Intracellular Pharmacokinetics of Antibacterials and Their Clinical Implications

Have We Neglected to Study Target-Site Drug Exposure in Children? A Systematic Review of the Literature

BACKGROUND AND OBJECTIVE

Drug dosing should ideally be based on the drug concentrations at the target site, which, for most drugs, corresponds to the tissue. The exact influence of growth and development on drug tissue distribution is unclear. This systematic review compiles the current knowledge on the tissue distribution of systemically applied drugs in children, with the aim to identify priorities in tissue pharmacokinetic (PK) research in this population.

METHODS

A systematic literature search was performed in the MEDLINE and Embase databases.

RESULTS

Forty-two relevant articles were identified, of which 71% investigated antibiotics, while drug classes from the other studies were anticancer drugs, antifungals, anthelmintics, sedatives, thyreostatics, immunomodulators, antiarrhythmics, and exon skipping therapy. The majority of studies (83%) applied tissue biopsy as the sampling technique. Tonsil and/or adenoid tissue was most frequently examined (70% of all included patients). The majority of studies had a small sample size (median 9, range 1-93), did not include the youngest age categories (neonates and infants), and were of low reporting quality. Due to the heterogeneous data from different study compounds, dosing schedules, populations, and target tissues, the possibility for comparison of PK data between studies was limited.

CONCLUSION

The influence of growth and development on drug tissue distribution continues to be a knowledge gap, due to the paucity of tissue PK data in children, especially in the younger age categories. Future research in this field should be encouraged as techniques to safely investigate drug tissue disposition in children are available.

Improving ADMET Prediction Accuracy for Candidate Drugs: Factors to Consider in QSPR Modeling Approaches

Quantitative Structure-Property Relationship (QSPR) employs mathematical and statistical methods to reveal quantitative correlations between the pharmacokinetics of compounds and their molecular structures, as well as their physical and chemical properties. QSPR models have been widely applied in the prediction of drug absorption, distribution, metabolism, excretion, and toxicity (ADMET). However, the accuracy of QSPR models for predicting drug ADMET properties still needs improvement. Therefore, this paper comprehensively reviews the tools employed in various stages of QSPR predictions for drug ADMET. It summarizes commonly used approaches to building QSPR models, systematically analyzing the advantages and limitations of each modeling method to ensure their judicious application. We provide an overview of recent advancements in the application of QSPR models for predicting drug ADMET properties. Furthermore, this review explores the inherent challenges in QSPR modeling while also proposing a range of considerations aimed at enhancing model prediction accuracy. The objective is to enhance the predictive capabilities of QSPR models in the field of drug development and provide valuable reference and guidance for researchers in this domain.

The Association of Serotonin Toxicity with Combination Linezolid-Serotonergic Agent Therapy: A Systematic Review and Meta-Analysis

Linezolid (LZD) has a longstanding reported association with the onset of serotonin toxicity (ST), secondary to drug-drug interactions with serotoninergic agents. There have been no conclusive data supporting the incidence or contributing risk factors to date. The study evaluated the incidence of ST in patients treated with LZD and serotonergic agents concomitantly versus LZD alone. The secondary objectives included a comparison of ST incidence in patients treated with one serotonergic agent + LZD versus two or more serotonergic agents + LZD. The studies used for this meta-analysis were retrieved from PubMed, Scopus, and Google Scholar. All studies including a comparison between LZD alone and LZD + a serotonergic agent published between 1 January 2000 and 1 October 2023 and meeting the quality standards were considered for inclusion. Fourteen studies were identified, with five meeting all inclusion and exclusion criteria with no significant heterogeneity. For the analysis of LZD monotherapy vs. SA combination therapy, four studies with 6025 patients total were analyzed and yielded an odds ratio of 1.78 (CI [1.04, 3.02]; I2 = 49%; GRADE certainty: low). Four studies and 2501 patients were included in the analysis of one versus more than one SA with an odds ratio of 5.18 (CI [1.05, 25.49]; I2 = 44.87; GRADE certainty: moderate). The Newcastle-Ottawa score, visual inspection of the funnel plot, and Egger's statistic were used to evaluate quality and heterogeneity. The Peto method was used to calculate the summary odds ratios. All analyses were performed using Comprehensive Meta-Analysis version 3.0 and R, while GRADE was used to evaluate the quality of the final recommendation. The number of concomitant serotonergic agents may play a role in the development of serotonin toxicity in patients prescribed linezolid. In patients requiring linezolid therapy and serotonergic agents, risk versus benefit analysis should pay attention to the number of interacting drugs.

Translatability of in vitro potency to clinical efficacious exposure: A retrospective analysis of FDA-approved targeted small molecule oncology drugs

In vitro potency is one of the important parameters representing efficacy potential of drugs and commonly used as benchmark of efficacious exposure at early clinical development. There are limited numbers of studies which systematically investigate on how predictive in vitro potency is to estimate therapeutic drug exposure, especially those focusing on targeted anticancer agents despite the recent increase in approvals. This study aims to fill in such knowledge gaps. A total of 87 small molecule targeted drugs approved for oncology indication between 2001 and 2020 by the US Food and Drug Administration (FDA) were identified; relevant preclinical and clinical data were extracted from the public domain. Relationships between the in vitro potency and the therapeutic dose or exposure (unbound average drug concentration [Cu,av ] as the primary exposure metrics) were assessed by descriptive analyses. The Spearman's rank correlation test showed slightly better correlation of the Cu,av (ρ = 0.232, p = 0.041) rather than the daily dose (ρ = 0.186, p = 0.096) with the in vitro potency. Better correlation was observed for the drugs for hematologic malignancies compared with those for solid tumors (root mean square error: 140 [n = 28] versus 297 [n = 59]). The present study shows that in vitro potency is predictive to estimate the therapeutic drug exposure to some extent, whereas the general trend of overexposure was observed. The results suggested that in vitro potency alone is not sufficient and robust enough to estimate the clinically efficacious exposure of molecularly targeted small molecule oncology drugs. The totality of data, including both nonclinical and clinical, needs to be considered for dose optimization.

Therapeutic drug monitoring of disease-modifying antirheumatic drugs in circulating leukocytes in immune-mediated inflammatory diseases

The treatment of immune-mediated inflammatory diseases (IMIDs) is one of the main challenges of modern medicine. Although a number of disease-modifying antirheumatic drugs (DMARDs) are available, there is wide variability in clinical response to treatment among individuals. Therapeutic drug monitoring (TDM) has been proposed to optimize treatment; however, some patients still experience unsatisfactory outcomes, although the blood concentrations of drugs in these patients remain in the therapeutic range. One possible reason for this is that the conventional samples (e.g., whole blood or plasma) used in TDM may not accurately reflect drug concentrations or concentrations of their metabolites at the target site. Hence, more refined TDM approaches to guide clinical decisions related to dose optimization are necessary. Circulating leukocytes or white blood cells have a critical role in driving the inflammatory process. They are recruited to the site of injury, infection and inflammation, and the main target of small molecule DMARDs is within immune cells. Given this, assaying drug concentrations in leukocytes has been proposed to be of possible relevance to the interpretation of outcomes. This review focuses on the clinical implications and challenges of drug monitoring of DMARDs in peripheral blood leukocytes from therapeutic or toxicological perspectives in IMIDs.

Misunderstandings and misinterpretations: Antimicrobial use and resistance in salmon aquaculture

The exponential growth of aquaculture over the past 30 years has been accompanied by a parallel increase in the use of antimicrobials. This widespread use has had negative effects on animal, human and environmental health and affected the biodiversity of the environments where aquaculture takes place. Results showing these harmful effects have been resisted and made light of by the aquaculture industry and their scientific supporters through introduction of misunderstandings and misinterpretations of concepts developed in the evolution, genetics, and molecular epidemiology of antimicrobial resistance. We focus on a few of the most obvious scientific shortcomings and biases of two recent attempts to minimise the negative impacts of excessive antimicrobial use in Chilean salmon aquaculture on human and piscine health and on the environment. Such open debate is critical to timely implementation of effective regulation of antimicrobial usage in salmon aquaculture in Chile, if the negative local and worldwide impacts of this usage are to be avoided.

The Use of Antibiotics and Antimicrobial Resistance in Veterinary Medicine, a Complex Phenomenon: A Narrative Review

As warned by Sir Alexander Fleming in his Nobel Prize address: “the use of antimicrobials can, and will, lead to resistance”. Antimicrobial resistance (AMR) has recently increased due to the overuse and misuse of antibiotics, and their use in animals (food-producing and companion) has also resulted in the selection and transmission of resistant bacteria. The epidemiology of resistance is complex, and factors other than the overall quantity of antibiotics consumed may influence it. Nowadays, AMR has a serious impact on society, both economically and in terms of healthcare. This narrative review aimed to provide a scenario of the state of the AMR phenomenon in veterinary medicine related to the use of antibiotics in different animal species; the impact that it can have on animals, as well as humans and the environment, was considered. Providing some particular instances, the authors tried to explain the vastness of the phenomenon of AMR in veterinary medicine due to many and diverse aspects that cannot always be controlled. The veterinarian is the main reference point here and has a high responsibility towards the human–animal–environment triad. Sharing such a burden with human medicine and cooperating together for the same purpose (fighting and containing AMR) represents an effective example of the application of the One Health approach.

Positive Association Between Fluoroquinolone Exposure and Tendon Disorders: A Nationwide Population-Based Cohort Study in Taiwan

Introduction: Fluoroquinolone exposure is reportedly associated with a higher risk of tendon disorders, tendonitis, or tendon rupture. However, studies in East Asian populations have not confirmed these risks in patients with comorbidities or concomitant medication use. This cohort study was designed to investigate the associations among fluoroquinolone exposure, comorbidities, medication use, and tendon disorders in Taiwan.

Materials and Methods: This population-based, nationwide, observational, cohort study used data from the National Health Insurance Research database in Taiwan, a nationwide claims database that covers more than 99% of the Taiwanese population. The study period was from January 2000 to December 2015, and the median follow-up time was 11.05 ± 10.91 years. Patients who were exposed to fluoroquinolones for more than three consecutive days were enrolled, and patients without fluoroquinolone exposure who were matched by age, sex, and index year were enrolled as controls. The associations of comorbidities and concomitant medication use with tendon disorder occurrence were analyzed using Cox regression models.

Results: The incidence of tendon disorders were 6.61 and 3.34 per 10⁵ person-years in patients with and without fluoroquinolone exposure, respectively (adjusted hazard ratio, 1.423; 95% confidence interval [1.02,1.87]; p = 0.021). Sensitivity analyses yielded similar results. Patients under 18 and over 60 years with fluoroquinolone exposure; those with chronic kidney disease, diabetes, rheumatologic disease, cardiac disease, lipid disorder, or obesity; and those who concomitantly used statins, aromatase inhibitors, or glucocorticoids, had a significantly higher risk of tendon disorders.

Conclusion: The long-term risk of tendon disorders was higher in patients with fluoroquinolone exposure than in those without fluoroquinolone exposure. Clinicians should assess the benefits and risks of fluoroquinolone use in patients at high risk of tendon disorders who require fluoroquinolone administration.

Chinese ICU physicians' knowledge of antibiotic pharmacokinetics/pharmacodynamics (PK/PD): a cross-sectional survey

BACKGROUND

Patients with sepsis have a high mortality rate, accumulated evidences suggest that an optimal antibiotic administration strategy based on pharmacokinetics/pharmacodynamics (PK/PD) can improve the prognosis of septic patients. Therefore, we assessed Chinese intensive care unit (ICU) physicians' knowledge about PK/PD.

METHODS

In December 2019, we designed a questionnaire focused on Chinese ICU physicians' knowledge about PK/PD and collected the questionnaires after 3 months. The questionnaire was distributed via e-mail and WeChat, and was distributed to ICU doctors in 31 administrative regions of China except Hong Kong, Macao and Taiwan. The passing score was corrected by the Angoff method, and the ICU physicians' knowledge about PK/PD was analysed accordingly.

RESULTS

We received a total of 1,309 questionnaires and retained 1,240 valid questionnaires. The passing score was 90.8, and the overall pass rate was 56.94%. The pass rate for tertiary and secondary hospitals was 59.07% and 37.19%, respectively. ICU physicians with less than 5 years of work experience and resident physician accounted for the highest pass rate, while those with between 5 to 10 years of work experience and attending accounted for the lowest pass rate. The majority of participants in the Chinese Critical Care Certified Course (5C) were from Jiangsu and Henan provinces, and they had the highest average scores (125.8 and 126.5, respectively). For Beijing and Shanghai, the average score was only 79.4 and 90.9, respectively.

CONCLUSIONS

Chinese ICU physicians' knowledge about PK/PD is unsatisfactory. Therefore, it is essential to strengthen ICU physicians' knowledge about PK/PD.

Splenic macrophages as the source of bacteraemia during pneumococcal pneumonia

Background

Severe community-acquired pneumococcal pneumonia is commonly associated with bacteraemia. Although it is assumed that the bacteraemia solely derives from pneumococci entering the blood from the lungs it is unknown if other organs are important in the pathogenesis of bacteraemia. Using three models, we tested the relevance of the spleen in pneumonia-associated bacteraemia.

Methods

We used human spleens perfused ex vivo to explore permissiveness to bacterial replication, a non-human primate model to check for splenic involvement during pneumonia and a mouse pneumonia-bacteraemia model to demonstrate that splenic involvement correlates with invasive disease.

Findings

Here we present evidence that the spleen is the reservoir of bacteraemia during pneumonia. We found that in the human spleen infected with pneumococci, clusters with increasing number of bacteria were detectable within macrophages. These clusters also were detected in non-human primates. When intranasally infected mice were treated with a non-therapeutic dose of azithromycin, which had no effect on pneumonia but concentrated inside splenic macrophages, bacteria were absent from the spleen and blood and importantly mice had no signs of disease.

Interpretation

We conclude that the bacterial load in the spleen, and not lung, correlates with the occurrence of bacteraemia. This supports the hypothesis that the spleen, and not the lungs, is the major source of bacteria during systemic infection associated with pneumococcal pneumonia; a finding that provides a mechanistic basis for using combination therapies including macrolides in the treatment of severe community-acquired pneumococcal pneumonia.

Funding

Oxford University, Wolfson Foundation, MRC, NIH, NIHR, and MRC and BBSRC studentships supported the work.

Intra-tracheal administration increases gallium availability in lung: implications for antibacterial chemotherapy

The emergence of pan-resistant strains in nosocomial settings underscores the urgent need of novel therapies targeting vital bacterial functions. Bacterial iron metabolism is a fascinating target for new antimicrobials. Iron mimetic metal Ga(III) has been repurposed as an antimicrobial drug, in pre-clinical studies and recent clinical studies have raised the possibility of using Ga(III) for the treatment of P. aeruginosa pulmonary infection. Ga(III) has been approved by FDA for the treatment of cancer, autoimmune and bone resorption disorders. However, some critical issues affect the therapeutic schedule of Ga(III), principally the intra-venous (i.v.) administration, and the nephrotoxicity caused by prolonged administration. Ga(III) aerosolization could represent a viable alternative for treatment of lung infections, since delivery of antimicrobial agents to the airways maximizes drug concentration at the site of infection, improves the therapeutic efficacy, and alleviates systemic toxic effects. We demonstrate the advantage of inhaled vs i.v. administered Ga(III), in terms of bio-distribution and lung acute toxicity, by using a rat model. In vivo results support the use of Ga(III) for inhalation since intra-tracheal Ga(III) delivery improved its persistence in the lung, while the i.v. administration caused rapid clearance and did not allow to attain a significant Ga(III) concentration in this organ. Moreover, local and systemic acute toxicity following intra-tracheal administration was not observed, since no significant signs of inflammation were found. At this stage of evidence, the direct administration of Ga(III) to the lung appears feasible and safe, boosting the development of Ga(III)-based drugs for inhalation therapy.

Gold nanoclusters treat intracellular bacterial infections: Eliminating phagocytic pathogens and regulating cellular immune response

Intracellular bacterial infection is underlying many serious human disorders, leading to high morbidity and mortality. The development of safe and efficient therapeutic agents is the most effective solutions to combat intracellular bacterial infections. Recently, ultrasmall gold nanoclusters (AuNCs) have emerged as an innovative nanoantibiotics against multidrug-resistant bacterial infections due to their inherent antibacterial activity. However, the therapeutic effects of AuNCs on intracellular bacterial infections and their effects on host cells still remain unvisited. Here, we demonstrate the therapeutic potential of 4,6-diamino-2-mercaptopyrimidine-functionalized AuNCs (AuDAMP) for intracellular multidrug-resistant infections in a co-culture model of macrophages and methicillin-resistant Staphylococcus aureus (MRSA). The AuNCs were found to show a superior intracellular antibacterial capability, which can eliminate most of the MRSA phagocytosed by macrophages, and without exhibiting obvious cytotoxicity on host RAW 264.7 macrophages at tested concentrations. More importantly, treatment of AuDAMP exerts critical roles on enhancing the innate immune response to defend against pathogens invading inside the host cells and alleviating the bacterial infection-induced inflammatory response to avoid pyroptosis by up-regulating significantly xenophagy level in macrophages. Taken together, our results suggest that AuNCs hold great potential for the treatment of intracellular bacterial infections.

Systematic review: the bioavailability of orally administered antibiotics during the initial phase of a systemic infection in non-ICU patients

Background

The systemic response to an infection might influence the pharmacokinetics of antibiotics. To evaluate the desired possibility of an earlier (< 24 h) IV-to-oral switch therapy in febrile non-ICU, hospitalized patients, a systematic review was performed to assess the effect of the initial phase of a systemic infection on the bioavailability of orally administered antibiotics in such patients.

Methods

An electronic search was conducted in MEDLINE and Embase up to July 2020. Studies were selected when outcome data were collected during the initial stage of a febrile disease. Outcome data were (maximum) serum concentrations, time of achieving maximum serum concentration, and the area-under-the-plasma-concentration-time curve or bioavailability of orally administered antibiotics. Risk of bias was assessed.

Results

We identified 9 studies on 6 antibiotics. Ciprofloxacin was the most frequently studied drug. Outcomes of the studies were heterogeneous and generally had a high risk of bias. Three small studies, two on ciprofloxacin and one on clarithromycin, compared the pharmacokinetics of febrile patients with those of clinically recovered patients and suggested that bioavailability was not altered in these patients. Other studies either compared the pharmacokinetics in febrile patients with reported pharmacokinetic values from earlier studies in healthy volunteers (n = 2), or provided no comparison at all and were non-conclusive (n = 4).

Conclusion

There is a clear knowledge gap regarding the bioavailability of orally administered antibiotics in non-ICU patients during the initial phase of a systemic infection. Well-designed studies on this topic are necessary to elucidate whether patients can benefit from the advantages of an earlier IV-to-oral switch.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-05919-w.

Serotonin syndrome by drug interactions with linezolid: clues from pharmacovigilance-pharmacokinetic/pharmacodynamic analysis

Purpose

To characterize the post-marketing reporting of serotonin syndrome (SS) due to drug-drug interactions (DDIs) with linezolid and investigate the relationship with pharmacokinetic/pharmacodynamic (PK/PD) properties of serotonergic agents.

Methods

We queried the worldwide FDA Adverse Event Reporting System to extract SS records due to DDIs where linezolid was reported as suspect. For each serotonergic agent concomitantly reported, proportion of SS reports and mean number of DDIs were calculated and three different “SS reporting zones” were created. Relevant PK (peak concentration, area under plasma concentration curve, volume of distribution (V_D), and lipophilicity) and PD (values of binding affinity (Ki) and IC₅₀ for serotonin reuptake transporter (SERT) and 5-HT_2A) parameters were extracted for each serotonergic agent, and relevant PK/PD indexes were calculated to assess correlation with mean number of DDIs (PV index).

Results

Six hundred sixty-nine reports of SS mentioning linezolid were found, being linezolid-citalopram (N = 69; 10.3%) the most frequently DDI reported. Citalopram and methadone showed respectively the highest proportion of SS reports (0.28%) and the lowest mean number of DDIs (1.41). Citalopram, escitalopram, and methadone emerged as red (i.e., alert)-zone medications: they exhibited high lipophilicity and large V_D (proxies of excellent central nervous system penetration) coupled with high potency. Among PK/PD indexes, a significant correlation with PV index was found for V_D/Ki SERT ratio (p = 0.05).

Discussion

Our integrated approach suggests that linezolid is more likely to cause SS when co-administered with citalopram, escitalopram, and methadone, as inferred from their pharmacological properties. Proper management of SS should be tailored on a case-by-case basis.

Electronic supplementary material

The online version of this article (10.1007/s00228-020-02990-1) contains supplementary material, which is available to authorized users.

Pharmacokinetic/pharmacodynamic considerations for new and current therapeutic drugs for uncomplicated gonorrhoea-challenges and opportunities

BACKGROUND

Increasing multidrug resistance rates in Neisseria gonorrhoeae have raised concerns and an urgent call for new antibiotics for treatment of gonorrhoea. Several decades of subdued drug development in this field and the recent failures of two new antibiotics to show non-inferiority compared with the current first-line antibiotics ceftriaxone plus azithromycin highlight the need for improved preclinical tools to predict clinical outcome of new drugs in the development process.

OBJECTIVES

To summarize current pharmacokinetic/pharmacodynamic (PK/PD) knowledge and dose-finding strategies for antibiotics against gonorrhoea.

SOURCES

Literature review of published papers and discussions by global experts at a special workshop on this topic.

CONTENT

We review current knowledge of gonococcal specific PK/PD principles and provide an update on new in vitro and in vivo models to correlate drug exposure with clinical outcome, and identify challenges and gaps in gonococcal therapeutic research.

IMPLICATIONS

Identifying the ideal antimicrobial agent and dose for treating uncomplicated urogenital and pharyngeal gonococcal disease requires appropriate validated non-clinical PK/PD models. Recent advances in adapting in vitro and in vivo models for use in gonorrhoea are an important step for enabling the development of new drugs with reduced risk of failure in Phase 3 clinical development and diminish the risk of emergence of resistance.

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).

Does In Vitro Potency Predict Clinically Efficacious Concentrations?

The in vitro affinity of a compound for its target is an important feature in drug discovery, but what remains is how predictive in vitro properties are of in vivo therapeutic drug exposure. We assessed the relationship between in vitro potency and clinically efficacious concentrations for marketed small molecule drugs (n = 164) and how they may differ depending on therapeutic indication, mode of action, receptor type, target localization, and function. Approximately 70% of compounds had a therapeutic unbound plasma exposure lower than in vitro potency; the median ratio of exposure in relation to in vitro potency was 0.32, and 80% had ratios within the range of 0.007 to 8.7. We identified differences in the in vivo–to–in vitro potency ratio between indications, mode of action, target type, and matrix localization, and whether or not the drugs had active metabolites. The in vitro–assay variability contributions appeared to be the smallest; within the same drug target and mode of action the within‐variability was slightly broader; but both were substantially less compared with the overall distribution of ratios. These data suggest that in vitro potency conditions, estimated in vivo potency, required level of receptor occupancy, and target turnover are key components for further understanding the link between clinical drug exposure and in vitro potency.

The management of anti-infective agents in intensive care units: the potential role of a 'fast' pharmacology

INTRODUCTION

Patients in intensive care units (ICU) are often developing severe infections in which are associated with significant mortality rates. A number of novel technologies for the rapid microbiological diagnosis of these infections have been developed, introducing the era of 'fast microbiology.' Treatment of bacterial and fungal infections in ICU is however complicated by alterations in the pharmacokinetics of antimicrobial agents.

AREAS COVERED

We review novel pharmacologic tools that can be used to optimize anti-infective therapies and patient management in ICU. A MEDLINE Pubmed search for articles published from January 1995 to 2019 was completed matching the terms pharmacokinetics and pharmacology with antimicrobial agents and ICU or critically ill patients. Moreover, additional studies were identified from the reference list of retrieved articles.

EXPERT OPINION

Several tools are in development for the full automation of the analytical methods used for the quantification of antimicrobial concentrations within a few hours after sample collection. Ad hoc software with adaptive feedback is also available for appropriate dose adjustments based on both individual patient covariate data and therapeutic drug monitoring (TDM) data when available. The application of these technological improvements in the clinical practice should open the way to a 'fast pharmacology' at the bedside.

Generation of new hair cells by DNA methyltransferase (Dnmt) inhibitor 5-azacytidine in a chemically-deafened mouse model

Regeneration of mature mammalian inner ear hair cells remains to be a challenge. This study aims to evaluate the ability of DNA methyltransferase (Dnmt) inhibitor 5-azacytidine (5-aza) to generate outer hair cells (OHCs) in a chemically-deafened adult mouse model. 5-aza was administrated into the mouse inner ear via the round window. Immunofluorescence was used to examine the expression of hair cell specific proteins following 5-aza treatment. The results showed that in the chemically-deafened mouse cochlea, new OHCs were found post 5-aza treatment, whereas OHCs were completely lost in saline-treated mice. New hair cells expressed multiple hair cell markers included Myosin VIIa, Pou4f3 and Myosin VI. Newly-generated hair cells presented in three cochlear turns and were able to survive for at least six weeks. The effects of new hair cells generation by 5-aza were concentration dependent. Quantitative PCR study indicates that 5-aza may function through Dnmt1 inhibition. The results of this report suggest that the Dnmt inhibitor 5-aza may promote hair cell regeneration in a chemically-deafened mouse model.

Population Pharmacokinetics and Dosing Optimization of Azithromycin in Children with Community-Acquired Pneumonia

Azithromycin is extensively used in children with community-acquired pneumonia (CAP). Currently, the intravenous azithromycin is used off-label in children partly due to lacking of pharmacokinetic data. Our objective was to evaluate the population pharmacokinetics (PPK) and optimize dose strategy in order to improve treatment in this distinctive population. This was a prospective, multicenter, open-labeled pharmacokinetic study. Blood samples were collected from hospitalized pediatric patients and concentrations were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). PPK analysis was conducted using NONMEM software. The pharmacokinetic data from 95 pediatric patients (age range, 2.1 to 11.7 years) were available for analysis. The PPK was best fitted by a two-compartment model with linear elimination. Covariate analysis verified that body weight and alanine aminotransferase (ALT) had significant effects on azithromycin pharmacokinetics, yielding a 24% decrease of clearance in patients with ALT of >40. Monte Carlo simulation showed that for children with normal liver function, a loading-dose strategy (a loading dose of 15 mg/kg of body weight followed by maintenance doses of 10 mg/kg) would achieve the ratio of the area under free drug plasma concentration-time curve over 24 h (fAUC) to MIC₉₀ (fAUC/MIC) target of 3 h in 53.2% of hypothetical patients, using a normative MIC susceptibility breakpoint of 2 mg/liter. For children with ALT of >40, the proposed dose needed to decrease by 15% to achieve comparable exposure. The corresponding risk of overdose for the recommended dosing regimen was less than 5.8%. In conclusion, the PPK of azithromycin was evaluated in children with CAP and an optimal dosing regimen was constructed based on developmental pharmacokinetic-pharmacodynamic modeling and simulation.