Aminoglycoside Pharmacodynamics

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.

Drug Therapies Affecting Renal Function: An Overview

Undesirable side effects of medication are inevitable. Due to the role of the kidneys in clearance and filtration, the renal system faces a unique situation when it comes to the side effects of drugs. It has an important role for different classes of drugs to be excreted, and drugs are a key factor for this system to be at risk. Medications in articles were divided into classes using the standard set by the Saudi Pharmaceutical Journal. Many drug classes cause renal insults. The top six classes were pain killers, antibiotics, proton pump inhibitors, antidiabetics, antihyperlipidemics, and agents for erectile dysfunction. Renal insults caused by these agents could vary in severity. Some drugs could cause nephrotoxicity from one dose, while others may only need continuous monitoring. Different populations also operate under different rules, as some people need dose adjustments while others who are medically free of major illnesses do not. A variety of unfavorable outcomes for the kidney could take place, such as acute kidney injury, chronic kidney disease, and end-stage renal disease, and unfortunately, some of these issues could lead to the need for renal replacement therapies. The outcome of this review paper will help multidisciplinary physicians to understand the renal side effects of the most used drug classes in the Kingdom of Saudi Arabia, their destructive mechanisms, and most importantly, the clinical presentations of renal dysfunction in relation to each class. Emphasizing these adverse effects will prevent future unfavorable outcomes, especially in commonly used drugs that are frequently prescribed for different age groups. Moreover, some of these drugs are considered to be over-the-counter medications, which makes them a serious problem that needs to be handled cautiously.

Antibiotic Distribution into Cerebrospinal Fluid: Can Dosing Safely Account for Drug and Disease Factors in the Treatment of Ventriculostomy-Associated Infections?

Ventriculostomy-associated infections, or ventriculitis, in critically ill patients are associated with considerable morbidity. Efficacious antibiotic dosing for the treatment of these infections may be complicated by altered antibiotic concentrations in the cerebrospinal fluid due to variable meningeal inflammation and antibiotic properties. Therefore, doses used to treat infections with a higher degree of meningeal inflammation (such as meningitis) may often fail to achieve equivalent exposures in patients with ventriculostomy-associated infections such as ventriculitis. This paper aims to review the disease burden, infection rates, and common pathogens associated with ventriculostomy-associated infections. This review also seeks to describe the disease- and drug-related factors that influence antibiotic distribution into cerebrospinal fluid and provide a critical appraisal of current dosing of antibiotics commonly used to treat these types of infections. A Medline search of relevant articles was conducted and used to support a review of cerebrospinal fluid penetration of vancomycin, including critical appraisal of the recent paper by Beach et al. recently published in this journal. We found that in the intensive care unit, ventriculostomy-associated infections are the most common and serious complication of external ventricular drain insertion and often result in prolonged patient stay and increased healthcare costs. Reported infection rates are extremely variable (between 0 and 45%), hindered by the inherent diagnostic difficulty. Both Gram-positive and Gram-negative organisms are associated with such infections and the rise of multi-drug-resistant pathogens means that effective treatment is an ongoing challenge. Disease factors that may need to be considered are reduced meningeal inflammation and the presence of critical illness; drug factors include physiochemical properties, degree of plasma-protein binding, and affinity to active transporter proteins present in the blood-cerebrospinal fluid barrier. The relationship between cerebrospinal fluid antibiotic exposures in the setting of ventriculostomy-associated infection and clinical response has not been fully elucidated for many of the antibiotics commonly used in its treatment. More thorough and clinically relevant investigations are needed to better define blood pharmacokinetic/pharmacodynamics targets and optimal therapeutic exposures for treatment of ventriculostomy-associated infections. It is hoped that this future research will be able to provide clearer recommendations for clinicians frequently faced with dosing-related dilemmas when treating patients with these challenging infections.

Antimicrobial Resistance in Escherichia coli

Multidrug resistance in Escherichia coli has become a worrying issue that is increasingly observed in human but also in veterinary medicine worldwide. E. coli is intrinsically susceptible to almost all clinically relevant antimicrobial agents, but this bacterial species has a great capacity to accumulate resistance genes, mostly through horizontal gene transfer. The most problematic mechanisms in E. coli correspond to the acquisition of genes coding for extended-spectrum β-lactamases (conferring resistance to broad-spectrum cephalosporins), carbapenemases (conferring resistance to carbapenems), 16S rRNA methylases (conferring pan-resistance to aminoglycosides), plasmid-mediated quinolone resistance (PMQR) genes (conferring resistance to [fluoro]quinolones), and mcr genes (conferring resistance to polymyxins). Although the spread of carbapenemase genes has been mainly recognized in the human sector but poorly recognized in animals, colistin resistance in E. coli seems rather to be related to the use of colistin in veterinary medicine on a global scale. For the other resistance traits, their cross-transfer between the human and animal sectors still remains controversial even though genomic investigations indicate that extended-spectrum β-lactamase producers encountered in animals are distinct from those affecting humans. In addition, E. coli of animal origin often also show resistances to other-mostly older-antimicrobial agents, including tetracyclines, phenicols, sulfonamides, trimethoprim, and fosfomycin. Plasmids, especially multiresistance plasmids, but also other mobile genetic elements, such as transposons and gene cassettes in class 1 and class 2 integrons, seem to play a major role in the dissemination of resistance genes. Of note, coselection and persistence of resistances to critically important antimicrobial agents in human medicine also occurs through the massive use of antimicrobial agents in veterinary medicine, such as tetracyclines or sulfonamides, as long as all those determinants are located on the same genetic elements.