Population Pharmacokinetics and Pharmacodynamics of Levofloxacin in Acutely Hospitalized Older Patients with Various Degrees of Renal Function

Levofloxacin loaded chitosan and poly-lactic-co-glycolic acid nano-particles against resistant bacteria: Synthesis, characterization and antibacterial activity

BACKGROUND

With the global increase in antibacterial resistance, the challenge faced by developing countries is to utilize the available antibiotics, alone or in combination, against resistant bacterial strains. We aimed to encapsulate the levofloxacin (LVX) into polymeric nanoparticles using biodegradable polymers i.e. Chitosan and PLGA, estimating their physicochemical characteristics followed by functional assessment as nanocarriers of levofloxacin against the different resistant strains of bacteria isolated from biological samples collected from tertiary care hospital in Lahore, Pakistan.

METHODS

LVX-NPs were synthesized using ion gelation and double emulsion solvent-evaporation method employing chitosan (CS) and poly-lactic-co-glycolic acid (PLGA), characterized via FTIR, XRD, SEM, and invitro drug release studies, while antibacterial activity was assessed using Kirby-Bauer disc-diffusion method.

RESULTS

Data revealed that the levofloxacin-loaded chitosan nanoparticles showed entrapment efficiency of 57.14% ± 0.03 (CS-I), 77.30% ± 0.08(CS-II) and 87.47% ± 0.08 (CS-III). The drug content, particle size, and polydispersity index of CS-I were 52.22% ± 0.2, 559 nm ± 31 nm, and 0.030, respectively, whereas it was 66.86% ± 0.17, 595 nm ± 52.3 nm and 0.057, respectively for CS-II and 82.65% ± 0.36, 758 nm ± 24 nm and 0.1, respectively for CS-III. The PLGA-levofloxacin nanoparticles showed an entrapment efficiency of 42.80% ± 0.4 (PLGA I) and 23.80% ± 0.4 (PLGA II). The drug content, particle size and polydispersity index of PLGA-I were 86% ± 0.21, 92 nm ± 10 nm, and 0.058, respectively, whereas it was 52.41% ± 0.45, 313 nm ± 32 nm and 0.076, respectively for PLGA-II. The XRD patterns of both polymeric nanoparticles showed an amorphous nature. SEM analysis reflects the circular-shaped agglomerated nanoparticles with PLGA polymer and dense spherical nanoparticles with chitosan polymer. The in-vitro release profile of PLGA-I nanoparticles showed a sustained release of 82% in 120 h and it was 58.40% for CS-III. Both types of polymeric nanoparticles were found to be stable for up to 6 months without losing any major drug content. Among the selected formulations, CS-III and PLGA-I, CS-III had better antibacterial potency against gram+ve and gram-ve bacteria, except for K. pneumonia, yet, PLGA-I demonstrated efficacy against K. pneumonia as per CSLI guidelines. All formulations did not exhibit any signs of hemotoxicity, nonetheless, the CS-NPs tend to bind on the surface of RBCs.

CONCLUSION

These data suggested that available antibiotics can effectively be utilized as nano-antibiotics against resistant bacterial strains, causing severe infections, for improved antibiotic sensitivity without compromising patient safety.

Population pharmacokinetics of antibacterial agents in the older population: a literature review

INTRODUCTION

Older individuals face an elevated risk of developing bacterial infections. The optimal use of antibacterial agents in this population is challenging because of age-related physiological alterations, changes in pharmacokinetics (PK) and pharmacodynamics (PD), and the presence of multiple underlying diseases. Therefore, population pharmacokinetics (PPK) studies are of great importance for optimizing individual treatments and prompt identification of potential risk factors.

AREA COVERED

Our search involved keywords such as 'elderly,' 'old people,' and 'geriatric,' combined with 'population pharmacokinetics' and 'antibacterial agents.' This comprehensive search yielded 11 categories encompassing 28 antibacterial drugs, including vancomycin, ceftriaxone, meropenem, and linezolid. Out of 127 studies identified, 26 (20.5%) were associated with vancomycin, 14 (11%) with meropenem, and 14 (11%) with piperacillin. Other antibacterial agents were administered less frequently.

EXPERT OPINION

PPK studies are invaluable for elucidating the characteristics and relevant factors affecting the PK of antibacterial agents in the older population. Further research is warranted to develop and validate PPK models for antibacterial agents in this vulnerable population.

Pharmacokinetics of Antibacterial Agents in the Elderly: The Body of Evidence

Infections are important factors contributing to the morbidity and mortality among elderly patients. High rates of consumption of antimicrobial agents by the elderly may result in increased risk of toxic reactions, deteriorating functions of various organs and systems and leading to the prolongation of hospital stay, admission to the intensive care unit, disability, and lethal outcome. Both safety and efficacy of antibiotics are determined by the values of their plasma concentrations, widely affected by physiologic and pathologic age-related changes specific for the elderly population. Drug absorption, distribution, metabolism, and excretion are altered in different extents depending on functional and morphological changes in the cardiovascular system, gastrointestinal tract, liver, and kidneys. Water and fat content, skeletal muscle mass, nutritional status, use of concomitant drugs are other determinants of pharmacokinetics changes observed in the elderly. The choice of a proper dosing regimen is essential to provide effective and safe antibiotic therapy in terms of attainment of certain pharmacodynamic targets. The objective of this review is to perform a structure of evidence on the age-related changes contributing to the alteration of pharmacokinetic parameters in the elderly.

Infant Exposure to Antituberculosis Drugs via Breast Milk and Assessment of Potential Adverse Effects in Breastfed Infants: Critical Review of Data

Infants of mothers treated for tuberculosis might be exposed to drugs via breast milk. The existing information on the exposure of breastfed infants lacks a critical review of the published data. We aimed to evaluate the quality of the existing data on antituberculosis (anti-TB) drug concentrations in the plasma and milk as a methodologically sound basis for the potential risk of breastfeeding under therapy. We performed a systematic search in PubMed for bedaquiline, clofazimine, cycloserine/terizidone, levofloxacin, linezolid, pretomanid/pa824, pyrazinamide, streptomycin, ethambutol, rifampicin and isoniazid, supplemented with update references found in LactMed^®. We calculated the external infant exposure (EID) for each drug and compared it with the recommended WHO dose for infants (relative external infant dose) and assessed their potential to elicit adverse effects in the breastfed infant. Breast milk concentration data were mainly not satisfactory to properly estimate the EID. Most of the studies suffer from limitations in the sample collection, quantity, timing and study design. Infant plasma concentrations are extremely scarce and very little data exist documenting the clinical outcome in exposed infants. Concerns for potential adverse effects in breastfed infants could be ruled out for bedaquiline, cycloserine/terizidone, linezolid and pyrazinamide. Adequate studies should be performed covering the scenario in treated mothers, breast milk and infants.

Safety and Tolerability of Antimicrobial Agents in the Older Patient

Older patients are at high risk of infections, which often present atypically and are associated with high morbidity and mortality. Antimicrobial treatment in older individuals with infectious diseases represents a clinical challenge, causing an increasing burden on worldwide healthcare systems; immunosenescence and the coexistence of multiple comorbidities determine complex polypharmacy regimens with an increase in drug-drug interactions and spread of multidrug-resistance infections. Aging-induced pharmacokinetic and pharmacodynamic changes can additionally increase the risk of inappropriate drug dosing, with underexposure that is associated with antimicrobial resistance and overexposure that may lead to adverse effects and poor adherence because of low tolerability. These issues need to be considered when starting antimicrobial prescriptions. National and international efforts have been made towards the implementation of antimicrobial stewardship (AMS) interventions to help clinicians improve the appropriateness and safety of antimicrobial prescriptions in both acute and long-term care settings. AMS programs were shown to decrease consumption of antimicrobials and to improve safety in hospitalized patients and older nursing home residents. With the abundance of antimicrobial prescriptions and the recent emergence of multidrug resistant pathogens, an in-depth review of antimicrobial prescriptions in geriatric clinical practice is needed. This review will discuss the special considerations for older individuals needing antimicrobials, including risk factors that shape risk profiles in geriatric populations as well as an evidence-based description of antimicrobial-induced adverse events in this patient population. It will highlight agents of concern for this age group and discuss interventions to mitigate the effects of inappropriate antimicrobial prescribing.

SPILF update on bacterial arthritis in adults and children

In 2020 the French Society of Rhumatology (SFR) published an update of the 1990 recommendations for management of bacterial arthritis in adults. While we (French ID Society, SPILF) totally endorse this update, we wished to provide further information about specific antibiotic treatments. The present update focuses on antibiotics with good distribution in bone and joint. It is important to monitor their dosage, which should be maximized according to PK/PD parameters. Dosages proposed in this update are high, with the optimized mode of administration for intravenous betalactams (continuous or intermittent infusion). We give tools for the best dosage adaptation to conditions such as obesity or renal insufficiency. In case of enterobacter infection, with an antibiogram result "susceptible for high dosage", we recommend the requesting of specialized advice from an ID physician. More often than not, it is possible to prescribe antibiotics via the oral route as soon as blood cultures are sterile and clinical have symptoms shown improvement. Duration of antibiotic treatment is 6 weeks for Staphylococcus aureus, and 4 weeks for the other bacteria (except for Neisseria: 7 days).

Factors Contributing to Chronic Kidney Disease following COVID-19 Diagnosis in Pre-Vaccinated Hospitalized Patients

In this study, we aim to evaluate the factors that may contribute to the development of chronic kidney disease following COVID-19 infection among hospitalized patients in two private hospitals in Jakarta, Indonesia. This is a retrospective cohort study between March 2020 and September 2021. Patient selection was conducted with a convenience sampling. All patients (n = 378) meeting the inclusion criteria during the study period were enrolled. Various sociodemographic, laboratory test, and diagnostic parameters were measured before the determination of their correlation with the outcome of COVID-19 infection. In this study, all pre-vaccinated patients with COVID-19 had no history of chronic kidney disease (CKD) prior to hospital admission. From this number, approximately 75.7% of the patients developed CKD following COVID-19 diagnosis. Overall, significant correlations were established between the clinical outcome and the CKD status (p = 0.001). Interestingly, there was a significant correlation between serum creatinine level, glomerular filtration rate (GFR), and CKD (p < 0.0001). Oxygen saturation (p = 0.03), admission to the intensive care unit (ICU) (p < 0.0001), and sepsis (p = 0.005) were factors that were significantly correlated with CKD status. Additionally, the type of antibiotic agent used was significantly correlated with CKD (p = 0.011). While 82.1% of patients with CKD survived, the survival rate worsened if the patients had complications from hyperuricemia (p = 0.010). The patients who received levofloxacin and ceftriaxone had the highest (100%) survival rate after approximately 50 days of treatment. The patients who received the antiviral agent combination isoprinosine + oseltamivir + ivermectin fared better (100%) as compared to those who received isoprinosine + favipiravir (8%). Factors, such as hyperuricemia and the antibiotic agent used, contributed to CKD following COVID-19 hospitalization. Interestingly, the patients who received levofloxacin + ceftriaxone and the patients without sepsis fared the best. Overall, patients who develop CKD following COVID-19 hospitalization have a low survival rate.

Analysis of the Distribution and Drug Resistance of Pathogens in Patients with Urinary Tract Infection in the Eastern Chongming Area of Shanghai from 2018 to 2020

Purpose

The aim of this study was to clarify the distribution and drug resistance of pathogens causing urinary tract infection (UTI) and to provide a scientific reference for the rational application of antibiotics.

Patients and Methods

The results of bacterial identification and drug sensitivity analysis of midstream urine samples in our hospital from January 2018 to December 2020 were retrospectively analyzed. The data were analyzed using WHONET 5.6 and SPSS 26.0 (IBM) software.

Results

In all, 1786 pathogens were isolated from 13,141 midstream urine culture samples. Of these, 1093 (61.2%) were gram-negative bacteria, mainly Escherichia coli [29.1%] and Klebsiella pneumoniae [14.3%]; 543 (30.4%) were gram-positive bacteria, mainly Enterococcus faecium [16.7%] and Enterococcus faecalis [8.4%]; and 150 (8.4%) were fungal isolates, with the most common being Candida albicans (3.7%). The resistance rates of E. coli to piperacillin/tazobactam (3.4% vs 10.0%, p<0.05), ampicillin/sulbactam (43.0% vs 53.8%, p<0.05), and ciprofloxacin (58.0% vs 72.9%, p<0.05) increased significantly. K. pneumoniae was highly sensitive to ertapenem (100%). Two Enterococcus spp were highly sensitive to tigecycline (100%), and a small number of norvancomycin-resistant strains were found. The drug resistance rate of E. faecium to quinupristin was 6.7%. The drug resistance rates of E. faecalis to furantoin and ampicillin were 4.0% and 4.7%, respectively.

Conclusion

The pathogens that cause UTIs in patients are diverse, with the most common being E. coli. The isolated pathogens exhibited different resistance patterns. Antibiotics should be rationally selected based on the resistance patterns of the pathogens.

Antibiotics in urine from general adults in Shenzhen, China: Demographic-related difference in exposure levels

Misuse or overuse of antibiotics can have a variety of detrimental microbial effects. However, the body burden of antibiotics in the general population is currently unclear. In this cross-sectional study, we determined four classes of widely-applied antibiotics (3 imidazoles, 2 sulfonamides, 5 quinolones, and 2 chloramphenicols) in urine samples from 1170 adult residents in Shenzhen, China. Antibiotics were detected in 30.8 % of all urine samples with concentrations ranging from <LOD to 3517 μg/mL, among which metronidazole, ofloxacin and florfenicol were predominant. Notably, antibiotics prohibited for human or veterinary use were detected in 21.0 % of samples, indicating that these antibiotics may still be overused in daily life. We found that the presence of antibiotics in urine is associated with being overweight (OR: 1.386, 95 % CI: 1.056-1.819, p = 0.019) and obesity (OR: 1.862, 95 % CI: 1.103-3.146, p = 0.020) in the adult population. Multilinear regression analysis showed that a percent increase of hydroxy metronidazole was related to 9.86 % positive change of body mass index (p = 0.029). Interestingly, we also found total antibiotic concentration higher in the unmarried group (p = 0.006). Besides, consumption of smoked foods was correlated with urinary antibiotic levels (p = 0.001), indicating smoked meat may be a potential exposure source of veterinary antibiotics. These results highlight the need to reduce human exposure to banned antibiotics. Future research could focus on assessing the health risk and other outcomes of antibiotic overuse.

Population pharmacokinetics and dose optimization of intravenous levofloxacin in hospitalized adult patients

Although levofloxacin has been used for the last 25 years, there are limited pharmacokinetic data to guide levofloxacin dosing in adult patients. This study aimed to develop a population pharmacokinetic model of levofloxacin for adult hospitalized patients and define dosing regimens that attain pharmacokinetic/pharmacodynamic target associated with maximum effectiveness. Blood samples were drawn from 26 patients during one dosing interval. Population pharmacokinetic modelling and dosign simulations were performed using Pmetrics®. Pathogen minimum inhibition concentration (MIC) distribution data from the European Committee on Antimicrobial Susceptibility Testing database was used to analyse fractional target attainment (FTA). A two-compartment model adequately described the data. The final model included estimated glomerular filtration rate (eGFR) to describe clearance. The population estimate for clearance was 1.12 L/h, while the volume of distribution in the central compartment and peripheral compartments were 27.6 L and 28.2 L, respectively. Our simulation demonstrated that an area under free concentration–time curve to MIC ≥ 80 was hardly achieved for pathogens with MIC ≥ 1 mg/L. Low FTA against Pseudomonas aeruginosa and Streptococcus pneumoniae were observed for patients with higher eGFR (≥ 80 mL/min/1.73m²). A daily levofloxacin dose of 1000 mg is suggested to maximise the likelihood of efficacy for adult patients.

Key Factors in Effective Patient-Tailored Dosing of Fluoroquinolones in Urological Infections: Interindividual Pharmacokinetic and Pharmacodynamic Variability

Fluoroquinolones (FQs) are a critical group of antimicrobials prescribed in urological infections as they have a broad antimicrobial spectrum of activity and a favorable tissue penetration at the site of infection. However, their clinical practice is not problem-free of treatment failure, risk of emergence of resistance, and rare but important adverse effects. Due to their critical role in clinical improvement, understanding the dose-response relation is necessary to optimize the effectiveness of FQs therapy, as it is essential to select the right antibiotic at the right dose for the right duration in urological infections. The aim of this study was to review the published literature about inter-individual variability in pharmacological processes that can be responsible for the clinical response after empiric dose for the most commonly prescribed urological FQs: ciprofloxacin, levofloxacin, and moxifloxacin. Interindividual pharmacokinetic (PK) variability, particularly in elimination, may contribute to treatment failure. Clearance related to creatinine clearance should be specifically considered for ciprofloxacin and levofloxacin. Likewise, today, undesired interregional variability in FQs antimicrobial activity against certain microorganisms exists. FQs pharmacology, patient-specific characteristics, and the identity of the local infecting organism are key factors in determining clinical outcomes in FQs use.

Ciprofloxacin in Patients Undergoing Extracorporeal Membrane Oxygenation (ECMO): A Population Pharmacokinetic Study

Extracorporeal membrane oxygenation (ECMO) is utilized to temporarily sustain respiratory and/or cardiac function in critically ill patients. Ciprofloxacin is used to treat nosocomial infections, but data describing the effect of ECMO on its pharmacokinetics is lacking. Therefore, a prospective, observational trial including critically ill adults (n = 17), treated with ciprofloxacin (400 mg 8–12 hourly) during ECMO, was performed. Serial blood samples were collected to determine ciprofloxacin concentrations to assess their pharmacokinetics. The pharmacometric modeling was performed (NONMEM^®) and utilized for simulations to evaluate the probability of target attainment (PTA) to achieve an AUC_0–24/MIC of 125 mg·h/L for ciprofloxacin. A two-compartment model most adequately described the concentration-time data of ciprofloxacin. Significant covariates on ciprofloxacin clearance (CL) were plasma bicarbonate and the estimated glomerular filtration rate (eGFR). For pathogens with an MIC of ≤0.25 mg/L, a PTA of ≥90% was attained. However, for pathogens with an MIC of ≥0.5 mg/L, plasma bicarbonate ≥ 22 mmol/L or eGFR ≥ 10 mL/min PTA decreased below 90%, steadily declining to 7.3% (plasma bicarbonate 39 mmol/L) and 21.4% (eGFR 150 mL/min), respectively. To reach PTAs of ≥90% for pathogens with MICs ≥ 0.5 mg/L, optimized dosing regimens may be required.

Therapeutic Drug Monitoring of Antibiotics: Defining the Therapeutic Range

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

A personalised approach to antibiotic pharmacokinetics and pharmacodynamics in critically ill patients

Critically ill patients admitted to intensive care unit (ICU) with severe infections, or those who develop nosocomial infections, have poor outcomes with substantial morbidity and mortality. Such patients commonly have suboptimal antibiotic exposures at routinely used antibiotic doses related to an increased volume of distribution and altered clearance due to their underlying altered physiology. Furthermore, the use of extracorporeal devices such as renal replacement therapy and extracorporeal membrane oxygenation in these group of patients also has the potential to alter in vivo drug concentrations. Moreover, ICU patients are likely to be infected with less-susceptible pathogens. Therefore, one potential contributing cause to the poor outcomes observed in critically ill patients may be related to subtherapeutic antibiotic exposures. Newer concepts include the clinician considering optimised dosing based on a blood antibiotic exposure defined by pharmacokinetic modelling and therapeutic drug monitoring, combined with a knowledge of the antibiotic penetration into the site of infection, thereby achieving optimal bacterial killing. Such optimised dosing is likely to improve patient outcomes. The aim of this review is to highlight key aspects of antibiotic pharmacokinetics and pharmacodynamics (PK/PD) in critically ill patients and provide a PK/PD approach to tailor antibiotic dosing to the individual patient.

Drug-related problems of antibiotic use in gastroenteritis related to patient therapy outcomes at Universitas Gadjah Mada Hospital

OBJECTIVES

Gastroenteritis is a disease of digestive system commonly occur among the people. Some cases of gastroenteritis are caused by bacteria, so it is treated by using antibiotics. Inappropriate use of antibiotics can be associated to Drug-Related Problems (DRPs). This study aims to identify patterns of potential DRPs of antibiotic use and analyze the effect of potential DRPs of antibiotic use toward the patient's therapeutic outcomes and length of stay.

METHODS

This is a retrospective cross-sectional study carried out by using patient's medical record. The study population was gastroenteritis patients at the inpatient ward of Universitas Gadjah Mada Hospital during January 2018-June 2019. Then, SPSS was employed to analyze the data and the effect of potential DRPs toward therapeutic outcomes was analyzed by utilizing the chi-square method.

RESULTS

More than half of gastroenteritis patients in Universitas Gadjah Mada Hospital were identified to have potential DRPs of antibiotic use. The most identified of potential DRPs was problems related to drug selection. Based on the chi-square analysis, there was no relationship between potential DRPs of antibiotic use and the therapeutic outcome. In addition, there was also no relationship between potential DRPs of antibiotic use and patient's length of stay.

CONCLUSIONS

The potential DRPs of antibiotics use do not have a significant effect on the therapeutic outcome and length of stay of the gastroenteritis patients in Universitas Gadjah Mada Hospital.

Population pharmacokinetics of oral levofloxacin in healthy volunteers and dosing optimization for multidrug-resistant tuberculosis therapy

Levofloxacin is considered a key component of a multidrug-resistant tuberculosis (MDR-TB) regimen. However, there is considerable concern regarding the subtherapeutic concentrations of the currently used doses and the development of drug resistance. Therefore, this study aimed to describe the population pharmacokinetics (PPK) of oral levofloxacin in healthy volunteers and to evaluate the probability of target attainment (PTA) in an attempt to optimize the dosing regimens for MDR-TB therapy. Data of levofloxacin in healthy volunteers from a previous study were used to construct a PPK model. Monte Carlo simulations were performed to derive the PTAs of various regimens. A two-compartment model with linear elimination and transit absorption compartments best described the pharmacokinetics (PK) of levofloxacin. The estimated PK parameters (interindividual variability, %) were: apparent clearance 8.32 L h^-1 (22.6%), apparent central volume of distribution 35.8 L (45.2%), apparent peripheral volume of distribution 39.7 L, intercompartmental clearance 40.6 L h^-1 (43.8%), absorption rate constant 7.45 h^-1 (150%), mean absorption transit time 0.355 h (52.4%), and total number of transit compartments 6.01 (131.9%). Monte Carlo simulations using levofloxacin 750-1000 mg yielded a probability of achieving a target free area under the concentration-time curve/minimum inhibitory concentration (MIC) of 100 at greater than 90% for Mycobacterium tuberculosis with an MIC < 0.5 mg L^-1 , while a dose of 1500 mg was required for strains with an MIC of 1 mg L^-1 . A higher dose of levofloxacin might be needed to treat tuberculosis. However, further studies on the efficacy and safety of this dose are needed to confirm our findings.

Approach to the Treatment of Patients with Serious Multidrug-Resistant Pseudomonas aeruginosa Infections

Multidrug resistance(MDR) among Pseudomonas aeruginosa (PSA) isolates presents a significant clinical challenge and can substantially complicate the approach to selection of optimal antibiotic therapy. This review addresses major considerations in antibiotic selection for patients with suspected or documented serious MDR-PSA infections. Common mechanisms contributing to MDR among clinical PSA isolates are summarized. Empiric and definitive therapy considerations are addressed including the potential role of combination therapy. Newer agents with in vitro activity against MDR-PSA (e.g., ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam, and cefiderocol) and their potential roles in clinical settings are discussed. Although these newer agents are promising options for the treatment of MDR-PSA, clinical data remain generally limited. Future studies are needed to determine optimal agents for the empiric and definitive treatment of MDR-PSA.

Influence of Renal Function and Age on the Pharmacokinetics of Levofloxacin in Patients with Bone and Joint Infections

Despite its efficacy and toxicity being exposure-related, levofloxacin pharmacokinetics in patients with bone and joint infections has been poorly described to date, so the possible need for a dose adjustment is unknown in this population. A prospective population pharmacokinetic study was conducted in 59 patients to answer this question. The final model consisted of a one-compartment model with first-order absorption and elimination. Mean parameter estimates (% interindividual variability) were 0.895 h^-1 for the absorption rate constant (Ka), 6.10 L/h (40%) for the apparent clearance (CL/F), 90.6 L (25%) for the apparent distribution volume (V/F). Age and glomerular filtration rate (GFR), estimated by the modification of diet in renal disease formula, were related to CL/F by power models, and CL/F was found to increase for increasing GFR and decreasing age. For a similar GFR, the simulated area under the curve (AUC) was 55% higher in 70 years-old patients compared to 30 year-old patients. Based on this model, a 750 mg dose should provide an optimal exposure (AUC/ minimum inhibitory concentration (MIC) ≥100), with the possible exception of patients older than 60 years and with GFR <70 mL/min/m² who may necessitate a dose reduction, and patients with infections caused by bacteria with MIC close to 1 mg/L who may need an increase in the dose.

Pharmacokinetics and pharmacodynamics of levofloxacin in bronchial mucosa and lung tissue of patients undergoing pulmonary operation

Levofloxacin is a major antimicrobial agent that is used for the treatment of community-acquired lower respiratory tract infections (LRTIs). The present study was designed to investigate the pharmacokinetics (PK) and pharmacodynamics (PD) of levofloxacin in bronchial mucosa and lung tissue. A total of 32 patients undergoing pulmonary surgery were randomly assigned to one of four groups (8 subjects/group). All patients received a single dose of 500 mg levofloxacin orally prior to the operation. Blood, lung tissue and bronchial mucosa samples were collected prior to treatment and at 1.5, 4, 8, 12 and 24 h following treatment. The drug concentration was determined and PK and PD profiles were calculated using MATLAB software. The peak concentration of levofloxacin was 7.0±1.2 µg/g in lung tissues and 9.4±2.1 µg/g in bronchial mucosa. The corresponding area under the curve between 0 and 24 h (AUC0-24) was 85.7±8.5 and 137.3±19.4 µg h/g. The mean permeability of levofloxacin (ratio of concentration in tissue to that in plasma) was 2.4 in lung tissue and 4.4 in the bronchial mucosa. The PK profiles of levofloxacin in the plasma, lung and bronchial mucosa were described using an integrated one-compartment model. The probability of fAUC0-24/minimal inhibitory concentration (MIC) target attainment of levofloxacin against Streptococcus pneumoniae in the lung and bronchial mucosa was maintained at 100% when MIC ≤1 mg/l, while the cumulative fraction of fAUC0-24/MIC in the corresponding tissues was 94.4 and 98.1%, respectively. The present study demonstrated the high permeability of levofloxacin in the lung and bronchial mucosa of patients undergoing pulmonary surgery. In conclusion, treatment using 500 mg levofloxacin exhibits good clinical and microbiological efficacy for use in LRTIs that are caused by S. pneumoniae. This trial was registered retrospectively in the Chinese Clinical Trial Registry on January 13, 2020 (registration no. ChiCTR2000029096).

Considerations for the optimal management of antibiotic therapy in elderly patients

OBJECTIVES

To maximise efficacy and minimise toxicity, special considerations are required for antibiotic prescription in elderly patients. This review aims to provide practical suggestions for the optimal management of antibiotic therapy in elderly patients.

METHODS

This was a narrative review. A literature search of published articles in the last 15 years on antibiotics and elderly patients was performed using the Cochrane Library and PubMed electronic databases. The three priority areas were identified: (i) pharmacokinetics/pharmacodynamics (PK/PD) for optimising dosage regimens and route of administration; (ii) antibiotic dosages in some special subpopulations; and (iii) treatment considerations relating to different antibiotic classes and their adverse events.

RESULTS

Clinicians should understand the altered PK/PD of drugs in this population owing to co-morbid conditions and normal physiological changes associated with ageing. The body of evidence justifies the need for individualised dose selection, especially in patients with impaired renal and liver function. Clinicians should be aware of the major drug-drug interactions commonly observed in the elderly as well as potential side effects.

CONCLUSION

Antibiotic therapy in the elderly requires a comprehensive approach, including strategies to improve appropriate antibiotic prescribing, limit their use for uncomplicated infections and ensure the attainment of an optimal PK/PD target. To this purpose, further studies involving the elderly are needed to better understand the PK of antibiotics. Moreover, it is necessary to assess the role therapeutic drug monitoring in guiding antibiotic therapy in elderly patients in order to evaluate its impact on clinical outcome.