Management of aminoglycosides in the intensive care unit

Reno-protective impact of diosmin and perindopril in amikacin-induced nephrotoxicity rat model: modulation of SIRT1/p53/C-FOS, NF-κB-p65, and keap-1/Nrf2/HO-1 signaling pathways

PURPOSE

Amikacin (AMC), an aminoglycoside antibiotic known for its rapid and potent bactericidal activity, is also associated with nephrotoxicity. Diosmin and perindopril have been reported to improve renal function and hold promise as therapeutic agents for preventing drug-induced nephrotoxicity. This study aimed to investigate the protective effect of Diosmin and perindopril, either alone or in combination, against renal damage induced by AMC toxicity and to elucidate the underlying mechanisms.

MATERIALS AND METHODS

The researchers evaluated the impact of Diosmin (50 mg/kg, orally) and perindopril (2 mg/kg, intraperitoneally) on AMC-induced kidney injury (1.2 g/kg, intraperitoneally) in rats. Invasive blood pressure, serum kidney function and toxicity parameters, oxidative stress biomarkers, and inflammatory cytokine levels in serum and renal tissue were assessed. Histopathological changes in the kidney were examined using hematoxylin and eosin (H&E) staining, electron microscopy, and immunohistochemical analysis. The molecular mechanisms underlying the protective effect of the combination pretreatment on kidney injury were investigated using enzyme-linked immunosorbent assay (ELISA) and Western blotting techniques.

RESULTS

The findings demonstrated that the combination therapy improved kidney function by attenuating pathological changes observed in H&E staining including tubular necrosis and glomerular damage, in addition to reducing levels of kidney function including serum levels of creatinine compared to the AMC group, blood urea nitrogen (BUN) uric acid, and albumin. Mean arterial blood pressure, and toxicity markers including Kidney Injury Molecule-1 (KIM-1), Cystatin-c were also decreased in samples of combination group compared to AMC group. Furthermore, the protective combination therapy downregulated NF-κB-p65, P53, Keap-1, and C-FOS, while upregulating Mammalian sirtuin 1 (SIRT1), inhibitor of nuclear factor kappa B (Iκβ), nuclear factor erythroid 2-related factor 2 (Nrf2), and Heme oxygenase-1 (HO-1) levels.

CONCLUSIONS

The findings reveal the potential clinical application of combining Diosmin and perindopril to reduce AMC-induced nephrotoxicity, which requires further research in clinical settings.

Aminoglycosides: Single- or Multiple-daily Dosing? An Updated Qualitative Systematic Review of Randomized Trials on Toxicity and Efficacy

INTRODUCTION

Aminoglycosides are among the first-choice antibiotics for routine clinical use. However, dose-limiting factors such as ototoxicity and nephrotoxicity are considered as serious complications of aminoglycosides.

OBJECTIVE

In this systematic review, the main goal was to investigate the efficacy and incidence of nephrotoxicity and ototoxicity of once-daily dosing (ODD) and multiple daily dosing (MDD) regimens of aminoglycosides through available randomized controlled trials (RCTs).

METHODS

We performed a literature-based research in relevant databases, including EMBASE, MEDLINE, and SCOPUS published between 1987 and 2023 using the keywords "aminoglycosides", "pharmacokinetics", "ODD", "MDD", "once daily", "multiple daily", "dosing regimen", "nephrotoxicity", "ototoxicity", "efficacy", "safety", and "toxicity". As so told, the results of this article were limited to papers available in English. Our initial search yielded 1124 results. After a review of the titles and abstracts of the articles, 803 articles were excluded from this study because they did not address the toxicity and effectiveness of ODD versus MDD of aminoglycosides. A total number of 20 studies on gentamicin, tobramycin, netilmicin, and amikacin met the inclusion criteria for the efficacy of aminoglycosides and their role in ototoxicity and nephrotoxicity were included in this review. Studies recruited different age classes, and the age of relevant cohorts varied from only a few days to more than 70 years.

RESULTS

The most common clinical condition in the included studies was cystic fibrosis.

CONCLUSION

In most studies, there were no significant differences between the two regimens regarding ototoxicity. In addition, the ODD regimens were safer than MDD concerning nephrotoxicity.

Improving the Safety of Clinical Management of COVID-19 Patients Receiving Aminoglycosides and Parenteral Nutrition: Y-site Compatibility Studies

PURPOSE

Aminoglycosides (AMGs) are broad-spectrum bactericidal antibiotics that can resolve bacterial infections co-existing with COVID-19 or exploit their potential antiviral activities. Patients presenting the most severe forms of COVID-19 due to escalating catabolism and significant lean body mass loss often require the concomitant administration of parenteral nutrition (PN) and antibiotics. The Y-site administration is one of the approaches allowing the co-administration of two intravenous medications in patients with limited vascular access. Our study aimed to investigate the compatibility of AMGs and selected commercial PN admixtures enriched in omega-3 fatty acids.

METHODS

Gentamycin (GM), amikacin (AM), and tobramycin (TM) solutions for infusion were combined with Nutriflex Omega Special (NOS) and Smofkabiven (SFK). Three different volume ratios were investigated: 1:2, 1:1, and 2:1, simulating Y-site administration. Samples underwent visual examination and determination of the lipid emulsion particle size, zeta potential, and pH immediately after preparation and after four hours of storage at room temperature (22 ± 2 °C) with sunlight exposure.

RESULTS

GM and AM combined with NOS in all studied ratios met the set-up acceptance criteria. The addition of TM to NOS in a 2:1 volume ratio and all tested AMGs to SFK in all studied combinations significantly influenced the stability of the oil-water system leading to the appearance of globules larger than 5 µm exceeding the pharmacopeial limit of 0.05% immediately after preparation or after four hours of storage.

CONCLUSION

In conclusion, our study showed that NOS was less prone to destabilization of oil-in-water systems by AMGs than SFK. In justified clinical cases, due to the lack of appearance of precipitate or enlarged lipid droplets, the combined administration of GM and AM with the NOS could be considered, provided tested volume ratios of the drug and MCB in the infusion line are maintained. However, it should be noted that such an infusion may be associated with the risk of changes in the pharmacokinetics of the drug.

The potential role of upregulated PARP-1/RIPK1 expressions in amikacin-induced oxidative damage and nephrotoxicity in Wistar rats

This study aimed to investigate the gene expression levels associated with nephrotoxic action of amikacin, as well as the post-treatment effect of diuretics on its nephrotoxic effects. Sixty male rats were divided equally into six groups, including the control group receiving saline intra-peritoneally (ip), and the five treated groups including therapeutic and double therapeutic dose groups, injected ip (15 and 30 mg/kg b.wt./day) respectively for seven days, and another two rat groups treated as therapeutic and double therapeutic dose groups then administered the diuretic orally for seven days and the last group received amikacin ip at a rate of 15 mg/kg/day for seven days, then given free access to water without diuretics for another seven days and was kept as a self-recovery group. Amikacin caused kidney injury, which was exacerbated by the double therapeutic dose, as evidenced by abnormal serum renal injury biomarkers, elevated renal MDA levels, inhibition of renal catalase and SOD enzyme activities, with renal degenerative and necrotic changes. Moreover, comet assays also revealed renal DNA damage. Interestingly, amikacin administration markedly elevated expression levels of the PARP-1, RIP1, TNF-α, IL-1β, and iNOS genes as compared to the control group. However, compared to the self-recovery group, post-amikacin diuretic treatment modulates amikacin-induced altered findings and alleviates amikacin nephrotoxic effects more efficiently. Our findings suggested the potential role of PARP-1 and RIPK1 expressions that influence the expression of proinflammatory cytokines such as IL-1β and TNF-α by exaggerating oxidative stress which may contribute to the pathogenesis of amikacin-induced nephrotoxicity.

Restoring susceptibility to aminoglycosides: identifying small molecule inhibitors of enzymatic inactivation

Growing resistance to antimicrobial medicines is a critical health problem that must be urgently addressed. Adding to the increasing number of patients that succumb to infections, there are other consequences to the rise in resistance like the compromise of several medical procedures and dental work that are heavily dependent on infection prevention. Since their introduction in the clinics, aminoglycoside antibiotics have been a critical component of the armamentarium to treat infections. Still, the increase in resistance and their side effects led to a decline in their utilization. However, numerous current factors, like the urgent need for antimicrobials and their favorable properties, led to renewed interest in these drugs. While efforts to design new classes of aminoglycosides refractory to resistance mechanisms and with fewer toxic effects are starting to yield new promising molecules, extending the useful life of those already in use is essential. For this, numerous research projects are underway to counter resistance from different angles, like inhibition of expression or activity of resistance components. This review focuses on selected examples of one aspect of this quest, the design or identification of small molecule inhibitors of resistance caused by enzymatic modification of the aminoglycoside. These compounds could be developed as aminoglycoside adjuvants to overcome resistant infections.

Predictive Performance of Population Pharmacokinetic Models for Amikacin in Term Neonates

BACKGROUND AND OBJECTIVE

Amikacin is preferred in treating Gram-negative infections in neonates and it has a narrow therapeutic window. The population pharmacokinetic modeling approach can aid in designing optimal dosage regimens for amikacin in neonates. In this study, we attempted to identify the suitable population pharmacokinetic model from the published reports for the study population from an Indian setting.

METHODS

Published population pharmacokinetic studies for amikacin in neonates were identified. Data on structural models and typical pharmacokinetic parameters were extracted from the studies. For the clinical study, neonates who met the inclusion criteria were enrolled in the study from the NICU, Kasturba Medical College, Manipal, during Jan 2020 to March 2022. Drug concentrations were estimated, and demographic and clinical data were collected. Identified population pharmacokinetic models were used to predict the amikacin concentrations in neonates. Predicted concentrations were compared against the observed concentrations. Differences between predicted and observed concentrations were quantified using statistical measures. The population pharmacokinetic model, which was able to predict the data well, is considered a suitable model for the study population. Dosing regimens were suggested for neonates using the pharmacometric simulation approach generated by the selected model.

RESULTS

A total of 43 plasma samples were collected from 31 neonates. Twelve population pharmacokinetic models were found for amikacin in neonates. The predictive performance of the 12 studies was performed using clinical data. A two-compartment model reported by Illamola et al. predicted the amikacin concentrations better than other models. Illamola et al. reported creatinine clearance and body weight as the significant covariates impacting the pharmacokinetic parameters of amikacin. This model was able to predict the clinical data with 29.97% and 0.686 of relative median absolute prediction error and relative root mean square error, respectively, which is the best among the published models. The Illamola et al. model was selected as the final model to perform pharmacometric simulations for the subjects with different combinations of creatinine clearance and body weight. Dosage regimens were designed to attain target therapeutic concentrations for the virtual subjects and a nomogram was developed.

CONCLUSIONS

The population pharmacokinetic model reported by the Illamola et al. model was selected as the final model to explain the clinical data with the lowest relative median absolute prediction error and relative root mean square error when compared with other models. An amikacin nomogram was developed for the neonates whose creatinine clearance and body weight ranged between 10 and 90 mL/min and between 2 and 4 kg, respectively. A developed nomogram can assist clinicians to design an optimal dosage regimen of amikacin for term neonates.

ISCCM Guidelines on Acute Kidney Injury and Renal Replacement Therapy

Acute kidney injury (AKI) is a complex syndrome with a high incidence and considerable morbidity in critically ill patients. Renal replacement therapy (RRT) remains the mainstay of treatment for AKI. There are at present multiple disparities in uniform definition, diagnosis, and prevention of AKI and timing of initiation, mode, optimal dose, and discontinuation of RRT that need to be addressed. The Indian Society of Critical Care Medicine (ISCCM) AKI and RRT guidelines aim to address the clinical issues pertaining to AKI and practices to be followed for RRT, which will aid the clinicians in their day-to-day management of ICU patients with AKI.

HOW TO CITE THIS ARTICLE

Mishra RC, Sodhi K, Prakash KC, Tyagi N, Chanchalani G, Annigeri RA, et al. ISCCM Guidelines on Acute Kidney Injury and Renal Replacement Therapy. Indian J Crit Care Med 2022;26(S2):S13-S42.

Population Pharmacokinetics and Dosing Optimization of Gentamicin in Critically Ill Patients Undergoing Continuous Renal Replacement Therapy

Purpose

Appropriate gentamicin dosing in continuous renal replacement therapy (CRRT) patients remains undefined. This study aimed to develop a population pharmacokinetic (PK) model of gentamicin in CRRT patients and to infer the optimal dosing regimen for gentamicin.

Methods

Fourteen CRRT patients dosed with gentamicin were included to establish a population PK model to characterize the variabilities and influential covariates of gentamicin. The pharmacokinetic/pharmacodynamic (PK/PD) target attainment and risk of toxicity for different combinations of gentamicin regimens (3–7 mg/kg q24h) and CRRT effluent doses (30–50 mL/h/kg) were evaluated by Monte Carlo simulation. The probability of target attainment (PTA) was determined for the PK/PD indices of the ratio of drug peak concentration/minimum inhibitory concentration (C_max/MIC > 10) and the ratio of area under the drug concentration–time curve/MIC over 24 h (AUC_0-24h/MIC > 100), and the risk of toxicity was estimated by drug trough concentration thresholds (1 and 2 mg/L).

Results

A one-compartment model adequately described the PK characteristics of gentamicin. Covariates including body weight, age, gender, and CRRT modality did not influence the PK parameters of gentamicin based on our dataset. All studied gentamicin regimens failed to achieve satisfactory PTAs for pathogens with an MIC ≥2 mg/L. A good balance of PK/PD target attainment and risk of toxicity (>2 mg/L) was achieved under 7 mg/kg gentamicin q24h and 40 mL/kg/h CRRT dose for an MIC ≤1 mg/L. CRRT dose intensity had a significant impact on the target attainment of AUC_0-24h/MIC >100 and risk of toxicity.

Conclusion

A combination of 7 mg/kg gentamicin q24h and 40 mL/kg/h CRRT dose might be considered as a starting treatment option for CRRT patients, and drug monitoring is required to manage toxicity.

Breaking the barriers for the delivery of amikacin: Challenges, strategies, and opportunities

Hypodermic delivery of amikacin is a widely adopted treatment modality for severe infections, including bacterial septicemia, meningitis, intra-abdominal infections, burns, postoperative complications, and urinary tract infections in both paediatric and adult populations. In most instances, the course of treatment requires repeated bolus doses of amikacin, prolonged hospitalization, and the presence of a skilled healthcare worker for administration and continuous therapeutic monitoring to manage the severe adverse effects. Amikacin is hydrophilic and exhibits a short half-life, which further challenges the delivery of sufficient systemic concentrations when administered by the oral or transdermal route. In this purview, the exploitation of novel controlled and sustained release drug delivery platforms is warranted. Furthermore, it has been shown that novel delivery systems are capable of increasing the antibacterial activity of amikacin at lower doses when compared to the conventional formulations and also aid in overcoming the development of drug-resistance, which currently is a significant threat to the healthcare system worldwide. The current review presents a comprehensive overview of the developmental history of amikacin, the mechanism of action in virulent strains as well as the occurrence of resistance, and various emerging drug delivery solutions developed both by the academia and the industry. The examples outlined within the review provides significant pieces of evidence on novel amikacin formulations in the field of antimicrobial research paving the path for future therapeutic interventions that will result in improved clinical outcome.

Liquid chromatography-tandem mass spectrometry method for quantification of gentamicin and its individual congeners in serum and comparison results with two immunoanalytical methods (fluorescence polarization immunoassay and chemiluminiscent microparticle immunoassay)

BACKGROUND

Total gentamicin is a sum of five congeners C1, C1a, C2, C2a and minor C2b, which differ from each other in their methylation on the purpurosamine ring. Liquid chromatography with mass detection (LC-MS/MS) and specified calibration material enables the concentration of total gentamicin and its individual congeners to be analysed.

METHODS

50 µL serum was precipitated with acetonitrile in the presence of 0.5 mol/L formic acid. A RP BEH C18 1.7 µm 2.1x50 mm column maintained at 30 °C and tobramicin as the internal standard were used. Mass detection was performed in positive electrospray. The gentamicin results were compared with fluorescence polarization immunoassay (FPIA) and chemiluminiscent microparticle immunoassay (CMIA). Passing-Bablock regression analysis and Bland-Altman analysis were used.

RESULTS

Calibration curves for individual gentamicin congeners were linear with correlation coefficients between 0.997 and 0.998. Recovery was 91.6-102.0% and the coefficients of variation 1.4-8.4%. The total gentamicin concentration was compared with immunoassay FPIA (LC-MS_gen = 0.9798xPFIA_gen) and CMIA (LC MS_gen = 0.9835xCMIA_gen) both with significant correlation (p < 0.001).

CONCLUSION

The LC-MS/MS method is fast and precise and can be applied to routine TDM in patients. Comparing it to immunoassays makes it possible to measure concentration of gentamicin congeners, which may be important in the case of their different pharmacokinetics.

Prior Antibiotic Therapy and the Onset of Healthcare-Associated Infections Sustained by Multidrug-Resistant Klebsiella pneumoniae in Intensive Care Unit Patients: A Nested Case-Control Study

Epidemiological research has demonstrated direct relationships between antibiotic consumption and the emergence of multidrug-resistant (MDR) bacteria. In this nested case-control study, we assessed whether prior exposure to antibiotic therapy and its duration affect the onset of healthcare-associated infections (HAIs) sustained by MDR Klebsiella pneumoniae (MDR-Kp) in intensive care unit patients. Cases were defined as patients who developed an MDR-Kp HAI. Controls matched on sex and the length of intensive care unit (ICU) stay were randomly selected from the at-risk population. Any antibiotic agent received in systemic administration before the onset of infection was considered as antibiotic exposure. Multivariable conditional logistic regression analyses were performed to estimate the effect of prior exposure to each antibiotic class (Model 1) or its duration (Model 2) on the onset of HAIs sustained by MDR-Kp. Overall, 87 cases and 261 gender-matched controls were compared. In Model 1, aminoglycosides and linezolid independently increased the likelihood of developing an MDR-Kp HAI, whereas exposure to both linezolid and penicillins reduced the effect of linezolid alone. In Model 2, cumulative exposure to aminoglycosides increased the likelihood of the outcome, as well as cumulative exposures to penicillins and colistin, while a previous exposure to both penicillins and colistin reduced the influence of the two antibiotic classes alone. Our study confirms that aminoglycosides, penicillins, linezolid, and colistin may play a role in favoring the infections sustained by MDR-Kp. However, several double exposures in the time window before HAI onset seemed to hinder the selective pressure exerted by individual agents.

Aminoglycoside use and intensive care unit-acquired weakness: A systematic review and meta-analysis

Background

The relationship between aminoglycoside use and intensive care unit (ICU)-acquired weakness remains controversial. In the present study, we performed a systematic review and meta-analysis to examine the relationship between aminoglycoside use and ICU-acquired weakness in critically ill patients.

Methods

The PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials and Cumulative Index of Nursing and Allied Health Literature databases were searched from the earliest available date to July 10, 2019. Randomized controlled trials and prospective cohort studies examining the relationship between aminoglycosides and ICU-acquired weakness in adult ICU patients were included. Two authors independently screened titles/abstracts, reviewed full text and extracted data from the included studies. We performed the Meta-analysis using Stata version 15.0 and used the DerSimonian-Laird random effects model for data analyses. Heterogeneity was evaluated using the χ² statistic and I² statistic. Publication bias was evaluated with funnel plots qualitatively, the Begg’s test and Egger’s test quantitatively.

Results

Ten prospective cohort studies were included and analysed in this review. The overall effect sizes of the studies revealed a statistically significant relationship between aminoglycoside use and ICU-acquired weakness (OR, 2.06; 95%CI, 1.33–3.21; I² = 56%). Subgroup and sensitivity analyses suggested a significant association between aminoglycoside use and studies limited to patients with clinical weakness (OR, 2.74; 95%CI, 1.83–4.10; I² = 0%), and not to studies limited to patients with abnormal electrophysiology (OR, 1.78; 95%CI, 0.94–3.39; I² = 59%), a large sample size (OR, 1.81; 95%CI, 0.97–3.39; I² = 75%), or low risk of bias (OR, 1.59; 95%CI, 0.97–2.60; I² = 56%); however, statistical heterogeneity was obvious. There were no significant publication biases found in the review.

Conclusions

The review revealed a significant relationship between aminoglycoside use and ICU-acquired weakness.

Is gentamicin administered to individual patients in optimal doses already at the beginning of therapy?

Introduction A gentamicin dose, which the physicians select, frequently does not take any pharmacokinetic parameters into consideration.

Aim To analyse the results of therapeutic drug monitoring (TDM) of gentamicin for those patients who have not had the gentamicin dose adjusted at the beginning of therapy (first group) and for those patients who had the gentamicin dose adjusted at the beginning of therapy (second group).

Methods We acquired the basic data about patients from the requests for laboratory examination of levels of gentamicin. We measured all the gentamicin concentrations mentioned in this work using the FPIA method.

Results The monitored set included 379 hospitalized patients during a 4-year period. We divided the monitored set into 2 groups. First group was composed of patients without dose adjustment of gentamicin at the beginning of therapy, and the second group was composed of patients with dose adjustment of gentamicin by the clinical pharmacist at the beginning of therapy. In addition, the patients in each group were divided according to the body mass index (BMI). In the first group of patients, a low percentage of patients had both optimal levels (trough, peak levels). As for patients with BMI > 25 m2/kg, there were only 17 % such cases, and the patients with BMI ≤ 25 m2/kg were only 18.8 %. In the second group, the patients had all trough and peak levels in optimal therapeutic range at obese patients, overweight patients and also at patients with normal weight (p < 0.001).

Conclusion Adjustment of dosage regimens immediately at the beginning of therapy will provide for administering sufficient doses of antibiotics at the beginning of therapy, which is a pre-condition for a successful anti-infective therapy. Therapeutic monitoring of levels allows for administration of sufficient dose of gentamicin without fear of any undesirable effects.

Considerations for Medications Commonly Utilized in the Oncology Population in the Intensive Care Unit

An increasing number of oncologic patients are presenting to the intensive care unit with complications from both their chronic disease states and cancer therapies due to improved survival rates. The management of these patients is complex due to immunosuppression (from the malignancy and/or treatment), metabolic complications, and diverse medication regimens with the potential for significant drug-drug interactions and overlapping adverse effects. This chapter will provide clinicians with an overview of non-chemotherapy medications frequently encountered in the critically ill oncologic patient, with a focus on practical considerations.

Purinergic Signaling and Cochlear Injury-Targeting the Immune System?

Hearing impairment is the most common sensory deficit, affecting more than 400 million people worldwide. Sensorineural hearing losses currently lack any specific or efficient pharmacotherapy largely due to the insufficient knowledge of the pathomechanism. Purinergic signaling plays a substantial role in cochlear (patho)physiology. P2 (ionotropic P2X and the metabotropic P2Y) as well as adenosine receptors expressed on cochlear sensory and non-sensory cells are involved mostly in protective mechanisms of the cochlea. They are implicated in the sensitivity adjustment of the receptor cells by a K⁺ shunt and can attenuate the cochlear amplification by modifying cochlear micromechanics. Cochlear blood flow is also regulated by purines. Here, we propose to comprehend this field with the purine-immune interactions in the cochlea. The role of harmful immune mechanisms in sensorineural hearing losses has been emerging in the horizon of cochlear pathologies. In addition to decreasing hearing sensitivity and increasing cochlear blood supply, influencing the immune system can be the additional avenue for pharmacological targeting of purinergic signaling in the cochlea. Elucidating this complexity of purinergic effects on cochlear functions is necessary and it can result in development of new therapeutic approaches in hearing disabilities, especially in the noise-induced ones.

Vancomycin Therapeutic Regime Adjustment in Newborns and Infants with Bacterial Infection: Case Series

Background:

Vancomycin is used mostly to overcome infections caused by methicillinresistant microorganisms. There are no well-established administration protocols for neonates and infants, so the leak of a specific administration regime in that population may lead to serum concentrations beyond the specified range.

Objective:

This case series evaluated the pharmacokinetics adjustment from a vancomycin therapeutic regimen prescribed to neonates and infants with bacterial infection at a neonatal public hospital intensive- care-unit, with the primary purpose to verify cases of nephrotoxicity.

Methods:

Three neonates and four infants taking vancomycin therapy, hospitalized in a public hospital from November 2014 to March 2015, were included in the study. Vancomycin serum concentrations were determined by particle-enhanced-turbidimetric inhibition-immunoassay. The vancomycin concentrations were used for dose adjustment by USC*Pack-PC-Collection®, a non-parametric maximization program. The trough serum concentration range of 10 to 20mg.L-1 was considered therapeutic.

Results:

Three patients had serum concentration outside the reference-range, one with subtherapeutic, and two with supratherapeutic concentrations. All patients had concomitant use of drugs which interfered with vancomycin distribution and excretion pharmacokinetics parameters, including drugs that may enhance nephrotoxicity. One patient showed signs of acute renal damage, by low vancomycin and creatinine estimated clearances.

Conclusion:

The pharmacokinetic adjustment has been proven to be a useful and necessary tool to increase therapeutic efficacy and treatment benefits. The standard dose of vancomycin can be used to initiate therapy in neonates and infants admitted to the ICU, but after reaching the drug steady state, the dosing regimen should be individualized and guided by pharmacokinetic parameters.

Pharmacokinetic and Pharmacodynamic Considerations of Antibiotics of Last Resort in Treating Gram-Negative Infections in Adult Critically Ill Patients

PURPOSE OF REVIEW

We provide an overview of antimicrobials that are considered last resort for the treatment of resistant gram-negative infections in adult critically ill patients. The role in therapy, pharmacodynamic (PD) goals, and pharmacokinetic (PK) changes in critical illness for aminoglycosides, polymyxins, tigecycline, fosfomycin, and fluoroquinolones are summarized.

RECENT FINDINGS

Altered PK in septic patients in the intensive care unit (ICU) is observed with many of our agents of last resort. Based on the available literature, dosage adjustments may be required to optimize PK parameters and meet PD targets for most effective bacterial killing. Data is limited, studies are conducted in heterogeneous patient populations, and conclusions are frequently conflicting. Strategic dosing regimens such as high-dose extended interval dosing of aminoglycosides or loading doses with colistin and polymyxin B are examples of ways to optimize antibiotic PK in critically ill patients. Benefits of these strategies must be balanced with risks of increased toxicity. Patients with resistant gram-negative infections may present with septic shock in the ICU. Sepsis can significantly alter the PK of antibiotics and require dosage adjustments to attain optimal drug levels. An understanding of PK and PD properties of these agents of last resort will help to maximize therapeutic efficacy while minimizing toxic effects.

Amikacin: Uses, Resistance, and Prospects for Inhibition

Aminoglycosides are a group of antibiotics used since the 1940s to primarily treat a broad spectrum of bacterial infections. The primary resistance mechanism against these antibiotics is enzymatic modification by aminoglycoside-modifying enzymes that are divided into acetyl-transferases, phosphotransferases, and nucleotidyltransferases. To overcome this problem, new semisynthetic aminoglycosides were developed in the 70s. The most widely used semisynthetic aminoglycoside is amikacin, which is refractory to most aminoglycoside modifying enzymes. Amikacin was synthesized by acylation with the l-(-)-γ-amino-α-hydroxybutyryl side chain at the C-1 amino group of the deoxystreptamine moiety of kanamycin A. The main amikacin resistance mechanism found in the clinics is acetylation by the aminoglycoside 6'-N-acetyltransferase type Ib [AAC(6')-Ib], an enzyme coded for by a gene found in integrons, transposons, plasmids, and chromosomes of Gram-negative bacteria. Numerous efforts are focused on finding strategies to neutralize the action of AAC(6')-Ib and extend the useful life of amikacin. Small molecules as well as complexes ionophore-Zn⁺² or Cu⁺² were found to inhibit the acetylation reaction and induced phenotypic conversion to susceptibility in bacteria harboring the aac(6')-Ib gene. A new semisynthetic aminoglycoside, plazomicin, is in advance stage of development and will contribute to renewed interest in this kind of antibiotics.

Endotoxemia-mediated inflammation potentiates aminoglycoside-induced ototoxicity

The ototoxic aminoglycoside antibiotics are essential to treat severe bacterial infections, particularly in neonatal intensive care units. Using a bacterial lipopolysaccharide (LPS) experimental model of sepsis, we tested whether LPS-mediated inflammation potentiates cochlear uptake of aminoglycosides and permanent hearing loss in mice. Using confocal microscopy and enzyme-linked immunosorbent assays, we found that low-dose LPS (endotoxemia) greatly increased cochlear concentrations of aminoglycosides and resulted in vasodilation of cochlear capillaries without inducing paracellular flux across the blood-labyrinth barrier (BLB) or elevating serum concentrations of the drug. Additionally, endotoxemia increased expression of both serum and cochlear inflammatory markers. These LPS-induced changes, classically mediated by Toll-like receptor 4 (TLR4), were attenuated in TLR4-hyporesponsive mice. Multiday dosing with aminoglycosides during chronic endotoxemia induced greater hearing threshold shifts and sensory cell loss compared to mice without endotoxemia. Thus, endotoxemia-mediated inflammation enhanced aminoglycoside trafficking across the BLB and potentiated aminoglycoside-induced ototoxicity. These data indicate that patients with severe infections are at greater risk of aminoglycoside-induced hearing loss than previously recognized.

Gentamicin differentially alters cellular metabolism of cochlear hair cells as revealed by NAD(P)H fluorescence lifetime imaging

Aminoglycoside antibiotics are implicated as culprits of hearing loss in more than 120,000 individuals annually. Research has shown that the sensory cells, but not supporting cells, of the cochlea are readily damaged and/or lost after use of such antibiotics. High-frequency outer hair cells (OHCs) show a greater sensitivity to antibiotics than high- and low-frequency inner hair cells (IHCs). We hypothesize that variations in mitochondrial metabolism account for differences in susceptibility. Fluorescence lifetime microscopy was used to quantify changes in NAD(P)H in sensory and supporting cells from explanted murine cochleae exposed to mitochondrial uncouplers, inhibitors, and an ototoxic antibiotic, gentamicin (GM). Changes in metabolic state resulted in a redistribution of NAD(P)H between subcellular fluorescence lifetime pools. Supporting cells had a significantly longer lifetime than sensory cells. Pretreatment with GM increased NAD(P)H intensity in high-frequency sensory cells, as well as the NAD(P)H lifetime within IHCs. GM specifically increased NAD(P)H concentration in high-frequency OHCs, but not in IHCs or pillar cells. Variations in NAD(P)H intensity in response to mitochondrial toxins and GM were greatest in high-frequency OHCs. These results demonstrate that GM rapidly alters mitochondrial metabolism, differentially modulates cell metabolism, and provides evidence that GM-induced changes in metabolism are significant and greatest in high-frequency OHCs.

Therapeutic drug monitoring of amikacin in septic patients

INTRODUCTION

Use of higher than standard doses of amikacin (AMK) has been proposed during sepsis, especially to treat less susceptible bacterial strains. However, few data are available on drug concentrations during prolonged therapy and on potential adverse events related to this strategy.

METHODS

Sixty-three critically ill patients who required AMK administration for the treatment of severe infection were included in this study. After a loading dose (LD, 18 to 30 mg/kg), the daily regimen was adapted using therapeutic drug monitoring (TDM) of both peak (Cpeak) and trough (Cmin) concentrations. Target concentrations had to give a ratio of at least 8 between Cpeak and the minimal inhibitory concentration (MIC) of the isolated pathogen. A Cmin >5 mg/L was considered as potentially nephrotoxic. We recorded clinical and microbiological responses, the development of acute kidney injury (AKI) during therapy and ICU mortality.

RESULTS

The median AMK LD was 1500 (750 to 2400) mg, which resulted in a Cpeak/MIC ≥8 in 40 (63%) patients. Increasing the dose in the 23 patients with a Cpeak/MIC <8 resulted in optimal Cpeak/MIC in 15 of these patients (79%). In 23 patients (37%), Cmin was >5 mg/L after the LD, notably in the presence of altered renal function at the onset of therapy, needing prolongation of drug administration. Overall, only 11 patients (17%) required no dose or interval adjustment during AMK therapy. Clinical cure (32/37 (86%) vs. 16/23 (70%), P = 0.18)) and microbiological eradication (29/35 (83%) vs. 14/23 (61%), P = 0.07) were higher in patients with an initial optimal Cpeak/MIC than in the other patients. The proportion of patients with clinical cure significantly improved as the Cpeak/MIC increased (P = 0.006). Also, increased time to optimal Cpeak was associated with worse microbiological and clinical results. AKI was identified in 15 patients (24%) during AMK therapy; 12 of these patients already had altered renal function before drug administration. Survivors (n = 47) had similar initial Cpeak/MIC ratios but lower Cmin values compared to nonsurvivors.

CONCLUSIONS

TDM resulted in adjustment of AMK therapy in most of our septic patients. Early achievement of an optimal Cpeak/MIC ratio may have an impact on clinical and microbiological responses, but not on outcome. In patients with impaired renal function prior to treatment, AMK therapy may be associated with a further decline in renal function.

Evaluating amikacin dosage regimens in intensive care unit patients: a pharmacokinetic/pharmacodynamic analysis using Monte Carlo simulation

The objectives of this study were to conduct a comparative pharmacokinetic/pharmacodynamic (PK/PD) evaluation using Monte Carlo simulation of conventional versus high-dose extended-interval dosage (HDED) regimens of amikacin (AMK) in intensive care unit (ICU) patients for an Acinetobacter baumannii infection model. The simulation was performed in five populations (a control population and four subpopulations of ICU patients). Using a specific AMK PK/PD model and Monte Carlo simulation, the following were generated: simulated AMK steady-state plasma level curves; PK/PD efficacy indexes [time during which the serum drug concentration remains above the minimum inhibitory concentration (MIC) for a dosing period (%T>MIC) and ratio of peak serum concentration to MIC (Cmax/MIC)]; evolution of bacterial growth curves; and adaptive resistance to treatment. A higher probability of bacterial resistance was observed with the HDED regimen compared with the conventional dosage regimen. A statistically significant increase in Cmax/MIC and a statistically significant reduction in %T>MIC with the HDED regimen were obtained. A multiple linear relationship between CFU values at 24h with Cmax/MIC and %T>MIC was obtained. In conclusion, with the infection model tested, the likelihood of resistance to treatment may be higher against pathogens with a high MIC with the HDED regimen, considering that in many ICU patients the %T>MIC may be limited. If a sufficient value of %T>MIC (≥60%) is not reached, even though the Cmax/MIC is high, the therapeutic efficacy of the treatment may not be guaranteed. This study indicates that different AMK dosing strategies could directly influence the efficacy results in ICU patients.

Gentamicin in hemodialyzed critical care patients: early dialysis after administration of a high dose should be considered

Gentamicin is a widely used antibiotic in the intensive care unit (ICU). Its dosage is difficult to adapt to hemodialyzed ICU patients. The FDA-approved regimen consists of the administration of 1 to 1.7 mg/kg of gentamicin at the end of each dialysis session. Better pharmacokinetic management could be obtained if gentamicin were administered just before the dialysis session. We performed Monte Carlo simulations (MCS) to determine the best gentamicin pharmacokinetic profile (high peak and low trough concentrations). Then, 6 mg/kg of gentamicin was infused into 10 ICU patients over a period of 30 min. A 4-h-long hemodialysis session was started 30 min after the end of the infusion. Pharmacokinetic samples were regularly collected over 24 h. A one-compartment model with zero-order input and first-order elimination was developed in Nonmem version VI to analyze patients' measured gentamicin concentration-versus-time profiles. Finally, additional MCS were performed to compare the regimen chosen with the FDA-approved gentamicin regimen. High peak concentrations (C(max), 31.8 ± 16.8 mg/liter) were achieved. The estimated C(24) and C(48) values (concentrations 24 and 48 h, respectively, after the beginning of the infusion) were 4.1 ± 2.3 and 1.8 ± 1.2 mg/liter, respectively. The volume of distribution was 0.21 ± 0.06 liter/kg. MCS confirmed that the dosing regimen chosen achieved the target C(max) whereas the FDA-approved regimen did not (31.0 ± 10.9 versus 8.8 ± 3.1 mg · liter(-1)). Moreover, the C(24) values were similar while the AUC(0-24) values were moderately increased (190.8 ± 65.0 versus 135 ± 42.2 mg · h · liter(-1)). Therefore, administration of 6 mg/kg of gentamicin before hemodialysis to critically ill patients achieves a high C(max) and an acceptable AUC, maximizing pharmacokinetic/pharmacodynamic endpoints.

Introduction to drug pharmacokinetics in the critically ill patient

Despite regular use of drugs for critically ill patients, overall data are limited regarding the impact of critical illness on pharmacokinetics (PK). Designing safe and effective drug regimens for patients with critical illness requires an understanding of PK. This article reviews general principles of PK, including absorption, distribution, metabolism, and elimination, and how critical illness can influence these parameters. In the area of drug absorption, we discuss the impact of vasopressor use, delayed gastric emptying and feeding tubes, and nutrient interactions. On the topic of drug distribution, we review fluid resuscitation, alterations in plasma protein binding, and tissue perfusion. With drug metabolism, we discuss hepatic enzyme activity, protein binding, and hepatic blood flow. Finally, we review drug elimination in the critically ill patient and discuss the impact of augmented renal clearance and acute kidney injury on drug therapies. In each section, we highlight select literature reviewing the PK impact of these conditions on a drug PK profile and, where appropriate, provide general suggestions for clinicians on how to modify drug regimens to manage PK challenges.

Pharmacokinetics and safety of single and multiple doses of ACHN-490 injection administered intravenously in healthy subjects

ACHN-490 is an aminoglycoside with activity against multidrug-resistant pathogens, including those resistant to currently used aminoglycosides. Two randomized, double-blind, placebo-controlled clinical studies investigated the pharmacokinetics (PK), safety, and tolerability of ACHN-490 injection in healthy subjects. Study 1 used a parallel-group design with escalating single (SD) and multiple doses (MD). Study 2 explored a longer duration of the highest dose tolerated in the first study. Subjects were randomly assigned to receive either ACHN-490 injection or a placebo administered by a 10-min intravenous infusion. Study 1 enrolled 39 subjects (30 active and 9 placebo) and consisted of a single dose of 1 mg/kg body weight followed by ascending SD and MD cohorts of 4, 7, 11, and 15 mg/kg for 10, 10, 5, and 3 days, respectively. Study 2 enrolled 8 subjects (6 active and 2 placebo) who received 15 mg/kg for 5 days. Safety was assessed from adverse event (AE) reporting, standard clinical laboratory procedures, and testing for renal, cochlear, and vestibular function. ACHN-490 exhibited linear and dose-proportional PK, with agreement between the studies for PK parameters assessed. The 15-mg/kg dose did not accumulate with repeated dosing over 5 days. Mean steady-state (±standard deviation) area under the concentration-time curve from 0 to 24 h (AUC(0-24)), maximum concentration of drug in serum (C(max)), half-life (t(1/2)), clearance, and volume of distribution at steady state (V(ss)) for the 15-mg/kg, day 5 dose were 239 ± 45 h·mg/liter, 113 ± 17 mg/liter, 3 ± 0.3 h, 1.1 ± 0.1 ml/min/kg, and 0.24 ± 0.04 liters/kg, respectively. AEs were mild to moderate and rapidly resolved. No evidence of nephrotoxicity or ototoxicity was observed.

New developments in aminoglycoside therapy and ototoxicity

After almost seven decades in clinical use, aminoglycoside antibiotics still remain indispensible drugs for acute infections and specific indications such as tuberculosis or the containment of pseudomonas bacteria in patients with cystic fibrosis. The review will describe the pathology and pathophysiology of aminoglycoside-induced auditory and vestibular toxicity in humans and experimental animals and explore contemporary views of the mechanisms of cell death. It will also outline the current state of protective therapy and recent advances in the development of aminoglycoside derivatives with low toxicity profiles for antimicrobial treatment and for stop-codon suppression in the attenuation of genetic disorders.