evaluated septic patients in an intensive care unit. Patients received a loading dose of meropenem or piperacillin-tazobactam and the antibiotics were afterwards administered by CII. Blood concentrations were determined by high-performance liquid chromatography assays. The adequacy of β-lactam therapy in the cohort subjected to intervention was assessed by determining whether plasma levels during CII were >4 times the informed minimum inhibitory concentration during the first 96 hours of treatment.

Results

A total of 124 patients were subject to TDM during antibiotic treatment but, for the analysis of the fulfilment of pharmacodynamic requirements, data from 31/124 (25%) were excluded. Of the whole cohort of treatment courses, 57/93 (61.3%) reached the target level. Plasma levels were adequate in 41/70 (58.6%) and 16/23 (69.6%) of the patients treated with piperacillin-tazobactam and meropenem, respectively. Globally, recommendations based on TDM results were followed in 35/93 (37.6%) of the treatment courses.

Conclusions

The results of the study show that, in critically ill patients with sepsis, there is a significant proportion of treatment courses where target levels are not reached even if the antibiotics are administered by CII and TDM support is provided by the pharmacy service. This TDM support should be offered on a real-time basis to be really useful.

Simultaneous Quantification of Nine Antimicrobials by LC-MS/MS for Therapeutic Drug Monitoring in Critically Ill Patients

BACKGROUND

Adequate antibiotic treatment is a prerequisite for the successful treatment of systemic infections. Based on accumulating scientific evidence, a fixed dosage regimen can lead to insufficient and ineffective antibiotic therapy. Thus, the aim of this study was to develop and validate a simplified, but sensitive method for the simultaneous quantification of antimicrobials by using liquid chromatography with tandem mass spectrometry (LC-MS/MS) for the development of personalized therapy regimens using therapeutic drug monitoring.

METHODS

A method was developed for the simultaneous quantification of 9 antimicrobials (aciclovir, ampicillin, cefuroxime, ciprofloxacin, meropenem, metronidazole, piperacillin, rifampicin, and tazobactam) in lithium-heparin plasma. A simple sample preparation method and a chromatographic run time of 10 minutes enabled the quick processing of the samples. The method was validated according to the guidelines for bioanalytical method validation of the European Medicines Agency and addressed sensitivity, specificity, linearity, accuracy, precision, dilution integrity, carry-over, recovery, matrix effects, and stability.

RESULTS

The chromatographic run time was 10 minutes and antimicrobials eluted at retention times ranging from 1.1 to 2.2 minutes. Calibration curve for all antimicrobials was linear over a range of 1-100 mg/L, and a 2-fold or 5-fold dilution of the samples was possible. The method accuracy ranged from 85.1% to 114.9% for all measured antimicrobials, and the within- and between-run precision values were <11.9% and <16.5% for the lower limit of quantification. No interferences and carry-over were observed. The samples were stable for at least 5 hours at room temperature or in the autosampler (10°C).

CONCLUSIONS

The LC-MS/MS method developed in this study is appropriate and practical for the therapeutic drug monitoring of antimicrobials in the daily clinical laboratory practice because of its short analysis time, the need for a small amount of plasma, high specificity, and accuracy.

Whole Genome Sequencing and Comparative Genomics Analyses of Pandoraea sp. XY-2, a New Species Capable of Biodegrade Tetracycline

Few bacteria are resistant to tetracycline and can even biodegrade tetracycline in the environment. In this study, we isolated a bacterium Pandoraea sp. XY-2, which could biodegrade 74% tetracycline at pH 7.0 and 30°C within 6 days. Thereafter, we determined the whole genome sequence of Pandoraea sp. XY-2 genome is a single circular chromosome of 5.06 Mb in size. Genomic annotation showed that two AA6 family members-encoding genes and nine glutathione S-transferase (GSTs)-encoding genes could be relevant to tetracycline biodegradation. In addition, the average nucleotide identities (ANI) analysis between the genomes of Pandoraea sp. XY-2 and other Pandoraea spp. revealed that Pandoraea sp. XY-2 belongs to a new species. Moreover, comparative genome analysis of 36 Pandoraea strains identified the pan and specific genes, numerous single nucleotide polymorphisms (SNPs), insertions, and deletion variations (InDels) and different syntenial relationships in the genome of Pandoraea sp. XY-2. Finally, the evolution and the origin analysis of genes related to tetracycline resistance revealed that the six tetA(48) genes and two specificgenes tetG and tetR in Pandoraea sp. XY-2 were acquired by horizontal gene transfer (HGT) events from sources related to Paraburkholderia, Burkholderia, Caballeronia, Salmonella, Vibrio, Proteobacteria, Pseudomonas, Acinetobacter, Flavimaricola, and some unidentified sources. As a new species, Pandoraea sp. XY-2 will be an excellent resource for the bioremediation of tetracycline-contaminated environment.

Pharmacokinetics-pharmacodynamics issues relevant for the clinical use of beta-lactam antibiotics in critically ill patients

Antimicrobials are among the most important and commonly prescribed drugs in the management of critically ill patients and beta-lactams are the most common antibiotic class used. Critically ill patient's pathophysiological factors lead to altered pharmacokinetics and pharmacodynamics of beta-lactams.A comprehensive bibliographic search in PubMed database of all English language articles published from January 2000 to December 2017 was performed, allowing the selection of articles addressing the pharmacokinetics or pharmacodynamics of beta-lactam antibiotics in critically ill patients.In critically ill patients, several factors may increase volume of distribution and enhance renal clearance, inducing high intra- and inter-patient variability in beta-lactam concentration and promoting the risk of antibiotic underdosing. The duration of infusion of beta-lactams has been shown to influence the fT > minimal inhibitory concentration and an improved beta-lactam pharmacodynamics profile may be obtained by longer exposure with more frequent dosing, extended infusions, or continuous infusions.The use of extracorporeal support techniques in the critically ill may further contribute to this problem and we recommend not reducing standard antibiotic dosage since no drug accumulation was found in the available literature and to maintain continuous or prolonged infusion, especially for the treatment of infections caused by multidrug-resistant bacteria.Prediction of outcome based on concentrations in plasma results in overestimation of antimicrobial activity at the site of infection, namely in cerebrospinal fluid and the lung. Therefore, although no studies have assessed clinical outcome, we recommend using higher than standard dosing, preferably with continuous or prolonged infusions, especially when treating less susceptible bacterial strains at these sites, as the pharmacodynamics profile may improve with no apparent increase in toxicity.A therapeutic drug monitoring-guided approach could be particularly useful in critically ill patients in whom achieving target concentrations is more difficult, such as obese patients, immunocompromised patients, those infected by highly resistant bacterial strains, patients with augmented renal clearance, and those undergoing extracorporeal support techniques.

Evaluation of Renal Function Estimation Formulas Specific to Dynamic Renal Function for Drug Dosing in Critically Ill Patients

OBJECTIVES

The study compared estimated creatinine clearance (eCrCl) between the Cockcroft-Gault (CG) equation and the Jelliffe, Chiou, and Brater equations designed for estimation in dynamic renal function and resulting antimicrobial dosing concordance of five antimicrobials (cefepime, meropenem, piperacillin/tazobactam, vancomycin, and fluconazole) commonly used in the intensive care unit (ICU).

METHODS

Electronic medical records were used to identify the target patient population. Analysis of variance tests with repeated measures were performed to compare eCrCl. Bowker's tests of symmetry were applied to compare the dosing regimen discordance between CG and candidate equations.

RESULTS

From January 1, 2008 through December 31, 2012, we identified 387 patients with acute kidney injury (AKI), among whom 62% (n = 240) were older adults (65 years and older) and 46% (n = 178) were obese (body mass index ≥30). In the declining phase of renal function, eCrCl means were different between the CG and Brater equations (32.0 vs 26.1 mL/min, P < 0.001). The dosing regimen discordance rates (CG vs candidate equations) in declining renal function varied from 19.3% to 25% and were statistically significant for cefepime and meropenem (P < 0.001) based on Food and Drug Administration recommendations for dose adjustment. In the improving phase, eCrCl means were different (P < 0.001) between CG (43.0 mL/min) and candidate formulas (Brater 47.9, Chiou 31.7, and Jelliffe 55.3 mL/min). The dosing regimen discordance rates (CG vs candidate equations) in the improving phase varied from 8.3% to 39% and were statistically significant for all 5 antimicrobials (P < 0.001).

CONCLUSIONS

Differences in eCrCl between CG and candidate formulas were observed in surgical ICU patients with acute kidney injury. Discordant dosing recommendations may affect antimicrobial regimens in ICU patients with dynamic renal function.

Multiplex Therapeutic Drug Monitoring by Isotope-dilution HPLC-MS/MS of Antibiotics in Critical Illnesses

There is an ever-increasing demand for the therapeutic drug monitoring of antibiotics in many clinical facilities, particularly with regard to the implementation of hospital antibiotic stewardship programs. In the current work, we present a multiplex high-performance liquid chromatography-tandem mass spectrometry (HPCL-MS/MS) protocol for the quantification of cefepime, meropenem, ciprofloxacin, moxifloxacin, linezolid, and piperacillin, commonly used antibiotics in intensive care units. The method was previously comprehensively validated according to the guideline of the European Medicines Agency. After a rapid sample cleanup, the analytes are separated on a C8 reverse-phase HPLC column within 4 minutes and quantified with the corresponding stable isotope-labeled internal standards in electrospray ionization (ESI+) mass spectrometry in multiple reaction time monitoring (MRM). The presented method uses a simple instrumentation setting with uniform chromatographic conditions, allowing for the daily and robust antibiotic therapeutic drug monitoring in clinical laboratories. The calibration curve spans the pharmacokinetic concentration range, thereby including antibiotic amounts close to the minimal inhibitory concentration (MIC) of susceptible bacteria and peak concentrations (Cmax) that are obtained with bolus administration regimens. Without the necessity of the serum dilution before the sample cleanup, the area under the curve for an administered antibiotic can be obtained through multiple measurements.

An evaluation of risk factors to predict target concentration non-attainment in critically ill patients prior to empiric β-lactam therapy

To determine whether target concentration non-attainment can be anticipated in critically ill patients prior to initiating empiric β-lactam antibiotic therapy based on readily available clinical factors. Retrospective review of consecutive patients treated with piperacillin or meropenem and who underwent therapeutic drug monitoring (TDM) at St Vincent's Hospital (Sydney, Australia) between January 2013 and December 2015 was performed. Predefined subgroups were patients who received continuous renal replacement therapy (CRRT) and those who did not (non-CRRT). Potential risk factors were evaluated by correlation with β-lactam antibiotic trough concentrations (C_min) lower than or equal to targeted minimum inhibitory concentration (MIC). Only the first drug concentration after initiation of the antibiotic treatment was included to reflect empirical dose selection. A total of n = 249 patients (piperacillin, n = 169; meropenem, n = 80) were investigated. For non-CRRT patients (n = 210), multivariate analysis demonstrated the following: male gender (p = 0.006); younger age (p = 0.015); prescribed daily antibiotic dose less than 1.5 times the product information recommendations (p = 0.004); lack of positive microbiology (p = 0.006); lower overall illness severity (p = 0.005); and estimated glomerular filtration rate (eGFR) ≥ 90 mL/min/1.73 m² (p < 0.001), to be associated with C_min ≤ MIC. No predictor variable was found to be significantly associated with C_min ≤ MIC for the CRRT cohort. Evaluating the risk of target concentration non-attainment using simple clinical factors is possible at the bedside for non-CRRT patients prior to empiric antibiotic initiation. Clinicians should be wary of selecting doses based on the product information especially when treating younger male patients with apparently 'normal' renal function.

[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).

Clinical applications of population pharmacokinetic models of antibiotics: Challenges and perspectives

Because of increasing antimicrobial resistance and the shortage of new antibiotics, there is a growing need to optimize the use of old and new antibiotics. Modelling of the pharmacokinetic/pharmacodynamic (PK/PD) characteristics of antibiotics can support the optimization of dosing regimens. Antimicrobial efficacy is determined by susceptibility of the drug to the microorganism and exposure to the drug, which relies on the PK and the dose. Population PK models describe relationships between patients characteristics and drug exposure. This article highlights three clinical applications of these models applied to antibiotics: 1) dosing evaluation of old antibiotics, 2) setting clinical breakpoints and 3) dosing individualization using therapeutic drug monitoring (TDM). For each clinical application, challenges regarding interpretation are discussed. An important challenge is to improve the understanding of the interpretation of modelling results for good implementation of the dosing recommendations, clinical breakpoints and TDM advices. Therefore, also background information on PK/PD principles and approaches to analyse PK/PD data are provided.

Too much of a good thing: a retrospective study of β-lactam concentration-toxicity relationships

Objectives

To determine the existence of concentration-toxicity relationships for common β-lactam antibiotic adverse effects and define thresholds above which toxicity is more likely.

Patients and methods

Retrospective review of consecutive patients treated with piperacillin, meropenem or flucloxacillin who underwent therapeutic drug monitoring (TDM) at St Vincent's Hospital (Sydney, Australia) between January 2013 and December 2015. Adverse events investigated included neurotoxicity, nephrotoxicity, hepatotoxicity and opportunistic Clostridium difficile infection. Toxicity was measured using observational grading criteria, clinical assessment and relevant serum biomarkers. These findings were correlated with trough TDM measurements at the time of toxicity presentation.

Results

TDM results from 378 patients (piperacillin = 223, meropenem = 94 and flucloxacillin = 61) were investigated. There was no difference in baseline patient characteristics across antibiotic groups. A statistically significant elevation in mean serum trough concentrations (Cmin) was found in patients diagnosed with neurotoxicity (piperacillin, P < 0.01; meropenem, P = 0.04; flucloxacillin, P = 0.01) and those who developed nephrotoxicity whilst being treated with piperacillin (P < 0.01) or meropenem (P < 0.01). Incidence of hepatotoxicity and C. difficile was not related to Cmin. Threshold concentrations for which there is 50% risk of developing a neurotoxicity event (piperacillin, Cmin >361.4 mg/L; meropenem, Cmin >64.2 mg/L; flucloxacillin, Cmin >125.1 mg/L) or nephrotoxicity (piperacillin, Cmin >452.65 mg/L; meropenem, Cmin >44.45 mg/L) varied across antibiotics.

Conclusions

Our data reveal an association between toxic concentrations for a number of β-lactam agents and neurotoxic/nephrotoxic effects. We have defined threshold concentrations above which these toxicities become more likely. Clinicians should balance concerns for therapeutic efficacy with potential toxicity when considering aggressive therapy.

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.

Simple and robust LC–MS/MS analysis method for therapeutic drug monitoring of micafungin

Aim: To develop a simple and robust LC–MS/MS method to quantify concentrations of micafungin in human plasma for pharmacokinetic studies and therapeutic drug monitoring. Methods: Sample preparation involved protein precipitation with acetonitrile:methanol (83:17% v/v) and [13C6]-micafungin as internal standard. A rapid and selective method for micafungin was validated across a range of 0.200–10.0 mg/l. Results: The calculated accuracy for the eight-point calibration ranged from 0.7 to 5.3%. Within-run precision ranged from 0.8 to 5.9%, between-run precision ranged from 0.7 to 3.1%, and overall precision ranged from 1.3 to 6.6%. Conclusion: A simple and robust LC–MS/MS method for analyzing micafungin in human plasma has been validated and was utilized for quantification of micafungin.

Exploring the Use of C-Reactive Protein to Estimate the Pharmacodynamics of Vancomycin

BACKGROUND

C-reactive protein (CRP) pharmacodynamic (PD) models have the potential to provide adjunctive methods for predicting the individual exposure response to antimicrobial therapy. We investigated CRP PD linked to a vancomycin pharmacokinetic (PK) model using routinely collected data from noncritical care adults in secondary care.

METHODS

Patients receiving intermittent intravenous vancomycin therapy in secondary care were identified. A 2-compartment vancomycin PK model was linked to a previously described PD model describing CRP response. PK and PD parameters were estimated using a Non-Parametric Adaptive Grid technique. Exposure-response relationships were explored with vancomycin area-under-the-concentration-time-curve (AUC) and EC50 (concentration of drug that causes a half maximal effect) using the index, AUC:EC50, fitted to CRP data using a sigmoidal Emax model.

RESULTS

Twenty-nine individuals were included. Median age was 62 (21-97) years. Fifteen (52%) patients were microbiology confirmed. PK and PD models were adequately fitted (r 0.83 and 0.82, respectively). There was a wide variation observed in individual Bayesian posterior EC50 estimates (6.95-48.55 mg/L), with mean (SD) AUC:EC50 of 31.46 (29.22). AUC:EC50 was fitted to terminal CRP with AUC:EC50 >19 associated with lower CRP value at 96-120 hours of therapy (100 mg/L versus 44 mg/L; P < 0.01).

CONCLUSIONS

The use of AUC:EC50 has the potential to provide in vivo organism and host response data as an adjunct for in vitro minimum inhibitory concentration data, which is currently used as the gold standard PD index for vancomycin therapy. This index can be estimated using routinely collected clinical data. Future work must investigate the role of AUC:EC50 in a prospective cohort and explore linkage with direct patient outcomes.

Determinants of amikacin first peak concentration in critically ill patients

Amikacin antimicrobial effect has been correlated with the ratio of the peak concentration (C_max ) to the minimum inhibitory concentration. A target C_max ≥ 60-80 mg/L has been suggested. It has been shown that such target is not achieved in a large proportion of critically ill patients in intensive care units. A retrospective analysis was performed to examine the determinants of C_max ≥ 80 mg/L on the first peak in 339 critically ill patients treated by amikacin. The influence of available variables on C_max target attainment was analyzed using a classification and regression tree (CART) and logistic regression. Mean C_max in the 339 patients was 73.0 ± 23.9 mg/L, with a target attainment rate (TAR, C_max ≥ 80 mg/L) of 37.5%. In CART analysis, the strongest predictor of amikacin target peak attainment was dose per kilogram of lean body weight (dose/LBW). TAR was 60.1% in patients with dose/LBW ≥ 37.8 vs. 19.9% in patients with lower dose/LBW (OR = 6.0 (95% CI: 3.6-10.2)). Renal function was a secondary predictor of C_max . Logistic regression analysis identified dose per kilogram of ideal body weight (OR = 1.13 (95% CI: 1.09-1.17)) and creatinine clearance (OR = 0.993 (95% CI: 0.988-0.998)) as predictors of target peak achievement. Based on our results, an amikacin dose ≥ 37.8 mg/kg of LBW should be used to optimize the attainment of C_max ≥ 80 mg/L after the first dose in critically ill patients. An even higher dose may be necessary in patients with normal renal function.

Therapeutic Drug Monitoring of Gentamicin Peak Concentrations in Critically Ill Patients

BACKGROUND

Adequate gentamicin peak concentrations (Cmax) are important for optimal clinical efficacy. Within a critically ill patient, substantial variability in Cmax can occur over time, hampering the usefulness of therapeutic drug monitoring (TDM). The aim of this study was to evaluate the effect of gentamicin dosing based on Cmax after the first dose on gentamicin target attainment in critically ill patients.

METHODS

From gentamicin-treated critically ill patients, dosing information, clinical parameters, and serum concentrations were collected prospectively. A population pharmacokinetic model was developed using nonlinear mixed-effects modeling to estimate Cmax after each dose. To evaluate the usefulness of routine TDM, percentages of Cmax within (%Cther, 15-20 mg/L), above (>20 mg/L), and below (%Csubther, <15 mg/L) the therapeutic range after the first and second doses were compared. In addition, simulations were performed to evaluate the impact of TDM.

RESULTS

Four hundred sixteen measurements from 59 patients receiving 130 gentamicin doses were included. In the 30 patients who received >1 dose, TDM increased %Cther from 40% after a first median dose of 5.0 mg/kg to 50% after the second dose, and decreased %Csubther from 47% to 30%. Simulations using a 5 mg/kg starting dose revealed %Cther after the second dose of 28.4% without and 36.8% with TDM and %Csubther of 56.9% and 29.3%, respectively. Increasing the simulated starting dose to 6 mg/kg increased %Cther after the first dose from 27.7% to 33.5% and decreased %Csubther from 58.6% to 35.6%. TDM after a first dose of 6 mg/kg had no substantial effect on %Cther or %Csubther after the second dose.

CONCLUSIONS

Gentamicin dosing based on Cmax after the first dose increased %Cther and decreased %Csubther, but did not result in therapeutic Cmax in half of the patients. When simulating a higher starting dose, %Csubther after the first dose decreased, and TDM showed no additional influence. These data suggest that a starting dose of 6 mg/kg should be considered and that repeated Cmax measurements are not of added value.

Delivering precision antimicrobial therapy through closed-loop control systems

Sub-optimal exposure to antimicrobial therapy is associated with poor patient outcomes and the development of antimicrobial resistance. Mechanisms for optimizing the concentration of a drug within the individual patient are under development. However, several barriers remain in realizing true individualization of therapy. These include problems with plasma drug sampling, availability of appropriate assays, and current mechanisms for dose adjustment. Biosensor technology offers a means of providing real-time monitoring of antimicrobials in a minimally invasive fashion. We report the potential for using microneedle biosensor technology as part of closed-loop control systems for the optimization of antimicrobial therapy in individual patients.

Validated HPLC-UV detection method for the simultaneous determination of ceftolozane and tazobactam in human plasma

Aim: A simple, rapid, economical and sensitive HPLC-UV method was developed for the simultaneous quantification of ceftolozane and tazobactam in plasma samples. Methodology: After deproteinization followed by a liquid–liquid back-extraction, the compounds were separated on a C18 column (150 mm × 4.6 mm, 5 μm) with UV-visible detection at 220 nm. The mobile phase consisted of acetonitrile and potassium dihydrogenphosphate buffer at pH 3.0 (8:92, v/v), delivered isocratically at a flow rate of 1.0 ml/min and at a column oven temperature of 30°C. Cefepime was used as an internal standard. Results: Linearity was achieved in the concentration range of 0.50–100.00 μg/ml for ceftolozane and 0.25–50.00 μg/ml for tazobactam. The intra- and interday precision showed good reproducibility with coefficients of variation of less than 9.26% for ceftolozane and 9.62% for tazobactam. Conclusion: The sample preparation procedure avoids expensive or time-consuming steps used by other previously published methods. The methodology was validated according to standard guidelines and was used for quantification of ceftolozane and tazobactam in plasma samples from critically ill patients.

An evaluation of serum gentamicin concentrations and bacterial susceptibility to gentamicin in equine practice

Background

Therapeutic drug monitoring and minimum inhibitory concentration (MIC) data allow more informed use of gentamicin.

Hypothesis/Objectives

To measure peak and trough serum gentamicin concentrations in horses after a 6.6 mg/kg dose of gentamicin given IV and the MIC of gentamicin of bacteria for which gentamicin might be selected.

Methods

Retrospective analysis of hospital records. Peak and trough plasma gentamicin concentrations were measured after 6.6 mg/kg gentamicin IV in 339 hospitalized horses. The MIC of gentamicin was measured for 503 isolates from ambulatory practice and 33 from hospital practice. The distribution of gentamicin concentrations and MIC results were compared to current recommendations for MIC breakpoints.

Results

The median serum gentamicin concentration at 60 minutes after administration (C_60min) was 21.4 μg/mL with a distribution indicating that bacteria with MIC ≥2 μg/mL were unlikely to be exposed to sufficient gentamicin for effective killing. Approximately 90% of isolates from ambulatory practice and 36% of hospital isolates had MICs at or below breakpoints for susceptibility with most of the remainder unlikely to be responsive, even to higher IV doses.

Conclusions and Clinical Importance

Gentamicin at a dosage of 6.6 mg/kg IV is likely to be effective against the majority of infections encountered in ambulatory practice, but less effective in an equine hospital. Because there was a dichotomy of most bacteria as being clearly susceptible or clearly resistant to gentamicin, it appears unlikely that higher doses would have been more efficacious, especially in the hospitalized population in our study.

Individualised medicine: why we need Bayesian dosing

Individualised drug dosing has been shown to improve patient outcomes and reduce adverse drug events. One method of individualised medicine is the Bayesian approach, which uses prior information about how the population responds to therapy, to inform clinicians about how a specific individual is responding to their current therapy. This information is then used to make changes to the dose. Studies using a Bayesian approach to adjust drug dosing have shown that clinicians are able to achieve a therapeutic range quicker than standard practice. If concentration is related to a pharmacodynamic end-point, this means that the drug will be more effective, and the side-effects will be minimised. Unfortunately, the software options to assist with Bayesian dosing in Australia are limited. The aims of this article are to demystify the concepts of Bayesian dosing, set the context of the Bayesian approach using reference to other dosing strategies and discuss its benefits over current dosing methods for a number of drugs. The article is targeted to medical and pharmacy clinicians, and there is a practical clinical case to demonstrate how this method could be used in everyday clinical practice.

Simultaneous quantification of cefepime, meropenem, ciprofloxacin, moxifloxacin, linezolid and piperacillin in human serum using an isotope-dilution HPLC-MS/MS method

The aim of the current study was to develop and validate a robust multi-analyte high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method for simultaneous quantification of cefepime, meropenem, ciprofloxacin, moxifloxacin, linezolid and piperacillin, which are the most commonly used antibiotics in intensive care units. Sample clean-up included a protein precipitation protocol, followed by chromatographic separation on a C₈ reverse phase HPLC column within 4 min, using a formic acid-ammonium formiate methanol step-elution gradient. All compounds were detected with electrospray ionization (ESI+) mass spectrometry in multiple reaction time monitoring. The method was validated according to the protocol from the European Medicines Agency and was thoroughly evaluated for interferences and quantification linearity. Linear relationships between peak area responses and drug concentrations were obtained in the range of 0.25-200 mg/l for cefepime, 0.25-120 mg/l for meropenem, 0.05-10 mg/l for ciprofloxacin, 0.125-10 mg/l for moxifloxacin, 0.125-50 mg/l for linezolid and 0.5-400 mg/l for piperacillin with an R² > 0.997. Imprecision and inaccuracy values (both intra- and inter-assay) were ≤ 6.8% and ≤10.9% for all analytes in quality control samples, respectively. The assay proved to be selective for the study antibiotics, and the internal standards consistently compensated for matrix effects. The described simple and reliable HPLC-MS/MS assay is a powerful tool for routine TDM of cefepime, meropenem, ciprofloxacin, moxifloxacin, linezolid and piperacillin in human serum in clinical laboratories. With a total process time of approximately 30 min, it allows for accurate and selective quantification up to the expected pharmacokinetic peak concentrations.

Key Components for Antibiotic Dose Optimization of Sepsis in Neonates and Infants

Sepsis in neonates and infants remains a major cause of death despite a decline in child mortality and morbidity over the last decades. A key factor in further reducing poor clinical outcomes is the optimal use of antibiotics in sepsis management. Developmental changes such as maturation of organ function and capacity of drug metabolizing enzymes can affect the pharmacokinetic profile and therefore the antibiotic exposure and response in neonates and infants. Optimal antibiotic treatment of sepsis in neonates and young infants is dependent on several key components such as the determination of treatment phase, the administered dose and the resulted drug exposure and microbiological response. During the initial phase of suspected sepsis, the primary focus of empirical treatment is to assure efficacy. Once bacterial infection as the cause of sepsis is confirmed the focus shifts toward a targeted treatment, ensuring an optimal balance between efficacy and safety. Interpretation of antibiotic exposure and microbiological response in neonates and infants is multifaceted. The response or treatment effect can be determined by the microbiological parameters (MIC) together with the characteristics of the pathogen (time- or concentration dependent). The antibiotic response is influenced by the properties of the causative pathogen and the unique characteristics of the vulnerable patient population such as reduced humoral response or reduced skin barrier function. Therapeutic drug monitoring (TDM) of antibiotics may be used to increase effectiveness while maximizing safety and minimizing the toxicity, but requires expertise in different fields and requires collaborations between physicians, lab technicians, and quantitative clinical pharmacologists. Understanding these clinical, pharmacological, and microbiological components and their underlying relationship can provide a scientific basic for proper antibiotic use and reduction of antibiotic resistance in neonates and infants. This highlights the necessity of a close multidisciplinary collaboration between physicians, pharmacists, clinical pharmacologists and microbiologist to assure the optimal utilization of antibiotics in neonates and young infants.