A prospective comparative study of gentamicin- and amikacin-induced nephrotoxicity in patients with normal baseline renal function

Appropriateness of gentamicin therapeutic drug monitoring at a Middle Eastern tertiary hospital setting: a retrospective evaluation and quality audit

Introduction

The use of gentamicin in the treatment of infectious diseases requires frequent monitoring to attain the best treatment outcomes.

Objective

This study aimed to evaluate the appropriateness of gentamicin therapeutic drug monitoring (TDM) at a tertiary care hospital in Qatar.

Methods

A one-year quantitative retrospective chart review of all gentamicin TDM records was conducted. Evidence-based criteria were applied to evaluate the appropriateness of gentamicin TDM in terms of indication, sampling times, and post-analytical actions.

Results

Out of 59 captured gentamicin TDM records, 58 gentamicin samples were eligible for evaluation. Overall, gentamicin TDM appropriateness was achieved in 50% (n = 29) of the evaluated records. However, 12% (n = 7) of gentamicin drug concentrations were below the assay quantification limits or were not sampled appropriately. Inappropriate post-analytical actions (22.4%, n = 13) and inappropriate sampling times (44.8%, n = 26) were recorded. Most of the gentamicin blood samples (n = 43; 74.2%) were taken appropriately at steady-state. Inappropriate sampling time relative to the last dose was captured in 31% (n = 18) of the cases. Although 27.6% (n = 16) of gentamicin concentrations were non-therapeutic, continuing gentamicin dosing without adjustment was the most frequent post-analytical action (69.8%, n = 37). Gentamicin dose regimen continuations, dose regimen decreases and dose regimen discontinuations were inappropriately applied in 27% (n = 10), 25% (n = 2) and 14% (n = 1) of the times, respectively.

Conclusion

Suboptimal gentamicin TDM practices exist in relation to sampling time and post-analytical actions. Studies exploring setting-specific reasons behind inappropriate TDM practices and methods of its optimisation are needed.

Linezolid: a safer and effective substitute to aminoglycoside in the treatment of actinomycetoma by Nocardia species

Actinomycetoma is chronic, suppurative, granulomatous infection caused by bacteria and requires prolonged antibiotic therapy preferrably in combinations. Nephrotoxicity is a common side effect of aminoglycosides used in the management of actinomycetoma. We report here two cases of actinomycetoma due to Nocardia species who received linezolid as a substitute to aminoglycosides after developing nephrotoxicity.

Prevention of nephrotoxicity induced by amikacin: The role of misoprostol, A prostaglandin E1 analogue

Amikacin (AK) is an aminoglycoside that is widely used to treat life-threatening Gram-negative infections, especially in intensive care units. Despite its wide clinical indications, AK causes serious side effects such as kidney toxicity. AK was found to lead to tissue damage primarily through apoptosis and oxidative stress. Therefore, it was investigated whether misoprostol (MP), which has antioxidant and antiapoptotic properties, had a beneficial effect on kidney damage caused by AK. It was observed that kidney injury molecule-1 (KIM-1) mRNA, blood urea nitrogen (BUN), creatinine (Cr), NADPH oxidase-4 (NOX-4) and Caspase-3 (CAS-3) levels increased in the AK-treated group in comparison with the control group, while uric acid, albumin, and total protein levels were decreased. In rats that were treated with AK+MP, the levels of KIM-1 mRNA, BUN, Cr, NOX-4 and CAS-3 were significantly decreased in comparison with the AK group, while uric acid, albumin and total protein levels increased. According to the obtained results, MP was found to be quite effective in the protection of kidneys from the toxic effects of AK.

Positive Bacterial Culture among Suspected Orthopedic Infections in a Tertiary Care Centre: A Descriptive Cross-sectional Study

Introduction

A hospital-based investigation of bacteriological isolates helps to identify common causative bacteria and their antibiotic sensitivity patterns. This helps in formulating presumptive antibiotic therapy and in reducing antibiotic misuse. The aim of this study was to find out the prevalence of positive bacterial culture isolates among suspected orthopaedic infections in a tertiary care centre.

Methods

A descriptive cross-sectional study was conducted from the electronic data record of the Department of Microbiology of a tertiary care centre from 1 January 2017 to 31 December 2021. The study was conducted following ethical approval from the Institutional Review Committee (Reference number: IRC-2021-11-09-1). Culture reports of suspected orthopaedic infections were evaluated, and those with missing data were excluded. A convenience sampling method was used. Point estimate and 95% Confidence Interval were calculated.

Results

Out of 6201 specimens, positive bacterial culture were found in 2957 (47.69%) (46.45-48.93, 95% Confidence Interval). Among them, 1561 (56.01%) were gram-negative organisms and 677 (24.29%) were gram-positive. A total of 2787 (94.25%) were wound/pus swab cultures and 170 (5.74%) were tissue cultures.

Conclusions

The prevalence of positive bacterial culture among suspected orthopaedic infections was lower than in other international studies. Among bacteriological isolates, gram-negative organisms are more than gram-positive organisms.

Keywords

culture techniques; infections; microbial sensitivity tests; prevalence.

Acute Kidney Injury and Renal Failure in Horses

Nephrotoxic and hemodynamically mediated disorders are the most common causes of acute renal failure (ARF) in horses and foals. Leptospira spp. is the most common infectious cause of ARF. Initial treatments for ARF include elimination of nephrotoxic drugs, correction of predisposing disorders, and fluid therapy to promote diuresis. Horses and foals with polyuric ARF often have a good prognosis, while those with oliguric or anuric ARF have a guarded to poor prognosis. When fluid therapy is unsuccessful in improving urine production, various drugs treatments have been used in an attempt to increase urine production, but none are consistently effective in converting oliguria to polyuria.

Hypothesis: How far are we from predicting multi-drug interactions during treatment for COVID-19 infection?

Seriously ill patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and hospitalized in intensive care units (ICUs) are commonly given a combination of drugs, a process known as multi-drug treatment. After extracting data on drug-drug interactions with clinical relevance from available online platforms, we hypothesize that an overall interaction map can be generated for all drugs administered. Furthermore, by combining this approach with simulations of cellular biochemical pathways, we may be able to explain the general clinical outcome. Finally, we postulate that by applying this strategy retrospectively to a cohort of patients hospitalized in ICU, a prediction of the timing of developing acute kidney injury (AKI) could be made. Whether or not this approach can be extended to other diseases is uncertain. Still, we believe it represents a valuable pharmacological insight to help improve clinical outcomes for severely ill patients.

Impact of Therapeutic Drug Monitoring on Once-Daily Regimen of Amikacin in Patients With Urinary Tract Infection: A Prospective Observational Study

BACKGROUND

Amikacin is a semisynthetic antibiotic used in the treatment of gram-negative bacterial infections and has a narrow therapeutic index. Although therapeutic drug monitoring is recommended for amikacin, it is not routinely performed because of the use of a less toxic once-daily regimen. Only few studies have evaluated the role of therapeutic drug monitoring in patients treated with amikacin. The objective of our study was to find an association between the pharmacokinetic parameters of amikacin and the time required for a clinical cure, creatinine clearance, and frequency of ototoxicity in patients with urinary tract infection treated for 7 or more days.

METHODS

A prospective study was conducted on patients with urinary tract infections who were administered amikacin for 7 or more days. Blood samples were obtained from the patients to measure the maximum drug concentration (Cmax) and trough concentration (Ctrough). Minimum inhibitory concentration (MIC) values were determined for patients with positive urine cultures. Serum creatinine levels were estimated every 3 days. The auditory assessment was performed using pure tone audiometry at baseline and weekly until the patients were discharged. Levels of amikacin were analyzed using a validated liquid chromatography-tandem mass spectrometry method.

RESULTS

Of 125 patients analyzed, the median time required for a clinical cure was less in the group of patients who achieved a Cmax/MIC ratio ≥8 than it was in those who did not achieve this level [7 versus 8 days (P = 0.02)]. The Ctrough of amikacin was associated with the change in serum creatinine level (P = 0.01) and the incidence of nephrotoxicity (P = 0.004).

CONCLUSIONS

In patients receiving short-term amikacin therapy, Cmax/MIC value can be used to predict the time required for a clinical cure. Ctrough can be used to predict the occurrence of nephrotoxicity in patients receiving amikacin therapy.

Unraveling the Gentamicin Drug Product Complexity Reveals Variation in Microbiological Activities and Nephrotoxicity

The gentamicin drug product is a complex mixture of numerous components, many of which have not individually undergone safety and efficacy assessments. This is in contrast to the majority of medicines that require rigorous characterizations of trace impurities and are dosed as single components. In gentamicin, four components, known as gentamicin congeners C1, C1a, C2, and C2a, comprise the majority of the mixture. A liquid chromatography-mass spectroscopy analysis revealed that the relative abundances of each gentamicin congener in commercial formulations can vary up to 1.9-fold depending on the commercial source of the gentamicin. To determine if the gentamicin used for antibiotic susceptibility testing (AST) would be predictive of the microbiological activity of the product used to dose patients, the relative abundances of the four congeners contained on commercial AST disks were measured. It was found that the congener abundances on the commercial AST disks varied up to 4.1-fold. After purification of the four gentamicin congeners, similar potencies against bacterial strains lacking aminoglycoside-modifying enzymes (AMEs) were observed. However, the potency of the congeners against strains harboring a common AME differed up to 128-fold. Nephrotoxicity of the individual gentamicin congeners also differed significantly in cell-based and repeat-dose rat nephrotoxicity studies. Variations in the composition of commercial gentamicin products combined with toxicity differences between gentamicin congeners suggest that some gentamicin formulations may be more nephrotoxic. Our results also raise the concern that gentamicin susceptibility test results may not be predictive of patient outcomes and could lead to unexpected clinical treatment failures.

Intravenously delivered aminoglycoside antibiotics, tobramycin and amikacin, are not ototoxic in mice

Many drugs on the World Health Organization's list of critical medicines are ototoxic, destroying sensory hair cells within the ear. These drugs preserve life, but patients can experience side effects including permanent hearing loss and vestibular dysfunction. Aminoglycoside ototoxicity was first recognised 80 years ago. However, no preventative treatments have been developed. In order to develop such treatments, we must identify the factors driving hair cell death. In vivo, studies of cell death are typically conducted using mouse models. However, a robust model of aminoglycoside ototoxicity does not exist. Previous studies testing aminoglycoside delivery via intraperitoneal or subcutaneous injection have produced variable ototoxic effects in the mouse. As a result, surgical drug delivery to the rodent ear is often used to achieve ototoxicity. However, this technique does not accurately model clinical practice. In the clinic, aminoglycosides are administered to humans intravenously (i.v.). However, repeated i.v. delivery has not been reported in the mouse. This study evaluated whether repeated i.v. administration of amikacin or tobramycin would induce hearing loss. Daily i.v. injections over a two-week period were well tolerated and transient low frequency hearing loss was observed in the aminoglycoside treatment groups. However, the hearing changes observed did not mimic the high frequency patterns of hearing loss observed in humans. Our results indicate that the i.v. delivery of tobramycin or amikacin is not an effective technique for inducing ototoxicity in mice. This result is consistent with previously published reports indicating that the mouse cochlea is resistant to systemically delivered aminoglycoside ototoxicity.

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

Background

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

Design

An observational, descriptive, cross-sectional study.

Setting

A 221-bed private hospital.

Participants

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

Interventions

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

Main outcomes measures

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

Results

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

Conclusions

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

Funding

None

Melatonin ameliorates the drug induced nephrotoxicity: Molecular insights

BACKGROUND

Drug-induced nephrotoxicity is a frequent adverse event that can lead to acute or chronic kidney disease and increase the healthcare expenditure. It has high morbidity and mortality incidence in 40-70% of renal injuries and accounts for 66% cases of renal failure in elderly population.

OBJECTIVE

Amelioration of drug-induced nephrotoxicity has been long soughed to improve the effectiveness of therapeutic drugs. This study was conducted to review the melatonin potential to prevent the pathogenesis of nephrotoxicity induced by important nephrotoxic drugs.

METHODS

We analyzed the relevant studies indexed in Pubmed, Medline, Scielo and Web of science to explain the molecular improvements following melatonin co-administration with special attention to oxidative stress, inflammation and apoptosis as key players of drug-induced nephrotoxicity.

RESULTS

A robust consensus among researchers of these studies suggested that melatonin efficiently eradicate the chain reaction of free radical production and induced the endogenous antioxidant enzymes which attenuate the lipid peroxidation of cellular membranes and subcellular oxidative stress in drug-induced nephrotoxicity. This agreement was further supported by the melatonin role in disintegration of inflammatory process through inhibition of principle pro-inflammatory or apoptotic cytokines such as TNF-α and NF-κB. These studies highlighted that alleviation of drug-induced renal toxicity is a function of melatonin potential to down regulate the cellular inflammatory and oxidative injury process and to stimulate the cellular repair or defensive mechanisms.

CONCLUSION

The comprehensive nephroprotection and safer profile suggests the melatonin to be a useful adjunct to improve the safety of nephrotoxic drugs.

Mesenchymal Stem Cell-based Therapy as a New Horizon for Kidney Injuries

Today, the prevalence of kidney diseases is increasing around the world, but there has still been no effective medical treatment. The therapeutic choices are confined to supportive cares and preventive strategies. Currently, mesenchymal stem cells (MSCs)-based cell therapy was proposed for the treatment of kidney injuries. However, after the transplantation of MSCs, they are exposed to masses of cytotoxic factors involving an inflammatory cytokine storm, a nutritionally-poor hypoxic environment and oxidative stresses that finally lead to minimize the efficacy of MSCs based cell therapy. Therefore, several innovative strategies were developed in order to potentiate MSCs to withstand the unfavorable microenvironments of the injured kidney tissues and improve their therapeutic potentials. This review aims to introduce MSCs as a new modality in the treatment of renal failure. Here, we discuss the clinical trials of MSCs-based therapy in kidney diseases as well as the in vivo studies dealing with MSCs application in kidney injuries mainly from the proliferation, differentiation, migration and survival points of view. The obstacles and challenges of this new modality in kidney injuries are also discussed.

Restrictive antibiotic stewardship associated with reduced hospital mortality in gram-negative infection

INTRODUCTION

: Antimicrobial stewardship has an important role in the control of Clostridium difficile infection (CDI) and antibiotic resistance. An important component of UK stewardship interventions is the restriction of broad-spectrum beta-lactam antibiotics and promotion of agents associated with a lower risk of CDI such as gentamicin. While the introduction of restrictive antibiotic guidance has been associated with improvements in CDI and antimicrobial resistance, evidence of the effect on outcome following severe infection is lacking.

METHODS

: In 2008, Glasgow hospitals introduced a restrictive antibiotic guideline. A retrospective before/after study assessed outcome following Gram-negative bacteraemia in the 2-year period around implementation.

RESULTS

: Introduction of restrictive antibiotic guidelines was associated with a reduction in utilization of ceftriaxone and co-amoxiclav and an increase in amoxicillin and gentamicin. Approximately 1593 episodes of bacteremia were included in the study. The mortality over 1-year following Gram-negative bacteraemia was lower in the period following guideline implementation (RR 0.852, P  = 0.045). There was no evidence of a difference in secondary outcomes including ITU admission, length of stay, readmission, recurrence of bacteraemia and need for renal replacement therapy. There was a fall in CDI (RR 0.571, P  = 0.014) and a reduction in bacterial resistance to ceftriaxone and co-amoxiclav but no evidence of an increase in gentamicin resistance after guideline implementation.

CONCLUSION

: Restrictive antibiotic guidelines were associated with a reduction in CDI and bacterial resistance but no evidence of adverse outcomes following Gram-negative bacteraemia. There was a small reduction in one year mortality.

The growing threat of multidrug-resistant Gram-negative infections in patients with hematologic malignancies

Prolonged neutropenia and chemotherapy-induced mucositis render patients with hematologic malignancies highly vulnerable to Gram-negative bacteremia. Unfortunately, multidrug-resistant (MDR) Gram-negative bacteria are increasingly encountered globally, and current guidelines for empirical antibiotic coverage in these patients may not adequately treat these bacteria. This expansion of resistance, coupled with traditional culturing techniques requiring 2-4 days for bacterial identification and antimicrobial susceptibility results, have grave implications for these immunocompromised hosts. This review characterizes the epidemiology, risk factors, resistance mechanisms, recommended treatments, and outcomes of the MDR Gram-negative bacteria that commonly cause infections in patients with hematologic malignancies. We also examine the infection prevention strategies in hematology patients, such as infection control practices, antimicrobial stewardship, and targeted decolonization. Finally, we assess the strategies to improve outcomes of the infected patients, including gastrointestinal screening to guide empirical antibiotic therapy, new rapid diagnostic tools for expeditious identification of MDR pathogens, and use of two new antimicrobial agents, ceftolozane/tazobactam and ceftazidime/avibactam.

Effects of 5-O-Ribosylation of Aminoglycosides on Antimicrobial Activity and Selective Perturbation of Bacterial Translation

We studied six pairs of aminoglycosides and their corresponding ribosylated derivatives synthesized by attaching a β-O-linked ribofuranose to the 5-OH of the deoxystreptamine ring of the parent pseudo-oligosaccharide antibiotic. Ribosylation of the 4,6-disubstituted 2-deoxystreptamine aminoglycoside kanamycin B led to improved selectivity for inhibition of prokaryotic relative to cytosolic eukaryotic in vitro translation. For the pseudodisaccharide aminoglycoside scaffolds neamine and nebramine, ribosylated derivatives were both more potent antimicrobials and more selective to inhibition of prokaryotic translation. On the basis of the results of this study, we suggest that modification of the 5-OH position of the streptamine ring of other natural or semisynthetic pseudodisaccharide aminoglycoside scaffolds containing an equatorial amine at the 2' sugar position with a β-O-linked ribofuranose is a promising avenue for the development of novel aminoglycoside antibiotics with improved efficacy and reduced toxicity.

The ameliorative effects of virgin olive oil and olive leaf extract on amikacin-induced nephrotoxicity in the rat

Amikacin is an important antibiotic, and its use is limited because of the induced nephrotoxicity. Thus, search for natural and synthetic agents that can moderate amikacin toxicity never stopped. The present study aims to investigate the possible ameliorative effects of virgin olive oil and olive leaf extract against the amikacin-induced nephrotoxicity in rat.

Methods

48 rats were distributed into 6 groups: 1-Animals of control (C) group were injected intraperitoneally (ip) with saline, 2-(AK); injected ip with amikacin {300 mg/kg/day for 12days}, 3-(OO) group: given olive oil {7 ml/kg/day for 16days}, 4-(OOAK) group: given olive oil as in OO and amikacin for 12days, 5-(OL) group: given olive leaf extract {50 mg/kg/day for 16days}, 6-(OLAK) group: given leaf extract as in OL and amikacin for 12days. Animals were fasted and sacrificed. Serum was used for biochemical analysis and kidneys for histopathology.

Results

Serum urea and creatinine were significantly (P < 0.001) elevated in AK, and significantly dropped in the OOAK and OLAK groups. Serum uric acid was reduced in AK by 45.29%. Kidneys from AK showed necrosis, whereas, those from OOAK and OLAK showed mild histology. The serum triglyceride was decreased by 17.8% in OL, by 37.02% in OOAK and by 31.48% in OLAK. The calculated amikacin effect showed a significant positive correlation with urea (r = 0.521, P = 0.0004), and a negative correlation with uric acid (r = ⿿ 0.58, P < 0.0001).

Conclusion

The study confirmed nephrotoxicity of amikacin in rat which was ameliorated by virgin olive oil and by olive leaf extract. Amikacin did not cause dyslipidemia but reduced serum uric acid.

Sensitization of intracellular Salmonella enterica serovar Typhimurium to aminoglycosides in vitro and in vivo by a host-targeted antimicrobial agent

Aminoglycosides exhibit relatively poor activity against intracellular Salmonella enterica serovar Typhimurium due to their low permeativity across eukaryotic cell membranes. Previously, we identified the unique ability of AR-12, a celecoxib-derived small-molecule agent, to eradicate intracellular Salmonella Typhimurium in macrophages by facilitating autophagosome formation and suppressing Akt kinase signaling. In light of this unique mode of antibacterial action, we investigated the ability of AR-12 to sensitize intracellular Salmonella to aminoglycosides in macrophages and in an animal model. The antibacterial activities of AR-12 combined with various aminoglycosides, including streptomycin, kanamycin, gentamicin, and amikacin, against intracellular S. Typhimurium in murine RAW264.7 macrophages were assessed. Cells were infected with S. Typhimurium followed by treatment with AR-12 or individual aminoglycosides or with combinations for 24 h. The in vivo efficacies of AR-12, alone or in combination with gentamicin or amikacin, were also assessed by treating S. Typhimurium-infected BALB/c mice daily for 14 consecutive days. Exposure of S. Typhimurium-infected RAW264.7 cells to a combination of AR-12 with individual aminoglycosides led to a reduction in bacterial survival (P < 0.05), both intracellular and extracellular, that was greater than that seen with the aminoglycosides alone. This sensitizing effect, however, was not associated with increased aminoglycoside penetration into bacteria or macrophages. Moreover, daily intraperitoneal injection of AR-12 at 0.1 mg/kg of body weight significantly increased the in vivo efficacy of gentamicin and amikacin in prolonging the survival of S. Typhimurium-infected mice. These findings indicate that the unique ability of AR-12 to enhance the in vivo efficacy of aminoglycosides might have translational potential for efforts to develop novel strategies for the treatment of salmonellosis.

Development of an automated imaging pipeline for the analysis of the zebrafish larval kidney

The analysis of kidney malformation caused by environmental influences during nephrogenesis or by hereditary nephropathies requires animal models allowing the in vivo observation of developmental processes. The zebrafish has emerged as a useful model system for the analysis of vertebrate organ development and function, and it is suitable for the identification of organotoxic or disease-modulating compounds on a larger scale. However, to fully exploit its potential in high content screening applications, dedicated protocols are required allowing the consistent visualization of inner organs such as the embryonic kidney. To this end, we developed a high content screening compatible pipeline for the automated imaging of standardized views of the developing pronephros in zebrafish larvae. Using a custom designed tool, cavities were generated in agarose coated microtiter plates allowing for accurate positioning and orientation of zebrafish larvae. This enabled the subsequent automated acquisition of stable and consistent dorsal views of pronephric kidneys. The established pipeline was applied in a pilot screen for the analysis of the impact of potentially nephrotoxic drugs on zebrafish pronephros development in the Tg(wt1b:EGFP) transgenic line in which the developing pronephros is highlighted by GFP expression. The consistent image data that was acquired allowed for quantification of gross morphological pronephric phenotypes, revealing concentration dependent effects of several compounds on nephrogenesis. In addition, applicability of the imaging pipeline was further confirmed in a morpholino based model for cilia-associated human genetic disorders associated with different intraflagellar transport genes. The developed tools and pipeline can be used to study various aspects in zebrafish kidney research, and can be readily adapted for the analysis of other organ systems.

Topographic and quantitative evaluation of gentamicin-induced damage to peripheral innervation of mouse cochleae

Ototoxicity induced by aminoglycoside antibiotics appears to occur both in hair cells (HCs) and the cochlear nerves that innervate them. Although HC loss can be easily quantified, neuronal lesions are difficult to quantify because two types of afferent dendrites and two types of efferent axons are tangled beneath the hair cells. In the present study, ototoxicity was induced by gentamicin in combination with the diuretic agent furosemide. Neuronal lesions were quantified in cochlear whole-mount preparations combined with microsections across the habenular perforate (HP) openings to achieve a clear picture of the topographic relationship between neuronal damage and HC loss. Multiple immunostaining methods were employed to differentiate the two types of afferent dendrites and two types of efferent axons. The results show that co-administration of gentamicin and furosemide resulted in a typical dynamic pattern of HC loss that spread from the basal turn to the outer hair cells to the apex and inner hair cells, depending on the dose and survival time after drug administration. Lesions of the innervation appeared to occur at two stages. At the early stage (2-4 days), the loss of labeling of the two types of afferent dendrites was more obvious than the loss of labeled efferent axons. At the late stage (2-4 weeks), the loss of labeled efferent axons was more rapid. In the high-dose gentamicin group, the loss of outer HCs was congruent with afferent dendrite loss at the early stage and efferent axon loss at the late stage. In the low-dose gentamicin group, the loss of labeling for cochlear innervation was more severe and widespread. Thus, we hypothesize that the gentamicin-induced damage to cochlear innervation occurs independently of hair cell loss.

Ascorbic acid reduces gentamicin-induced nephrotoxicity in rats through the control of reactive oxygen species

BACKGROUND & AIM

Oxidative stress has been implicated in the pathophysiology of many forms of acute renal failure. The aim was examine the effect of vitamin C on oxidative stress and its relationship with nitric oxide on gentamicin-induced nephrotoxicity in rats.

METHODS

We utilized 32 Wistar rats allocated in four groups of eight animals each: control (CTL), vitamin C (VIT C), gentamicin (GENTA), and GENTA + VIT C; all groups were treated during seven days.

RESULTS

Serum urea and creatinine, serum and renal tissue malondialdehyde, blood superoxide anion and hydrogen peroxide in GENTA were increased vs CTL and vs VIT C, and decreased in GENTA + VIT C vs GENTA (all P < 0.05). Serum nitric oxide increased in GENTA vs CTL and vs VIT C, and reduced in GENTA + VIT C vs GENTA (P < 0.001). Urinary nitric oxide was reduced in GENTA vs CTL and vs VIT C and increased in GENTA + VIT C vs GENTA (P < 0.001). Severe degeneration of proximal tubules was present in GENTA, but only mild lesions were observed in GENTA + VIT C.

CONCLUSION

This study suggests that VIT C is a valuable tool to protect against GENTA-induced nephrotoxicity, by reducing reactive oxygen species and increasing the nitric oxide.

Chronic kidney disease in Nicaragua: a qualitative analysis of semi-structured interviews with physicians and pharmacists

BACKGROUND

Northwestern Nicaragua has a high prevalence of chronic kidney disease (CKD) of unknown cause among young adult men. In addition, frequent occurrence of urinary tract infections (UTI) among men and a dysuria syndrome described by sugarcane workers as "chistata" are both reported. This study examines health professionals´ perceptions regarding etiology of these conditions and their treatment approaches, including use of potentially nephrotoxic medications.

METHODS

Nineteen in-person semi-structured interviews were conducted in November 2010 among ten physicians and nine pharmacists practicing in the region.

RESULTS

Health professionals perceived CKD as a serious and increasing problem in the region, primarily affecting young men working as manual laborers. All interviewees regarded occupational and environmental exposure to sun and heat, and dehydration as critical factors associated with the occurrence of CKD. These factors were also considered to play a role in the occurrence of chistata in the region. Health professionals indicated that reluctance among workers to hydrate might be influenced by perceptions of water contamination. Symptoms often were treated with non-steroidal anti-inflammatory drugs (NSAIDs), diuretics and antibiotics. Physicians acknowledged that the diagnosis of UTI usually was not based on microbial culture and opined that the use of potentially nephrotoxic medications may be contributing to CKD.

CONCLUSIONS

Interviews provided evidence suggesting that medications such as diuretics, antibiotics and NSAIDs are widely used and sold over the counter for symptoms that may be related to dehydration and volume depletion. These factors, alone or in combination, may be possible contributors to kidney damage. Acute kidney damage coupled with volume depletion and exposures including medications and infectious agents should be further evaluated as causal factors for CKD in this region.

Sulforaphane attenuates gentamicin-induced nephrotoxicity: role of mitochondrial protection

Sulforaphane (SFN), an isothiocyanate naturally occurring in Cruciferae, induces cytoprotection in several tissues. Its protective effect has been associated with its ability to induce cytoprotective enzymes through an Nrf2-dependent pathway. Gentamicin (GM) is a widely used antibiotic; nephrotoxicity is the main side effect of this compound. In this study, it was investigated if SFN is able to induce protection against GM-induced nephropathy both in renal epithelial LLC-PK1 cells in culture and in rats. SFN prevented GM-induced death and loss of mitochondrial membrane potential in LLC-PK1 cells. In addition, it attenuated GM-induced renal injury (proteinuria, increases in serum creatinine, in blood urea nitrogen, and in urinary excretion on N-acetyl-β-D-glucosaminidase, and decrease in creatinine clearance and in plasma glutathione peroxidase activity) and necrosis and apoptosis in rats. The apoptotic death was associated with enhanced active caspase-9. Caspase-8 was unchanged in all the studied groups. In addition, SFN was able to prevent GM-induced protein nitration and decrease in the activity of antioxidant enzymes catalase and glutathione peroxidase in renal cortex. In conclusion, the protective effect of SFN against GM-induced acute kidney injury could be associated with the preservation in mitochondrial function that would prevent the intrinsic apoptosis and nitrosative stress.

Caffeic acid phenethyl ester modulates gentamicin-induced oxidative nephrotoxicity in kidney of rats

In this study, the modulator effect of caffeic acid phenethyl ester (CAPE) on the oxidative nephrotoxicity of gentamicin in the kidneys of rats was investigated by determining indices of lipid peroxidation and the activities of antioxidant enzymes as well as by histological analyses. Forty female Wistar albino rats were randomly divided into four groups, namely control, gentamicin, CAPE, and gentamicin plus CAPE. On the 12th day of the study, all rats were sacrificed and then blood samples and kidneys were taken. Lipid peroxidation and nitric oxide levels, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) enzyme activities, and histological evaluation were measured in kidneys of rats. Levels of blood urea nitrogen and creatinine were studied in serum. CAPE with gentamicin caused decreases in lipid peroxidation, nitric oxide, urea nitrogen, and creatinine levels, although it caused increases in CAT, GSH-Px, and SOD activities when compared with gentamicin alone. In addition, on histological evaluation, the renal damage caused by gentamicin alone appeared much higher than that caused by CAPE plus gentamicin. It is concluded that oxidative stress plays a critical role in causing gentamicin nephrotoxicity and that this nephrotoxicity may be significantly reduced by CAPE.

The effect of grape seed proanthocyanidin extract in preventing amikacin-induced nephropathy

BACKGROUND/AIMS

Nephrotoxicity induced by aminoglycosides (AGs) limits their clinical use. As yet, no molecules have been approved to prevent AG nephropathy. We aim to investigate the effectiveness of grape seed proanthocyanidin extract (GSPE) in the prevention of amikacin (AK)-induced nephrotoxicity.

METHODS

A total of 24 rats were allocated into control, GSPE, AK, and AK + GSPE groups. While 1 mL saline was administered for 6 days in control and AK groups, 100 mg/kg GSPE was administered in GSPE and AK + GSPE groups. On day 7, intraperitoneal (i.p.) saline was administered in control and GSPE groups, while 1.2 g/kg i.p. AK was administered in AK and AK + GSPE groups. The experiment was terminated on day 9. Blood samples were taken for the measurement of renal functions. Renal tissues of the rats were removed for the analysis of malondialdehyde (MDA), total oxidant system (TOS), total antioxidant system, oxidative stress index (OSI), and for histopathological examination.

RESULTS

MDA level was found to be lower in GSPE group compared with other study groups. There was significantly more renal histopathological damage and higher blood urea nitrogen, creatinine, TOS, OSI, and MDA levels in the AK group compared with the control and AK + GSPE groups. The same parameters showed significant improvement in AK + GSPE group compared with AK group.

CONCLUSION

Our findings demonstrate for the first time that GSPE reduces oxidative damage in AK nephropathy and provides biochemical and renal histopathological improvements.

Tolerability and outcomes of kinetically guided therapy with gentamicin in critically ill neonates during the first week of life: an open-label, prospective study

BACKGROUND

Aminoglycosides are bactericidal antibiotics used worldwide for the treatment of serious infections in critically ill patients, including neonates. Critically ill neonates constitute a unique challenge in dosing owing to the pathologic alterations that accompany severe illness and the rapidly changing conditions of these patients.

OBJECTIVES

The main objective of this study was to analyze the kinetically guided dosage adjustment of gentamicin in neonates critically ill during the first week of life based on plasma concentrations after the first dose and to identify the impact of covariates (eg, fluid intake, body fluid retention) with respect to gestational age (GA). Tolerability of therapy was also assessed.

METHODS

This 10-day, open-label, prospective study included neonates critically ill during the first week of life admitted to the neonatal intensive care unit of a children's hospital between January 2006 and July 2009. Hearing and renal assessments were conducted over a 24-month follow-up period. The patients were treated with gentamicin for suspected sepsis, proven sepsis, or pneumonia as an early sign of sepsis. The first and second doses of gentamicin 4 mg/kg were adjusted according to birth weight and GA: group 1 (GA < 34 weeks), 48-hour interdose intervals; group 2 (GA 34-38 weeks), 36 hours; and group 3 (GA > 38 weeks), 24 or 48 hours. Individual pharmacokinetic parameters were estimated after the first dose (given in 30-minute intravenous infusions) using 4 concentrations. Individual pharmacokinetic parameters were estimated by fitting the parameters of a 2-compartment model into 4 concentrations. The last 2 blood samples were taken 30 minutes before the fourth infusion (C(trough,3)) and 1 hour after its start (C(max,4)). Dosing was individualized to reach target ranges for the C(trough,3) (0.5-2.0 mg/L) and C(max,4) (6-10 mg/L) values. If needed, initial dosing was changed after the second dose by adjusting (reducing or increasing) the third and subsequent doses, or by adjusting (prolonging or shortening) the interdose intervals. C(trough,3) and C(max,4) were assessed to determine differences between predicted and assayed values. Fluid retention was registered as the difference between fluid intake and urine output at different intervals related to the first dose per kilogram of birth weight, and from the start of the first infusion (0 hour) to the day of the fourth infusion. The C(max)/minimum inhibitory concentration (MIC) ratio was determined for assessment of optimal response. Tolerability was evaluated during the 24-month follow-up period using renal sonography to screen for nephrocalcinosis and transient evoked otoacoustic emission recordings to evaluate hearing abnormalities.

RESULTS

A total of 84 neonates (all white; 53 males, 31 females; birth weight range, 0.8-4.56 kg; GA range, 24-42 weeks) were enrolled in 3 groups: group 1, GA < 34 weeks, n = 27; group 2, GA 34-38 weeks, n = 22; and group 3, GA > 38 weeks, n = 35. The C(max) value detected 1 hour after the start of the first infusion (C(max,1)) reached the target range of 6-10 mg/L in 66 of the 84 neonates (79%). After the initial dose, C(max,1) was variable (%CV, 29%); the failure rate to reach 6 mg/L was 13%. V(d) decreased with GA (r = -0.30, P < 0.01) and achieved mean (SD) rates of 0.51 (0.10), 0.48 (0.13), and 0.40 (0.15) L/kg in groups 1, 2, and 3, respectively. Neither C(max) nor V(d) was correlated with fluid intake relative to the first infusion. Mean gentamicin clearance measured after dose 1 (0.47 [0.23], 0.66 [0.26], and 0.76 [0.32] mL/min/kg) increased with GA (r = 0.45, P < 0.001). The interdose interval was prolonged after the second and subsequent infusions in 8 of 84 neonates (10%) or by decreasing the third dose and subsequent doses in 51 neonates (61%). The target C(max,4) and C(trough,3) values occurred in 63% (22 of 35) and 83% (29 of 35) of full-term patients (GA >38 weeks), respectively. In preterm neonates, the target range for C(max,4) was reached in 11 of 27 patients (41%) in group 1 and 11 of 22 patients (50%) in group 2; for C(trough,3), the target range was reached in 25 patients (93%) in group 1 and in 16 (73%) in group 2. C(trough,3) >2 mg/L was detected in 1 full-term neonate, and gentamicin was withdrawn. Suspected fluid retention within the time period of 0 hour to the day of the fourth infusion was well correlated with actual body weight (r = 0.58, P < 0.001), but it was negatively correlated with C(max,4) (r = -0.25, P = 0.02). Thirteen of the 84 neonates (15%) had confirmed sepsis. C(max)/MIC was >12 except for 2 resistant staphylococcal infections (C(max)/MIC = 0.4); amikacin and vancomycin were substituted for gentamicin in these cases. Clinical signs and laboratory data indicative of suspected sepsis disappeared in 5 to 10 days in 68 of 71 neonates. In 1 neonate, gentamicin was withdrawn after dose 4 because of a high C(trough,3) value. In the 3 remaining neonates, C-reactive protein was decreased >10 days without changing therapy. Two neonates died, 1 of severe hypoxic-ischemic encephalopathy as a consequence of perinatal asphyxia and another of stage IV intraventricular hemorrhage. Transient renal dysfunction attributable to gentamicin was detected in 1 case. No signs of late toxicity (nephrocalcinosis) were found during the second year of follow-up. Two neonates were diagnosed with unilateral hearing loss, a secondary phenomenon of hypoxic-ischemic encephalopathy thought to be related to the severe perinatal asphyxia.

CONCLUSIONS

The initial dose of gentamicin 4 mg/kg for these critically ill premature and mature neonates with sepsis during the first week of life was high enough to reach bactericidal C(max,1) within 6-10 mg/L. C(max,1) <6 mg/L occurred in 13% of neonates. The interdose interval modified according to the recommendation resulted in C(trough) values within the target range of 0.5-2.0 mg/L in all but 2 neonates. The kinetically guided maintenance dosing of gentamicin based on plasma concentrations after the first dose should be optimized, taking into account actual body weight. (EudraCT number: 2005-002723-13).