Aminoglycoside nephrotoxicity: modeling, simulation, and control

Polyvinyl alcohol electrospun nanofiber membrane based solid-phase extraction for monitoring administered aminoglycoside antibiotics in various animal-derived foods

This work aims to develop a widely applicable method to monitor administered AGs in various animal-derived food samples to ensure food safety. A polyvinyl alcohol electrospun nanofiber membrane (PVA NFsM) was synthesized and employed as solid-phase extraction (SPE) sorbent, in combination with UPLC-MS/MS, for the simultaneous detection of ten AGs in nine types of animal-derived food samples. PVA NFsM exhibited excellent adsorption performance for the targets (with an adsorption rate of over 91.09%), good matrix purification ability (with a reduction of 7.65%-77.47% in matrix effect after SPE), and good recyclability (can be reused 8 times). The method displayed a linear range of 0.1-25000 μg/kg and attained limits of detection for AGs were 0.03-15 μg/kg. Spiked samples demonstrated a recovery of 91.72%-100.04% with a precision of<13.66%. The practicality of the developed method was verified by testing multiple actual samples.

Implementation of Model-Based Dose Adjustment of Tobramycin in Adult Patients with Cystic Fibrosis

Therapeutic drug monitoring (TDM) of tobramycin is widely performed in patients with cystic fibrosis (CF), but little is known about the value of model-informed precision dosing (MIPD) in this setting. We aim at reporting our experience with tobramycin MIPD in adult patients with CF. We analyzed data from adult patients with CF who received IV tobramycin and had model-guided TDM during the first year of implementation of MIPD. The predictive performance of a pharmacokinetic (PK) model was assessed. Observed maximal (Cmax) and minimal (Cmin) concentrations after initial dosing were compared with target values. We compared the initial doses and adjusted doses after model-based TDM, as well as renal function at the beginning and end of therapy. A total of 78 tobramycin courses were administered in 61 patients. After initial dosing set by physicians (mean, 9.2 ± 1.4 mg/kg), 68.8% of patients did not achieve the target Cmax ≥ 30 mg/L. The PK model fit the data very well, with a median absolute percentage error of 4.9%. MIPD was associated with a significant increase in tobramycin doses (p < 0.001) without significant change in renal function. Model-based dose suggestions were wellaccepted by the physicians and the expected target attainment for Cmax was 83%. To conclude, the implementation of MIPD was effective in changing prescribing practice and was not associated with nephrotoxic events in adult patients with CF.

Mathematical Modeling for an MTT Assay in Fluorine-Containing Graphene Quantum Dots

The paper reports on a new mathematical model, starting with the original Hill equation which is derived to describe cell viability (V) while testing nanomaterials (NMs). Key information on the sample's morphology, such as mean size (⟨s⟩) and size dispersity (σ) is included in the new model via the lognormal distribution function. The new Hill-inspired equation is successfully used to fit MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) data from assays performed with the HepG2 cell line challenged by fluorine-containing graphene quantum dots (F:GQDs) under light (400-700 nm wavelength) and dark conditions. The extracted "biological polydispersity" (light: ⟨sMTT⟩=1.77±0.02&nbsp;nm and σMTT=0.21±0.02); dark: ⟨sMTT⟩=1.87±0.02&nbsp;nm and σMTT=0.22±0.01) is compared with the "morphological polydispersity" (⟨sTEM⟩=1.98±0.06&nbsp;nm and σTEM=0.19±0.03), the latter obtained from TEM (transmission electron microscopy). The fitted data are then used to simulate a series of V responses. Two aspects are emphasized in the simulations: (i) fixing σ, one simulates V versus ⟨s⟩ and (ii) fixing ⟨s⟩, one simulates V versus σ. Trends observed in the simulations are supported by a phenomenological model picture describing the monotonic reduction in V as ⟨s⟩ increases (V~pa/(s)p-a; p and a are fitting parameters) and accounting for two opposite trends of V versus σ: under light (V~σ) and under dark (V~1/σ).

Pharmacokinetic modelling to predict risk of ototoxicity with intravenous tobramycin treatment in cystic fibrosis

INTRODUCTION

Further optimization of therapeutic drug monitoring (TDM) for aminoglycosides (AGs) is urgently needed, especially in special populations such as those with cystic fibrosis (CF), >50% of whom develop ototoxicity if treated with multiple courses of IV AGs. This study aimed to empirically test a pharmacokinetic (PK) model using Bayesian estimation of drug exposure in the deeper body tissues to determine feasibility for prediction of ototoxicity.

MATERIALS AND METHODS

IV doses (n = 3645) of tobramycin and vancomycin were documented with precise timing from 38 patients with CF (aged 8-21 years), including total doses given and total exposure (cumulative AUC). Concentration results were obtained at 3 and 10 h for the central (C1) compartment. These variables were used in Bayesian estimation to predict trough levels in the secondary tissue compartments (C2 trough) and maximum concentrations (C2max). The C1 and C2 measures were then correlated with hearing levels in the extended high-frequency range.

RESULTS

Patients with more severe hearing loss were older and had a higher number of tobramycin C2max concentrations >2 mg/L than patients with normal or lesser degrees of hearing loss. These two factors together significantly predicted average high-frequency hearing level (r = 0.618, P < 0.001). Traditional metrics such as C1 trough concentrations were not predictive. The relative risk for hearing loss was 5.8 times greater with six or more tobramycin courses that exceeded C2max concentrations of 3 mg/L or higher, with sensitivity of 83% and specificity of 86%.

CONCLUSIONS

Advanced PK model-informed analysis predicted ototoxicity risk in patients with CF treated with tobramycin and demonstrated high test prediction.

Adverse effects induced by second-line antituberculosis drugs: an update based on last WHO treatment recommendations for drug-resistant tuberculosis

Introduction: Tuberculosis (TB), a common condition worldwide, is still among the main infectious diseases with high mortality rates, both in adults and infants. Drug-resistant tuberculosis (DR-TB) drugs, revised by the World Health Organization (WHO) in 2018, are a prolonged and complex therapy associated with many adverse drug effects (ADEs).

Aim: To systematically review the ADEs of second-line anti-TB drugs reported in multicentric studies published after the latest WHO guidelines, compared with those from clinical trials published before 2018.

Material and methods: A PubMed search, using keywords (TB OR DR-TB) AND (adverse effects) AND “second-line anti-TB drugs”, resulted in 56 studies. Only two studies, published after the last update of WHO guidelines in 2018, reported ADEs.

Results: A total of 223 participants were included in the two selected studies. The use of multidrug regimens has been associated with an increased incidence of ADEs: 42 ADEs were recorded in 30 patients (26.3%) in the first study, while all patients had at least one ADE that occurred or worsened during treatment; and 19 (17%) had severe ADEs in the second study. However, both studies had a good favourable outcome rate (90% and 79.8%, respectively). Gastrointestinal disturbances, hepatotoxicity, headache and dizziness are the most common ADEs induced by a majority of second-line DR-TB treatments. A special attention should be given in the case of association of drugs determining QT interval (QT) prolongation on electrocardiogram, or psychiatric disorders.

Conclusions: Proper strategies about ADE management have to be planned for timely detection of the possible ADEs that can be induced by second-line anti-TB therapy.

Structural and phylogenetic analyses of resistance to next-generation aminoglycosides conferred by AAC(2') enzymes

Plazomicin is currently the only next-generation aminoglycoside approved for clinical use that has the potential of evading the effects of widespread enzymatic resistance factors. However, plazomicin is still susceptible to the action of the resistance enzyme AAC(2')-Ia from Providencia stuartii. As the clinical use of plazomicin begins to increase, the spread of resistance factors will undoubtedly accelerate, rendering this aminoglycoside increasingly obsolete. Understanding resistance to plazomicin is an important step to ensure this aminoglycoside remains a viable treatment option for the foreseeable future. Here, we present three crystal structures of AAC(2')-Ia from P. stuartii, two in complex with acetylated aminoglycosides tobramycin and netilmicin, and one in complex with a non-substrate aminoglycoside, amikacin. Together, with our previously reported AAC(2')-Ia-acetylated plazomicin complex, these structures outline AAC(2')-Ia's specificity for a wide range of aminoglycosides. Additionally, our survey of AAC(2')-I homologues highlights the conservation of residues predicted to be involved in aminoglycoside binding, and identifies the presence of plasmid-encoded enzymes in environmental strains that confer resistance to the latest next-generation aminoglycoside. These results forecast the likely spread of plazomicin resistance and highlight the urgency for advancements in next-generation aminoglycoside design.

Adverse Drug Reactions with First-Line and Second-Line Drugs in Treatment of Tuberculosis

Drug-susceptible tuberculosis (DS-TB) requires treatment with first-line drugs (FLDs) whereas drug-resistant TB (DR-TB) are treated with combination of second-line drugs (SLDs) and fewer FLDs. Adverse drug reactions (ADRs) to these drugs are quite evident as they are being used for longer duration. The overall prevalence of ADRs with FLDs and SLDs are estimated to vary from 8.0 to 85 and 69 to 96%, respectively. Most ADRs are observed in the intensive phase as compared to continuation phase. Major concerns exist regarding treatment of DR-TB patients, especially with SLDs having lower efficacy more toxicity and high cost as compared to FLDs. A variety of ADRs may be produced by anti-TB drugs ranging from mild or minor to severe or major like gastrointestinal toxicity (nausea/vomiting, diarrhoea, and hepatotoxicity), ototoxicity, neurotoxicity (peripheral neuropathy and seizures), nephrotoxicity, cutaneous toxicity, and cardiotoxicity. Most of ADRs are minor and can be managed without discontinuation of treatment. Few ADRs’ can be major causing life-threatening experience leading to either modification or discontinuation of regimen and even mortality. A careful monitoring of ADRs during the treatment with anti-TB drugs and early recognition and appropriate management of these ADRs might improve adherence leading to favorable outcome.

Investigation of treatment-time differences in colistin-induced nephrotoxicity in Wistar rats

Colistin-induced nephrotoxicity (CIN) occurs in up to 60% of patients, and this has restricted its clinical use. In view of its efficacy amidst the rising challenge of infections caused by multidrug-resistant bacteria, current studies are focusing on ways to ameliorate colistin-induced nephrotoxicity. This study investigated treatment-time differences in colistin-induced nephrotoxicity in Wistar rats. A dose of 600,000 IU/Kg/day of colistimethate sodium (CMS) was administered to male Wistar rats to induce nephrotoxicity; the rats tolerated the higher dose for the treatment duration with higher mean values of serum creatinine, urea, and malondialdehyde compared to the group that received 450,000 IU/Kg/day CMS (p ≤ 0.05). Four groups (n = 8/group) of rats received intraperitoneal (i.p.) injections of 600,000 IU/Kg/day CMS each at four equally spaced circadian times (00:00, 06:00, 12:00, and 18:00 h) to determine the time of administration with least renal toxicity. Biomarkers of oxidative stress and renal toxicity were measured and kidney histology studied after the treatments. The results showed a 24-h pattern in nephrotoxicity from CIN, and that treatment during the activity time period (dark phase) caused lowest CIN. Histological findings supported this finding, with photomicrographs consistently showing more pronounced features of CIN in the groups treated during time frame that coincided with the rest phase in rats (12:00 and 18:00).

A Review on Drug-Induced Nephrotoxicity: Pathophysiological Mechanisms, Drug Classes, Clinical Management, and Recent Advances in Mathematical Modeling and Simulation Approaches

A variety of marketed drugs belonging to various therapeutic classes are known to cause nephrotoxicity. Nephrotoxicity can manifest itself in several forms depending on the specific site involved as well as the underlying pathophysiological mechanisms. As they often coexist with other pathophysiological conditions, the steps that can be taken to treat them are often limited. Thus, drug-induced nephrotoxicity remains a major clinical challenge. Prior knowledge of risk factors associated with special patient populations and specific classes of drugs, combined with early diagnosis, therapeutic drug monitoring with dose adjustments, as well as timely prospective treatments are essential to prevent and manage them better. Most incident drug-induced renal toxicity is reversible only if diagnosed at an early stage and treated promptly. Hence, diagnosis at an early stage is the need of the hour to counter it. Significant recent advances in the identification of novel early biomarkers of nephrotoxicity are not beyond limitations. In such a scenario, mathematical modeling and simulation (M&S) approaches may help to better understand and predict toxicities in a clinical setting. This review summarizes pathophysiological mechanisms of drug-induced nephrotoxicity, classes of nephrotoxic drugs, management, prevention, and diagnosis in clinics. Finally, it also highlights some of the recent advancements in mathematical M&S approaches that could be used to better understand and predict drug-induced nephrotoxicity.

Adverse drug reactions in tuberculosis and management

BACKGROUND

Treatment of drug susceptible tuberculosis (DS-TB) requires regimens containing first line drugs (FLDs') whereas drug resistant tuberculosis (DR-TB) are treated with regimens comprising combination of both second line drugs (SLDs') and few FLDs'. Adverse drug reactions (ADRs') to these anti-tubercular drugs are quite common as they are being used for longer duration. ADRs' may cause associated morbidity and even mortality if not recognized early. There are major concerns regarding treatment of DR-TB patients particularly with SLDs' in that they are expensive, have low efficacy and more toxic as compared to FLDs'. There may be a severe impact on adherence and higher risk of default and treatment failure affecting outcome overall if such ADRs' are not properly managed.

METHODS

A search strategy was adopted involving principal electronic databases (Pubmed, EMBASE, Google and Google scholar) of English language articles from 1990 till now, using various terms in combination. All articles with resulting titles, abstract and full text, when available were read and kept for reference.

RESULTS

101 articles including 4 systematic reviews have been identified. The overall prevalence of ADRs' with FLDs' and SLDs' are estimated to vary from 8.0% to 85% and 69% to 96% respectively. Most ADRs' are observed in the intensive phase as compared to continuation phase. No difference in frequency of ADRs' was reported with intermittent or daily intake of anti-tubercular drugs. The occurrence of ADRs' may be influenced by multiple factors and may range from mild gastrointestinal disturbances to serious hepatotoxicity, ototoxicity, nephrotoxicity peripheral neuropathy, cutaneous ADRs', etc. Most of ADRs' are minor and can be managed without discontinuation of treatment. Some ADRs' can be major or severe causing life-threatening experience leading to either modification or discontinuation of regimen and even mortality if not recognized and treated promptly.

CONCLUSION

Early recognition by active surveillance and appropriate management of these ADRs' might improve adherence and treatment success.

Population pharmacokinetic modelling, Monte Carlo simulation and semi-mechanistic pharmacodynamic modelling as tools to personalize gentamicin therapy

Population pharmacokinetic modelling, Monte Carlo simulation and semi-mechanistic pharmacodynamic modelling are all tools that can be applied to personalize gentamicin therapy. This review summarizes and evaluates literature knowledge on the population pharmacokinetics and pharmacodynamics of gentamicin and identifies areas where further research is required to successfully individualize gentamicin therapy using modelling and simulation techniques. Thirty-five studies have developed a population pharmacokinetic model of gentamicin and 15 studies have made dosing recommendations based on Monte Carlo simulation. Variability in gentamicin clearance was most commonly related to renal function in adults and body weight and age in paediatrics. Nine studies have related aminoglycoside exposure indices to clinical outcomes. Most commonly, efficacy has been linked to a Cmax/MIC ≥7-10 and a AUC24/MIC ≥70-100. No study to date has shown a relationship between predicted achievement of exposure targets and actual clinical success. Five studies have developed a semi-mechanistic pharmacokinetic/pharmacodynamic model to predict bacteria killing and regrowth following gentamicin exposure and one study has developed a deterministic model of aminoglycoside nephrotoxicity. More complex semi-mechanistic models are required that consider the immune response, use of multiple antibiotics, the severity of illness, and both efficacy and toxicity. As our understanding grows, dosing of gentamicin based on sound pharmacokinetic/pharmacodynamic principles should be applied more commonly in clinical practice.

Modelling Drug Abuse Epidemics in the Presence of Limited Rehabilitation Capacity

The abuse of drugs is now an epidemic globally whose control has been mainly through rehabilitation. The demand for drug abuse rehabilitation has not been matched with the available capacity resulting in limited placement of addicts into rehabilitation. In this paper, we model limited rehabilitation through the Hill function incorporated into a system of nonlinear ordinary differential equations. Not every member of the community is equally likely to embark on drug use, risk structure is included to help differentiate those more likely (high risk) to abuse drugs and those less likely (low risk) to abuse drugs. It is shown that the model has multiple equilibria, and using the centre manifold theory, the model exhibits the phenomenon of backward bifurcation whose implications to rehabilitation are discussed. Sensitivity analysis and numerical simulations are performed. The results show that saturation in rehabilitation will in the long run lead to the escalation of drug abuse. This means that limited access to rehabilitation has negative implications in the fight against drug abuse where rehabilitation is the main form of control. This suggests that increased access to rehabilitation is likely to lower the drug abuse epidemic.

Urinary kidney injury biomarkers and tobramycin clearance among children and young adults with cystic fibrosis: a population pharmacokinetic analysis

BACKGROUND

Tobramycin is frequently used for treatment of bronchopneumonia in patients with cystic fibrosis (CF). Variability in tobramycin clearance (CL) is high in this population with few reliable approaches to guide dosing.

OBJECTIVES

We sought to evaluate the pharmacokinetics of once-daily intravenous tobramycin in patients with CF and test the influence of covariates on tobramycin CL, including serum creatinine (SCr) and urinary biomarkers: neutrophil gelatinase-associated lipocalin (NGAL), retinol-binding protein (RBP) and kidney injury molecule-1 (KIM-1).

METHODS

This was a prospective, observational cohort study of children/young adults with CF receiving once-daily intravenous tobramycin from October 2012 to May 2014 at Cincinnati Children's Hospital Medical Center. Therapeutic drug monitoring data were prospectively obtained. Population pharmacokinetic analyses were performed using non-linear mixed-effects modelling.

RESULTS

Thirty-seven patients (median age 15.3 years, IQR 12.7-19.5) received 62 tobramycin courses. A one-compartment model with allometrically scaled weight for tobramycin CL and volume of distribution (V) best described the data. Urinary NGAL was associated with tobramycin CL (P < 0.001), as was urinary RBP (P < 0.001). SCr, estimated glomerular filtration rate and urinary KIM-1 were not significant covariates. The population pharmacokinetic parameter estimates were CL = 8.60 L/h/70 kg (relative standard error 4.3%) and V = 31.3 L/70 kg (relative standard error 4.7%).

CONCLUSIONS

We describe urinary biomarkers as predictors of tobramycin CL using a population pharmacokinetic modelling approach. Our findings suggest that patient weight and urinary NGAL or RBP could be used to individualize tobramycin therapy in patients with CF.

Fit-for-purpose chromatographic method for the determination of amikacin in human plasma for the dosage control of patients

In this paper, a simple, rapid and sensitive method based on liquid chromatography with fluorimetric detection (HPLC-FLD) for the determination of amikacin (AMK) in human plasma is developed. Determination is performed by pre-column derivatization of AMK with ortho-phtalaldehyde (OPA) in presence of N-acetyl-L-cysteine (NAC) at pH 9.5 for 5 min at 80 °C. In our knowledge, this is the first time that NAC has been used in AMK derivatization. Derivatization conditions (pH, AMK/OPA/NAC molar ratios, temperature and reaction time) are optimized to obtain a single and stable, at room temperature, derivative. Separation of the derivative is achieved on a reversed phase LC column (Kromasil C18, 5 μm, 150 × 4.6 i.d. mm) with a mobile phase of 0.05 M phosphate buffer:acetonitrile (80:20, v/v) pumped at flow rate of 1.0 mL/min. Detection is performed using 337 and 439 nm for excitation and emission wavelengths, respectively. The method is fitted for the purpose of being a competitive alternative to the currently used method in many hospitals for AMK dosage control: fluorescence polarization immunoassay (FPIA). The method exhibits linearity in the 0.17-10 µg mL(-1) concentration range with a squared correlation coefficient higher than 0.995. Trueness and intermediate precision are estimated using spiked drug free plasma samples, which fulfill current UNE-EN ISO15189:2007 accreditation schemes. Finally, for the first time, statistical comparison against the FPIA method is demonstrated using plasma samples from 31 patients under treatment with AMK.

Neamine and 2-deoxystreptamine neomycin derivatives exhibit antinociceptive activity in rat models of phasic, incision and neuropathic pain

OBJECTIVES

To assess the antinociceptive activity of the neomycin derivatives neamine and 2-deoxystreptamine following intraspinal administration in rats.

METHODS

We used the tail-flick test and measured the threshold to mechanical stimulation in models of incisional and neuropathic pain.

KEY FINDINGS

The derivatives produced antinociception in the tail-flick test and reduced mechanical allodynia in models of incisional and neuropathic pain. The approximate ED50 in milligrams (confidence limits in parenthesis) in these tests were 1.35 mg (0.61; 2.95), 0.20 mg (0.14; 0.27) and 0.28 mg (0.12; 0.63) for neamine, and 1.05 mg (0.68; 1.60), 0.78 mg (0.776; 0.783) and 0.79 mg (0.46; 1.34) for 2-deoxystreptamine, respectively. Neamine was more potent than 2-deoxystreptamine in the incisional and neuropathic pain models, but they had similar potency in the tail-flick test. Tetra-azidoneamine, a neamine derivative in which free amino groups are replaced with azido groups, did not change the incisional mechanical allodynia. The reduction of incisional allodynia by neamine and 2-deoxystreptamine was transitorily antagonized by intrathecal administration of calcium chloride.

CONCLUSIONS

The intraspinal administration of neamine and 2-deoxystreptamine is antinociceptive in rats. The presence of amino groups in the structure of these derivatives is fundamental to their antinociceptive effect, which may be due to a calcium antagonist activity.

Arbekacin: another novel agent for treating infections due to methicillin-resistant Staphylococcus aureus and multidrug-resistant Gram-negative pathogens

Arbekacin sulfate (ABK), an aminoglycoside antibiotic, was discovered in 1972 and was derived from dibekacin to stabilize many common aminoglycoside modifying enzymes. ABK shows broad antimicrobial activities against not only Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) but also Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. ABK has been approved as an injectable formulation in Japan since 1990, under the trade name Habekacin, for the treatment of patients with pneumonia and sepsis caused by MRSA. The drug has been used in more than 250,000 patients, and its clinical benefit and safety have been proven over two decades. ABK currently shows promise for the application for the treatment of multidrug-resistant Gram-negative bacterial infections such as multidrug-resistant strains of P. aeruginosa and Acinetobacter baumannii because of its synergistic effect in combination with beta-lactams.

Pharmacokinetic-pharmacodynamic modeling of antibacterial drugs

Pharmacokinetic-pharmacodynamic (PKPD) modeling and simulation has evolved as an important tool for rational drug development and drug use, where developed models characterize both the typical trends in the data and quantify the variability in relationships between dose, concentration, and desired effects and side effects. In parallel, rapid emergence of antibiotic-resistant bacteria imposes new challenges on modern health care. Models that can characterize bacterial growth, bacterial killing by antibiotics and immune system, and selection of resistance can provide valuable information on the interactions between antibiotics, bacteria, and host. Simulations from developed models allow for outcome predictions of untested scenarios, improved study designs, and optimized dosing regimens. Today, much quantitative information on antibiotic PKPD is thrown away by summarizing data into variables with limited possibilities for extrapolation to different dosing regimens and study populations. In vitro studies allow for flexible study designs and valuable information on time courses of antibiotic drug action. Such experiments have formed the basis for development of a variety of PKPD models that primarily differ in how antibiotic drug exposure induces amplification of resistant bacteria. The models have shown promise for efficacy predictions in patients, but few PKPD models describe time courses of antibiotic drug effects in animals and patients. We promote more extensive use of modeling and simulation to speed up development of new antibiotics and promising antibiotic drug combinations. This review summarizes the value of PKPD modeling and provides an overview of the characteristics of available PKPD models of antibiotics based on in vitro, animal, and patient data.

Guidelines for aminoglycoside use and applicability to geriatric patients

OBJECTIVES

The authors had for objective to evaluate the applicability of AFSSAPS guidelines for aminoglycoside use to geriatric patients.

METHODS

Theoretical doses and dosing regimens allowing reaching target concentrations in this population were calculated by applying a pharmacokinetic model to 30 geriatric patients treated by amikacin.

RESULTS

The dose allowing reaching a maximum concentration of 60 mg/L was 1.217 mg on average. The time required to reach a blood concentration lower than or equal to 2.5mg/L was 62.5±70.4 hours. Forty-six percent of patients had a trough concentration greater than 2.5 mg/L, 48 hours after administration. For these patients, the time between critical minimum inhibitory concentration (MIC) and toxicity threshold concentration was 21.9±14.9 hours.

CONCLUSION

Reaching a target concentration can be problematic in geriatric patients. It is frequently necessary to use dosing intervals greater than 48 hours. The effectiveness and safety of these regimens remain uncertain.

Renoprotective effects of the crude extract and solvent fractions of the leaves of Euclea divinorum Hierns against gentamicin-induced nephrotoxicity in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Euclea divinorum Hierns (Ebenaceae) is used in Ethiopian folklore medicine to treat scabies, inflammation of the skin, eczema, abdominal pain, gonorrhea, and kidney problems. However, the claim has not been scientifically validated.

AIM OF THE STUDY

To assess the renoprotective effects of the crude extract and solvent fractions of E. divinorum leaves against gentamicin-induced nephrotoxicity in rats.

MATERIALS AND METHOD

Rats of either sex were divided into seven experimental groups, each comprising six animals. Group I served as control and given vehicle (Tween 80, 2%, v/v in water) and Group II were treated with gentamicin intraperitoneally (100mg/kg/day) for eight days. Group III-V received crude extract at three different doses 100mg/kg, 150mg/kg and 200mg/kg, respectively. Group VI received 100mg/kg of the methanolic fraction and Group VII 100mg/kg of the aqueous fraction. The extract was administered orally two days before and eight days concomitantly with gentamicin. Following treatment, blood and renal tissue were used to assess creatinine, blood urea nitrogen (BUN), malondialdehyde (MDA), antioxidant enzymes and tubular necrosis using recommended procedures. In addition, free radical scavenging activity was determined using in vitro methods.

RESULTS

Gentamicin significantly increased serum creatinine and BUN, MDA and tubular necrosis in rats. It also decreased activity of catalase and superoxide dismutase as well as levels of gluthatione. Pre- and co-treatment with the crude extract and solvent fractions of Euclea divinorum leaves reversed gentamicin-induced alterations as evidenced by a decrease in tubular necrosis, serum and oxidant markers as well as by an increase in antioxidant molecules. Effect was found to decrease with dose when the crude extract was used and maximum protection was conferred by 100mg/kg of the methanolic fraction in both in vivo and in vitro studies.

CONCLUSIONS

Euclea divinorum reversed gentamicin-induced nephrotoxicity, probably via its antioxidant activity. The fact that the methanol fraction conferred maximum protection suggests that semi-polar antioxidant principles might be responsible for the observed effect.

Diagnosis, evaluation, and management of acute kidney injury: a KDIGO summary (Part 1)

Acute kidney injury (AKI) is a common and serious problem affecting millions and causing death and disability for many. In 2012, Kidney Disease: Improving Global Outcomes completed the first ever, international, multidisciplinary, clinical practice guideline for AKI. The guideline is based on evidence review and appraisal, and covers AKI definition, risk assessment, evaluation, prevention, and treatment. In this review we summarize key aspects of the guideline including definition and staging of AKI, as well as evaluation and nondialytic management. Contrast-induced AKI and management of renal replacement therapy will be addressed in a separate review. Treatment recommendations are based on systematic reviews of relevant trials. Appraisal of the quality of the evidence and the strength of recommendations followed the Grading of Recommendations Assessment, Development and Evaluation approach. Limitations of the evidence are discussed and a detailed rationale for each recommendation is provided.

Novel in vitro and mathematical models for the prediction of chemical toxicity

The focus of much scientific and medical research is directed towards understanding the disease process and defining therapeutic intervention strategies. The scientific basis of drug safety is very complex and currently remains poorly understood, despite the fact that adverse drug reactions (ADRs) are a major health concern and a serious impediment to development of new medicines. Toxicity issues account for ∼21% drug attrition during drug development and safety testing strategies require considerable animal use. Mechanistic relationships between drug plasma levels and molecular/cellular events that culminate in whole organ toxicity underpins development of novel safety assessment strategies. Current in vitro test systems are poorly predictive of toxicity of chemicals entering the systemic circulation, particularly to the liver. Such systems fall short because of (1) the physiological gap between cells currently used and human hepatocytes existing in their native state, (2) the lack of physiological integration with other cells/systems within organs, required to amplify the initial toxicological lesion into overt toxicity, (3) the inability to assess how low level cell damage induced by chemicals may develop into overt organ toxicity in a minority of patients, (4) lack of consideration of systemic effects. Reproduction of centrilobular and periportal hepatocyte phenotypes in in vitro culture is crucial for sensitive detection of cellular stress. Hepatocyte metabolism/phenotype is dependent on cell position along the liver lobule, with corresponding differences in exposure to substrate, oxygen and hormone gradients. Application of bioartificial liver (BAL) technology can encompass in vitro predictive toxicity testing with enhanced sensitivity and improved mechanistic understanding. Combining this technology with mechanistic mathematical models describing intracellular metabolism, fluid-flow, substrate, hormone and nutrient distribution provides the opportunity to design the BAL specifically to mimic the in vivo scenario. Such mathematical models enable theoretical hypothesis testing, will inform the design of in vitro experiments, and will enable both refinement and reduction of in vivo animal trials. In this way, development of novel mathematical modelling tools will help to focus and direct in vitro and in vivo research, and can be used as a framework for other areas of drug safety science.

Impact of combination therapy with aminoglycosides on the outcome of ICU-acquired bacteraemias

Pharmacodynamic studies report on the rapid bactericidal activity of aminoglycosides, conferring them as being of theoretical interest for bacteraemia treatment. We assessed this issue in a retrospective study of patients with intensive care unit (ICU)-acquired bacteraemias. To determine the impact of aminoglycosides in antimicrobial combination on the outcome of patients with bacteraemia, we performed a monovariate analysis and a logistic regression analysis comparing patients treated with or without aminoglycosides. Forty-eight bacteraemias in 48 patients were included. Eighteen patients received aminoglycosides. Baseline characteristics as well as adaptation and adequation of antibiotherapy did not differ in patients who did or did not receive aminoglycosides. Patients who received aminoglycosides had longer time alive away from the ICU (11.3 ± 8.9 (10 [0–20]) vs. 3.2 ± 6.6 (0 [0–2] days; p = 0.002) and free from mechanical ventilation (12.5 ± 9.3 (14 [0–21] vs. 5.5 ± 9.2 (0 [0–10] days; p = 0.02) on day 28. The ICU mortality was 16% in the aminoglycoside group versus 46% (p = 0.03). In the multivariate analysis, patients treated with aminoglycosides were 6 times less likely to die than those treated without aminoglycosides (confidence interval [CI] = [1.3–28.9]; p = 0.02). Our study supports the hypothesis that combination short-term antibiotherapy with an aminoglycoside for ICU-acquired bacteraemias could increase survival.

Ototoxic destruction by co-administration of kanamycin and ethacrynic acid in rats

It is well known that ethacrynic acid (EA) can potentiate the ototoxicity of aminoglycoside antibiotics (AmAn) such as kanamycin (KM), if they were applied at the same time. Currently, to create the model of EA-KM-induced cochlear lesion in rats, adult rats received a single injection of EA (75 mg/kg, intravenous injection), or followed immediately by KM (500 mg/kg, intramuscular injection). The hearing function was assessed by auditory brainstem response (ABR) measurement in response to click and/or tone bursts at 4, 8, 12, 16, 20, 24, and 32 kHz. The static microcirculation status in the stria vascularis after a single EA injection was evaluated with eosin staining. The pathological changes in cochlear and vestibular hair cells were also quantified after co-administration of EA and KM. After a single EA injection, blood flow in vessels supplying the stria vascularis rapidly diminished. However, the blood supply to the cochlear lateral wall partially recovered 5 h after EA treatment. Threshold changes in ABR were basically parallel to the microcirculation changes in stria vascularis after single EA treatment. Importantly, disposable co-administration of EA and KM resulted in a permanent hearing loss and severe damage to the cochlear hair cells, but spared the vestibular hair cells. Since the cochlear lateral wall is the important part of the blood-cochlea barrier, EA-induced anoxic damage to the epithelium of stria vascularis may enhance the entry of KM to the cochlea. Thus, experimental animal model of selective cochlear damage with normal vestibular systems can be reliably created through co-administration of EA and KM.

Antituberculosis drugs: drug interactions, adverse effects, and use in special situations. Part 2: second line drugs

The main objectives of tuberculosis therapy are to cure the patients and to minimize the possibility of transmission of the bacillus to healthy subjects. Adverse effects of antituberculosis drugs or drug interactions (among antituberculosis drugs or between antituberculosis drugs and other drugs) can make it necessary to modify or discontinue treatment. We describe the general mechanism of action, absorption, metabolization, and excretion of the drugs used to treat multidrug resistant tuberculosis (aminoglycosides, fluoroquinolones, cycloserine/terizidone, ethionamide, capreomycin, and para-aminosalicylic acid). We describe adverse drug reactions and interactions (with other drugs, food, and antacids), as well as the most appropriate approach to special situations, such as pregnancy, breastfeeding, liver failure, and kidney failure.

Acute renal failure after topical fortified gentamicin and vancomycin eyedrops

PURPOSE

To report a case of acute renal failure after topical fortified gentamicin and vancomycin eyedrops in the treatment of endophthalmitis.

METHODS

A 67-year-old lady with diabetes mellitus was treated for bleb-related endophthalmitis. After intravitreal antibiotics, she was given oral ciprofloxacin, fortified gentamicin, and vancomycin eyedrops. She developed acute renal failure a few days after therapy. Blood tests and ultrasound of the urinary system were performed to investigate for the cause of the renal failure.

RESULTS

No apparent cause of renal failure could be identified in our patient. Autoimmune markers and ultrasound of the urinary system were unremarkable. Fortified gentamicin and vancomycin eyedrops were stopped on day 9 and 13, respectively. The renal function recovered dramatically. The gentamicin level was checked 2 days after it had been stopped, and the serum level was 0.34 mg/L. Renal function improved on supportive management without dialysis. Serum creatinine level completely normalized 2 months later.

CONCLUSIONS

This is the first article that demonstrated a detectable level of serum gentamicin level after usage of topical eyedrops. This is also the first article demonstrating that nephrotoxicity of topical fortified gentamicin and vancomycin eyedrops was found. The acute renal failure in our patient recovered completely after cessation of the eyedrops.

Patient variation in veterinary medicine--part II--influence of physiological variables

In veterinary medicine, the characterization of a drug's pharmacokinetic properties is generally based upon data that are derived from studies that employ small groups of young healthy animals, often of a single breed. In Part I of the series, we focused on the potential influence of disease processes, stress, pregnancy and lactation on drug pharmacokinetics. In this Part II of the series, we consider other covariates, such as gender, heritable traits, age, body composition, and circadian rhythms. The impact of these factors with respect to predicting the relationship between dose and drug exposure characteristics within an animal population is illustrated through the use of Monte Carlo simulations. Ultimately, an appreciation of these potential influences will improve the prediction of situations when dose adjustments may be appropriate.

[Biological rhythms for anaesthesia and intensive care]

Knowledge of biological rhythms has led to better understanding of the time-of-day dependent effects of anaesthetic drugs. These chronopharmacological effects are currently explained by the biological rhythms modulating the pharmacokinetic, toxic and pharmacodynamic parameters of these substances. Such effect has been described for general anesthetics, local anaesthetics, analgesics as well as for antibiotics. But recent data also highlight that general anaesthetics, probably part of their brain effects, also alter the regulation of biological rhythms, including the sleep-wake or the endogenous circadian temperature rhythms. This desynchronization of biological rhythms can led to disturbance of the circadian secretion of many substances, including hormones. Finally, biological rhythms have been also described with regard to physiology of pain and cardiovascular physiopathology. The concept of biological rhythm should be present in mind not only for the clinical management of patients but also for setting studies in the field of anaesthesia, pain and intensive care.

Pharmacokinetics/pharmacodynamics of antibacterials in the Intensive Care Unit: setting appropriate dosing regimens

Patients admitted to Intensive Care Units (ICUs) are at very high risk of developing severe nosocomial infections. Consequently, antimicrobials are among the most important and commonly prescribed drugs in the management of these patients. Critically ill patients in ICUs include representatives of all age groups with a range of organ dysfunction related to severe acute illness that may complicate long-term illness. The range of organ dysfunction, together with drug interactions and other therapeutic interventions (e.g. haemodynamically active drugs and continuous renal replacement therapies), may strongly impact on antimicrobial pharmacokinetics in critically ill patients. In the last decade, it has become apparent that the intrinsic pharmacokinetic (PK) and pharmacodynamic (PD) properties are the major determinants of in vivo efficacy of antimicrobial agents. PK/PD parameters are essential in facilitating the translation of microbiological activity into clinical situations, ensuring a successful outcome. In this review, we analyse the typical patterns of antimicrobial activity and the corresponding PK/PD parameters, with a special focus on a PK/PD dosing approach of the antimicrobial agent classes commonly utilised in the ICU setting.

Comparative minimal inhibitory and mutant prevention drug concentrations of four fluoroquinolones against ocular isolates of Haemophilus influenzae

PURPOSE

Haemophilus influenzae is a known ocular pathogen, particularly in the pediatric population. The purpose of this study was to determine the minimal inhibitory concentration (MIC) and mutant prevention concentration (MPC) values of third-generation (i.e., ciprofloxacin and ofloxacin) and fourth-generation (i.e., gatifloxacin and moxifloxacin) fluoroquinolone antibiotics against clinical ocular isolates of H. influenzae.

METHODS

Twenty-six clinical isolates of H. influenzae were evaluated. For MIC testing, approximately 10(5) colony-forming units/mL of test organism was added to an H. influenzae test medium containing twofold dilution increments of each fluoroquinolone. Cultures were incubated for 18 to 24 hours at 35 degrees C to 37 degrees C in 5% CO2. The lowest drug concentration that prevented growth was recorded as the MIC. The lowest drug concentration that inhibited 90% of strains tested was recorded as the MIC90. To determine MPC values, more than 10(10) bacteria were inoculated to agar plates containing varying drug concentrations and incubated for 24 to 48 hours at 35 degrees C to 37 degrees C in 5% CO2. To confirm MPC values, bacteria isolated from drug-containing plates were subcultured to drug-free agar, incubated, and then subcultured to a plate with the same drug concentration. The lowest drug concentration that allowed no growth was recorded as the MPC.

RESULTS

All tested fluoroquinolones were highly active against H. influenzae. The MIC90 values were 0.016 microg/mL for gatifloxacin and ciprofloxacin and 0.031 microg/mL for moxifloxacin and ofloxacin. The MPC90 values were 0.125 microg/mL for gatifloxacin and 0.5 microg/mL for moxifloxacin, ofloxacin, and ciprofloxacin.

CONCLUSIONS

All evaluated fluoroquinolones were effective against H. influenzae. The MIC90 and MPC90 values for gatifloxacin were consistently lower than those for moxifloxacin.

Population pharmacokinetics of tobramycin administered thrice daily and once daily in children and adults with cystic fibrosis

BACKGROUND

Tobramycin pharmacokinetics have not been evaluated previously in a large series of data collected in children and adults with CF receiving once (OD) or three times daily (TD) tobramycin.

METHODS

Therapeutic drug monitoring data in children and adults with CF who participated in a randomised clinical trial evaluating efficacy and toxicity of OD versus TD tobramycin (TOPIC study) were analysed retrospectively. Population pharmacokinetic models stratified to treatment schedule were created, and individual pharmacokinetic parameters were calculated.

RESULTS

In paediatric patients, volume of distribution per kg body weight (V1) was greater with OD treatment compared to TD (0.401+/-0.092 versus 0.354+/-0.041, p=0.003). Elimination rate was reduced in all patients receiving OD tobramycin compared to TD (children: 0.00197+/-0.00027 versus 0.00291+/-0.00041, p<0.001, adults: 0.00252+/-0.00008 versus 0.00322+/-0.00050, p<0.001). Tobramycin V1 decreased with increasing age (R(2)=0.3, p<0.001).

CONCLUSIONS

The reduced elimination rate in OD may either be caused by circadian pharmacokinetic behaviour of tobramycin or indicates early renal damage caused by high tobramycin doses not detected by biochemical measurements. However, results of our previous work suggest that OD tobramycin may be less nephrotoxic. The higher V1 in children implies that a relative higher tobramycin dose in these patients is needed for the same target peak serum concentration.

Chronobiology and chronotoxicology of antibiotics and aminoglycosides

Few investigators have examined the circadian variation in the symptom intensity of infectious diseases. Seasonal patterns in a variety of infectious are well know. Less appreciated are the circadian patterns in the symptom expression of infections. Studies indicate that fever which accompanies the common cold peaks at 4 p.m., and this is in agreement with other studies indicating that the elevation of body temperature, fever, due to bacterial infections is higher in the evening while that due to viral infections is more likely in the morning. Animal and human studies reveal also administration-time-dependent differences in the pharmacokinetics and toxicity of antimicrobial agents. This is particularly true for the aminoglycosides, as their nephrotoxicity is greatest when administered during the resting period of laboratory animals and human beings. Food intake and low urinary pH has been found to be protective of the toxicity of aminoglycosides at this time of the day. Knowledge of the administration-time-dependence of aminoglycosides and the underlying mechanisms can be used to develop once-a-day formulations that are significantly less toxic, in particular to the kidney, in patients who require around-the-clock antimicrobial therapy.

Circadian rhythms: mechanisms and therapeutic implications

The mammalian circadian system is organized in a hierarchical manner in that a central pacemaker in the suprachiasmatic nucleus (SCN) of the brain's hypothalamus synchronizes cellular circadian oscillators in most peripheral body cells. Fasting-feeding cycles accompanying rest-activity rhythms are the major timing cues in the synchronization of many, if not most, peripheral clocks, suggesting that the temporal coordination of metabolism and proliferation is a major task of the mammalian timing system. The inactivation of noxious food components by hepatic, intestinal, and renal detoxification systems is among the metabolic processes regulated in a circadian manner, with the understanding of the involved clock output pathways emerging. The rhythmic control of xenobiotic detoxification provides the molecular basis for the dosing time-dependence of drug toxicities and efficacy. This knowledge can in turn be used in improving or designing chronotherapeutics for the patients who suffer from many of the major human diseases.

Lack of effect of DX-619, a novel des-fluoro(6)-quinolone, on glomerular filtration rate measured by serum clearance of cold iohexol

DX-619 is a novel des-fluoro(6)-quinolone with activity against a broad range of bacterial strains, including methicillin-resistant Staphylococcus aureus. The effects of DX-619 on the glomerular filtration rate (GFR) were evaluated because drug-related increases in serum creatinine levels were observed in studies with healthy volunteers. Forty-one healthy subjects were randomized to receive intravenous DX-619 at 800 mg or placebo once daily for 4 days, and the GFR was directly measured by determination of the clearance of a bolus iohexol injection in 33 subjects who completed the study per protocol. DX-619 was noninferior to placebo for the GFR on the basis of a criterion for a clinically significant difference of -12 ml/min/1.73 m(2). The mean GFRs on day 4 were 101.1 +/- 14.2 ml/min/1.73 m(2) and 100.2 +/- 15.6 ml/min/1.73 m(2) for the volunteers receiving placebo and DX-619, respectively. On day 4 the mean serum creatinine concentration for volunteers receiving DX-619 increased by 30 to 40%, with a corresponding decrease in mean creatinine clearance. Both parameters normalized within 7 days after the cessation of DX-619 treatment. Nonclinical studies suggest that DX-619 increases the serum creatinine concentration by inhibiting excretory tubular transporters. In conclusion, DX-619 administered intravenously at 800 mg once a day for 4 days did not affect the GFR in healthy volunteers. Glomerular toxicity is not expected to present a risk to patients receiving DX-619 in clinical trials, but monitoring of the renal function, with an emphasis on the serum creatinine concentration, is still warranted.