Clinical use of the fluoroquinolones

Salmonella Typhimurium alters galactitol metabolism under ciprofloxacin treatment to balance resistance and virulence

Ciprofloxacin-resistant Salmonella Typhimurium (S. Typhimurium) causes a significant health burden worldwide. A wealth of studies has been published on the contributions of different mechanisms to ciprofloxacin resistance in Salmonella spp. But we still lack a deep understanding of the physiological responses and genetic changes that underlie ciprofloxacin exposure. This study aims to know how phenotypic and genotypic characteristics are impacted by ciprofloxacin exposure, from ciprofloxacin-susceptible to ciprofloxacin-resistant strains in vitro. Here, we investigated the multistep evolution of resistance in replicate populations of S. Typhimurium during 24 days of continuously increasing ciprofloxacin exposure and assessed how ciprofloxacin impacts physiology and genetics. Numerous studies have demonstrated that RamA is a global transcriptional regulator that prominently perturbs the transcriptional landscape of S. Typhimurium, resulting in a ciprofloxacin-resistant phenotype appearing first; the quinolone resistance-determining region mutation site can only be detected later. Comparing the microbial physiological changes and RNA sequencing (RNA-Seq) results of ancestral and selectable mutant strains, the selectable mutant strains had some fitness costs, such as decreased virulence, an increase of biofilm-forming ability, a change of "collateral" sensitivity to other drugs, and inability to utilize galactitol. Importantly, in the ciprofloxacin induced, RamA directly binds and activates the gatR gene responsible for the utilization of galactitol, but RamA deletion strains could not activate gatR. The elevated levels of RamA, which inhibit the galactitol metabolic pathway through the activation of gatR, can lead to a reduction in the growth rate, adhesion, and colonization resistance of S. Typhimurium. This finding is supported by studies conducted in M9 medium as well as in vivo infection models.

IMPORTANCE

Treatment of antibiotic resistance can significantly benefit from a deeper understanding of the interactions between drugs and genetics. The physiological responses and genetic mechanisms in antibiotic-exposed bacteria are not well understood. Traditional resistance studies, often retrospective, fail to capture the entire resistance development process and typically exhibit unpredictable dynamics. To explore how clinical isolates of S. Typhimurium respond to ciprofloxacin, we analyzed their adaptive responses. We found that S. Typhimurium RamA-mediated regulation disrupts microbial metabolism under ciprofloxacin exposure, affecting genes in the galactitol metabolic pathways. This disruption facilitates adaptive responses to drug therapy and enhances the efficiency of intracellular survival. A more comprehensive and integrated understanding of these physiological and genetic changes is crucial for improving treatment outcomes.

Patient weight has diverse effects on the prescribing of different antibiotics to dogs

Introduction

Various factors including body weight-associated treatment cost may influence the probability of dispensing antibiotics to dogs in first-opinion practice, but their effect on specific drug choice remains unclear.

Methods

Multiple membership regression modeling was used to investigate the probability of dispensing 12 different antibiotics to dogs of different weights in the context of various disease presentations, using anonymized data obtained from electronic health records of 18 clinics between 2020 and 2022. Data from 14,259 dogs were analyzed.

Results

Treatment choice varied significantly with animal weight. Higher body weight was associated with an increased likelihood of dispensing lower cost antimicrobials such as amoxicillin and trimethoprim sulfonamide, while use of higher cost antimicrobials such as cefovecin was strongly biased to smaller animals. However, these effects were limited when restricted treatment options were available for the target condition.

Conclusion

This work demonstrates that anticipated financial costs may result in different treatment choices for canine patients depending on their body weight. Further work is needed to understand the impact of financial pressures on veterinarians' treatment choices, and the implications for the optimization of antimicrobial stewardship in first opinion practice.

Overview of Side-Effects of Antibacterial Fluoroquinolones: New Drugs versus Old Drugs, a Step Forward in the Safety Profile?

Antibacterial fluoroquinolones (FQs) are frequently used in treating infections. However, the value of FQs is debatable due to their association with severe adverse effects (AEs). The Food and Drug Administration (FDA) issued safety warnings concerning their side-effects in 2008, followed by the European Medicine Agency (EMA) and regulatory authorities from other countries. Severe AEs associated with some FQs have been reported, leading to their withdrawal from the market. New systemic FQs have been recently approved. The FDA and EMA approved delafloxacin. Additionally, lascufloxacin, levonadifloxacin, nemonoxacin, sitafloxacin, and zabofloxacin were approved in their origin countries. The relevant AEs of FQs and their mechanisms of occurrence have been approached. New systemic FQs present potent antibacterial activity against many resistant bacteria (including resistance to FQs). Generally, in clinical studies, the new FQs were well-tolerated with mild or moderate AEs. All the new FQs approved in the origin countries require more clinical studies to meet FDA or EMA requirements. Post-marketing surveillance will confirm or infirm the known safety profile of these new antibacterial drugs. The main AEs of the FQs class were addressed, highlighting the existing data for the recently approved ones. In addition, the general management of AEs when they occur and the rational use and caution of modern FQs were outlined.

Fluoroquinolones Hybrid Molecules as Promising Antibacterial Agents in the Fight against Antibacterial Resistance

The emergence of bacterial resistance has motivated researchers to discover new antibacterial agents. Nowadays, fluoroquinolones keep their status as one of the essential classes of antibacterial agents. The new generations of fluoroquinolones are valuable therapeutic tools with a spectrum of activity, including Gram-positive, Gram-negative, and atypical bacteria. This review article surveys the design of fluoroquinolone hybrids with other antibacterial agents or active compounds and underlines the new hybrids' antibacterial properties. Antibiotic fluoroquinolone hybrids have several advantages over combined antibiotic therapy. Thus, some challenges related to joining two different molecules are under study. Structurally, the obtained hybrids may contain a cleavable or non-cleavable linker, an essential element for their pharmacokinetic properties and mechanism of action. The design of hybrids seems to provide promising antibacterial agents helpful in the fight against more virulent and resistant strains. These hybrid structures have proven superior antibacterial activity and less susceptibility to bacterial resistance than the component molecules. In addition, fluoroquinolone hybrids have demonstrated other biological effects such as anti-HIV, antifungal, antiplasmodic/antimalarial, and antitumor activity. Many fluoroquinolone hybrids are in various phases of clinical trials, raising hopes that new antibacterial agents will be approved shortly.

Circumstances of the ambulatory prescription of quinolones in Urology and opportunities for intervention

INTRODUCTION AND OBJECTIVES

Antimicrobial stewardship programmes (AMSP) seldom focus on ambulatory prescribing. Our AMSP primarily supervises in-hospital prescribing, but as we aim to include the ambulatory setting, we sought opportunities for intervention on ambulatory quinolone prescription.

MATERIALS AND METHODS

We selected the prescriptions made by urologists during 2018 for analysis, and manually checked them for adequacy.

RESULTS

We analyzed 237 prescriptions. Of 136 therapeutic prescriptions, 18.4% had no reported diagnosis and 31.6% had no reported symptoms. Most patients (60.3%) did not have any urinalysis or urine culture; among those who had, 27.7% had a urinalysis not suggestive of urinary tract infection and 67.4% had a positive culture, 83.9% of which had a suitable oral alternative to quinolones. Antimicrobial therapy was not indicated in 13.9% of cases; when it was, quinolones were considered inadequate in 67.8% of cases. Incorrect duration was found in 51.1% of cases. Forty-six prescriptions were made for prophylaxis; all of these were considered inadequate.

CONCLUSION

We found a high prevalence of inadequate ambulatory quinolone prescriptions in Urology. Many followed incomplete recordings, lack of laboratory use, or inattention to alternatives. Treatment duration and quinolone choice were frequently inadequate. Quinolone prescribing for prophylaxis was always considered inadequate. These prescribing errors could serve as a starting point for future interventions.

Nanotechnology as a Novel Approach in Combating Microbes Providing an Alternative to Antibiotics

The emergence of infectious diseases promises to be one of the leading mortality factors in the healthcare sector. Although several drugs are available on the market, newly found microorganisms carrying multidrug resistance (MDR) against which existing drugs cannot function effectively, giving rise to escalated antibiotic dosage therapies and the need to develop novel drugs, which require time, money, and manpower. Thus, the exploitation of antimicrobials has led to the production of MDR bacteria, and their prevalence and growth are a major concern. Novel approaches to prevent antimicrobial drug resistance are in practice. Nanotechnology-based innovation provides physicians and patients the opportunity to overcome the crisis of drug resistance. Nanoparticles have promising potential in the healthcare sector. Recently, nanoparticles have been designed to address pathogenic microorganisms. A multitude of processes that can vary with various traits, including size, morphology, electrical charge, and surface coatings, allow researchers to develop novel composite antimicrobial substances for use in different applications performing antimicrobial activities. The antimicrobial activity of inorganic and carbon-based nanoparticles can be applied to various research, medical, and industrial uses in the future and offer a solution to the crisis of antimicrobial resistance to traditional approaches. Metal-based nanoparticles have also been extensively studied for many biomedical applications. In addition to reduced size and selectivity for bacteria, metal-based nanoparticles have proven effective against pathogens listed as a priority, according to the World Health Organization (WHO). Moreover, antimicrobial studies of nanoparticles were carried out not only in vitro but in vivo as well in order to investigate their efficacy. In addition, nanomaterials provide numerous opportunities for infection prevention, diagnosis, treatment, and biofilm control. This study emphasizes the antimicrobial effects of nanoparticles and contrasts nanoparticles' with antibiotics' role in the fight against pathogenic microorganisms. Future prospects revolve around developing new strategies and products to prevent, control, and treat microbial infections in humans and other animals, including viral infections seen in the current pandemic scenarios.

Fluoroquinolones: Blessings Or Curses

Fluoroquinolones are one of the world's most valuable and popularly used categories of antimicrobial agents. This paper attempts to review the substantial progress of fluoroquinolones from their discovery to black box warning. Antibiotic drug choice will remain difficult in the presence of increasing resistance, but the introduction of fluoroquinolones has created a new and exciting era in antimicrobial treatment. These are a synthetic heterogeneous group of compounds used in both hospital and community practices to treat numerous severe infections. The era of quinolone antibiotics began with the serendipitous discovery of the quinolone prototype in 1962. The chronological development of fluoroquinolone reported that nalidixic acid was the first quinolone that gained popular choice for the treatment of urinary tract infection. The subsequent agents like levofloxacin, ofloxacin, norfloxacin, gatifloxacin, moxifloxacin, clinafloxacin, sparfloxacin, and ciprofloxacin were derived through side chain and nuclear manipulation from basic pharmacophore. The fluoroquinolone motifs have been found as a milestone, effective in certain infections that are respiratory tract infection, urinary tract infection, bone disorders, meningococcal and mycobacterial infections, sexually transmitted diseases, skin infections, etc. Fluoroquinolones are first entirely man-made antibiotics that exhibit antibacterial activity through the inhibition of topoisomerase II, topoisomerase IV and deoxyribonucleic acid gyrase, which is vital for chromosome replication and function. The post-marketing surveillance pointed out the favorable side effects associated with fluoroquinolones such as phototoxicity, QT interval prolongation and anaphylaxis. The discovery, development and clinical use of fluoroquinolone antibiotics in the last century contributed to a decline in morbidity and mortality rates.

Analyzing Possible Native Functions of the Quinolone Resistance Gene qnr in Vibrio vulnificus

The worldwide distribution of qnr genes found on plasmids and their presence on the chromosomes of aquatic bacteria, such as Vibrio vulnificus, one of the suspected sources, suggests an origin before the development of synthetic quinolones. However, their native function remains unknown. Previous work indicated that expression of qnrVv in V. vulnificus was induced by cold shock. To investigate its role further, we constructed single in-frame deletion mutants in qnrVv and cspA (the gene for cold shock protein) and a double mutant in qnrVv and cspA in V. vulnificus ATCC 17562 to evaluate the response to different environmental conditions and stresses and to exposure to various DNA-damaging agents. We found that qnrVv is involved in resistance to ciprofloxacin, levofloxacin, and mitomycin C and in the cold shock response in V. vulnificus Moreover, ΔqnrVv and ΔcspA mutants showed slower growth when they were treated with bile salts at 37°C and then shifted to 15°C (cold shock) without bile salts in the medium, with the effect being stronger in the double mutant. This transition may mimic what happens when V. vulnificus is ingested into the gastrointestinal tract and released in its natural environment. Cold shock and bile salts induced the expression of cspA and DNA gyrase and topoisomerase IV genes. However, no induction was found in the ΔqnrVv mutant, suggesting that the qnrVv gene is involved in the response to DNA damage and nucleic acid secondary structure.

Molecular characterization of mutations associated with resistance to second line drugs in Mycobacterium tuberculosis patients from Casablanca, Morocco

The emergence and spread of extensively drug-resistant tuberculosis (XDR-TB) is a serious threat to global health. Therefore, its rapid diagnosis is crucial. The present study aimed to characterize mutations conferring resistance to second line drugs (SLDs) within multidrug Mycobacterium tuberculosis (MDR-MTB) isolates and to estimate the occurrence of XDR-TB in Casablanca, Morocco. A panel of 200 MDR-TB isolates was collected at the Pasteur Institute between 2015-2018. Samples were subjected to drug susceptibility testing to Ofloxacin (OFX), Kanamycin (KAN) and Amikacin (AMK). The mutational status of gyrA, gyrB, rrs, tlyA and eis was assessed by sequencing these target genes. Drug susceptibility testing for SLDs showed that among the 200 MDR strains, 20% were resistant to OFX, 2.5% to KAN and 1.5% to AMK. Overall, 14.5% of MDR strains harbored mutations in gyrA, gyrB, rrs and tlyA genes. From the 40 OFX^R isolates, 67.5% had mutations in QRDR of gyrA and gyrB genes, the most frequent one being Ala90Val in gyrA gene. Of note, none of the isolates harbored simultaneously mutations in gyrA and gyrB genes. In eight out of the 200 MDR-TB isolates resistant either to KAN or AMK, only 25% had A1401G or Lys89Glu change in rrs and tlyA genes respectively. This study is very informative and provides data on the alarming rate of fluoroquinolone resistance which warrants the need to implement appropriate drug regimens to prevent the emergence and spread of more severe forms of Mycobacterium tuberculosis drug resistance.

Fluoroquinolones suppress gluconeogenesis by inhibiting fructose 1,6-bisphosphatase in primary monkey hepatocytes

Dysglycemia is one of the most serious adverse events associated with the clinical use of certain fluoroquinolones. The purpose of this study was to investigate the effects of the representative fluoroquinolones moxifloxacin and gatifloxacin on hepatic gluconeogenesis using primary monkey hepatocytes. Glucose production was induced after the cells were incubated for 4 h with 10 mM sodium lactate and 1 mM sodium pyruvate as gluconeogenic substrates. Under these conditions, moxifloxacin and gatifloxacin dose-dependently suppressed gluconeogenesis at concentrations of 100 μM or higher. Transcriptome analysis of rate-limiting enzymes involved in hepatic gluconeogenesis revealed that moxifloxacin and gatifloxacin at a concentration of 1000 μM did not affect the expression of key gluconeogenic enzymes such as phosphoenolpyruvate carboxykinase, glucose 6-phosphatase, and fructose 1,6-bisphosphatase. Furthermore, metabolome analysis, in vitro glucose production assay using additional gluconeogenic substrates, and fructose 1,6-bisphosphatase assay using the cell extracts showed that fluoroquinolones enzymatically suppressed hepatic gluconeogenesis by inhibiting fructose 1,6-bisphosphatase. These inhibitory effects may involve in the clinically relevant dysglycemia associated with fluoroquinolones in human.

Antibacterial and Pharmacological Evaluation of Fluoroquinolones: A Chemoinformatics Approach

Fluoroquinolone (FQ) antibiotics are an important class of synthetic antibacterial agents. These are the most extensively used drugs for treating bacterial infections in the field of both human and veterinary medicine. Herein, the antibacterial and pharmacological properties of four fluoroquinolones: lomefloxacin, norfloxacin, ciprofloxacin, and ofloxacin have been studied. The objective of this study was to analyze the antibacterial characteristics of the different fluoroquinolones. Also, the pharmacological properties of the compounds including the Lipinski rule of five, absorption, distribution, metabolism, and excretion, LD50, drug likeliness, and toxicity were evaluated. We found that among all four FQ molecules, ofloxacin showed the highest antibacterial activity through in silico assays with a strong interaction (‒38.52 kJ/mol) with the antibacterial target protein (topoisomerase-II DNA gyrase enzyme). The pharmacological and pharmacokinetic analysis also showed that the compounds ciprofloxacin, ofloxacin, lomefloxacin and norfloxacin have good pharmacological properties. Notably, ofloxacin was found to possess an IGC50 (concentration needed to inhibit 50% growth) value of 0.286 μg/L against the Tetrahymena pyriformis protozoa. It also tested negative for the Ames toxicity test, showing its non-carcinogenic character.

Lack of phototoxicity potential with delafloxacin in healthy male and female subjects: comparison to lomefloxacin

AIMS

Delafloxacin is a fluoroquinolone antibiotic recently approved by the FDA for treatment of acute bacterial skin and skin structure infections (ABSSSI). Delafloxacin was assessed for phototoxicity potential compared with a known phototoxic fluoroquinolone.

METHODS

A Phase 1, investigator-blind, placebo/active-controlled, randomized, parallel-group study was conducted in 52 healthy male and female volunteers who received 200 or 400 mg of oral delafloxacin, 400 mg oral lomefloxacin or placebo once daily for 6 days. This study evaluated the photosensitizing potential and possible wavelength dependency of delafloxacin by comparing the response of the skin to ultraviolet A (UVA), ultraviolet B (UVB) and visible radiation prior to and during administration of delafloxacin, lomefloxacin as a positive control, or placebo. Adverse events were monitored throughout the study.

RESULTS

Forty-seven subjects completed six days of dosing, and no evidence of phototoxicity was seen with delafloxacin. Delafloxacin at 200 and 400 mg day-1 and placebo did not demonstrate differences in percent change from baseline in minimal erythema dose at all tested wavelengths (295-430 nm) by monochromator and solar simulator. Lomefloxacin, the positive control, had statistically significant differences (p < 0.05) at UVA wavelengths of 335 and 365 ± 30 nm 24 hours after radiation exposure (maximum response). The phototoxic index results were significantly higher for lomefloxacin at 335 nm and 365 nm compared to placebo and delafloxacin.

CONCLUSIONS

200 and 400 mg of delafloxacin administered for 6 days were well tolerated in healthy adult volunteers. Delafloxacin and placebo failed to demonstrate a phototoxic effect but lomefloxacin, the positive control, demonstrated moderate phototoxicity.

Design, synthesis, and evaluation of novel N-1 fluoroquinolone derivatives: Probing for binding contact with the active site tyrosine of gyrase

Structural studies of topoisomerase-fluoroquinolone-DNA ternary complexes revealed a cavity between the quinolone N-1 position and the active site tyrosine. Fluoroquinolone derivatives having positively charged or aromatic moieties extended from the N-1 position were designed to probe for binding contacts with the phosphotyrosine residue in ternary complex. While alkylamine, alkylphthalimide, and alkylphenyl groups introduced at the N-1 position afforded derivatives that maintained modest inhibition of the supercoiling activity of DNA gyrase, none retained ability to poison DNA gyrase. Thus, the addition of a large and/or long moiety at the N-1 position disrupts ternary complex formation, and retained ability to inhibit supercoiling is likely through interference with the strand breakage reaction. Two derivatives were found to possess inhibitory effects on the decatenation activity of human topoisomerase II.

Relationship Between Fluoroquinolone Structure and Neurotoxicity Revealed by Zebrafish Neurobehavior

Central nervous system side effects are one of the most frequently reported adverse reactions of fluoroquinolones (FQs). However, the mechanism is not fully understood. In this study, zebrafish ( Danio rerio) were used as a model system. We quantified neurobehavior by recording indicators with automated video-tracking and used liquid chromatography-tandem mass spectrometry to detect drug absorption in vivo. We studied embryotoxicity and effects on zebrafish locomotor activity of 17 typical FQs. In addition, we calculated the stable conformation of typical FQs in aqueous conditions. The relationships between structure, neurotoxicity, and embryotoxicity were analyzed. The results indicate: (1) The effects of FQs on zebrafish neurobehavior can be divided into four categories. Type I has no significant influence on locomotor activity. Type II suppresses locomotor activity. Type III inhibits at low concentration and stimulates at high concentration. Type IV stimulates and then suppresses (biphasic response). (2) Structural modifications of FQs can change toxicity properties in zebrafish. Cleavage of the C-7 piperazinyl structure decreases neurotoxicity but enhances embryotoxicity. The C-3 decarboxyl formation and 5-NH₂ derivatives might enhance embryotoxicity and neurotoxicity. (3) There are two toxic functional groups. The piperazinyl structure at position C-7 (toxic functional group I) can cause primary reactions which may be by the inhibition of γ-aminobutyric acid receptors, and the nucleus containing a carboxyl group at position 3 (toxic functional group II) might cause a reaction secondary to the effect of toxic functional group I and reverse its effects.

Ubiquitous Nature of Fluoroquinolones: The Oscillation between Antibacterial and Anticancer Activities

Fluoroquinolones are synthetic antibacterial agents that stabilize the ternary complex of prokaryotic topoisomerase II enzymes (gyrase and Topo IV), leading to extensive DNA fragmentation and bacteria death. Despite the similar structural folds within the critical regions of prokaryotic and eukaryotic topoisomerases, clinically relevant fluoroquinolones display a remarkable selectivity for prokaryotic topoisomerase II, with excellent safety records in humans. Typical agents that target human topoisomerases (such as etoposide, doxorubicin and mitoxantrone) are associated with significant toxicities and secondary malignancies, whereas clinically relevant fluoroquinolones are not known to exhibit such propensities. Although many fluoroquinolones have been shown to display topoisomerase-independent antiproliferative effects against various human cancer cells, those that are significantly active against eukaryotic topoisomerase show the same DNA damaging properties as other topoisomerase poisons. Empirical models also show that fluoroquinolones mediate some unique immunomodulatory activities of suppressing pro-inflammatory cytokines and super-inducing interleukin-2. This article reviews the extended roles of fluoroquinolones and their prospects as lead for the unmet needs of "small and safe" multimodal-targeting drug scaffolds.

Immunobiological efficacy and immunotoxicity of novel synthetically prepared fluoroquinolone ethyl 6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylate

The present study examined the cytotoxicity, anti-cancer reactivity, and immunomodulatory properties of new synthetically prepared fluoroquinolone derivative 6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylate (6FN) in vitro. The cytotoxicity/toxicity studies (concentrations in the range 1-100μM) are focused on the cervical cancer cells HeLa, murine melanoma cancer cells B16, non-cancer fibroblast NIH-3T3 cells and reconstructed human epidermis tissues EpiDerm™. The significant growth inhibition of cancer cells HeLa and B16 was detected. The cytotoxicity was mediated via apoptosis-associated with activation of caspase-9 and -3. After 72h of treatment, the two highest 6FN concentrations (100 and 50μM) induced toxic effect on epidermis tissue EpiDerm™, even the structural changes in tissue were observed with concentration of 100μM. The effective induction of RAW 264.7 macrophages cell-release of pro- and anti-inflammatory T_H1, T_H2 and T_H17 cytokines, with anti-cancer and/or anti-infection activities, respectively, has been revealed even following low-dose exposition.

Topoisomerase Inhibitors: Fluoroquinolone Mechanisms of Action and Resistance

Quinolone antimicrobials are widely used in clinical medicine and are the only current class of agents that directly inhibit bacterial DNA synthesis. Quinolones dually target DNA gyrase and topoisomerase IV binding to specific domains and conformations so as to block DNA strand passage catalysis and stabilize DNA-enzyme complexes that block the DNA replication apparatus and generate double breaks in DNA that underlie their bactericidal activity. Resistance has emerged with clinical use of these agents and is common in some bacterial pathogens. Mechanisms of resistance include mutational alterations in drug target affinity and efflux pump expression and acquisition of resistance-conferring genes. Resistance mutations in one or both of the two drug target enzymes are commonly in a localized domain of the GyrA and ParC subunits of gyrase and topoisomerase IV, respectively, and reduce drug binding to the enzyme-DNA complex. Other resistance mutations occur in regulatory genes that control the expression of native efflux pumps localized in the bacterial membrane(s). These pumps have broad substrate profiles that include other antimicrobials as well as quinolones. Mutations of both types can accumulate with selection pressure and produce highly resistant strains. Resistance genes acquired on plasmids confer low-level resistance that promotes the selection of mutational high-level resistance. Plasmid-encoded resistance is because of Qnr proteins that protect the target enzymes from quinolone action, a mutant aminoglycoside-modifying enzyme that also modifies certain quinolones, and mobile efflux pumps. Plasmids with these mechanisms often encode additional antimicrobial resistances and can transfer multidrug resistance that includes quinolones.

The Current Case of Quinolones: Synthetic Approaches and Antibacterial Activity

Quinolones are broad-spectrum synthetic antibacterial drugs first obtained during the synthesis of chloroquine. Nalidixic acid, the prototype of quinolones, first became available for clinical consumption in 1962 and was used mainly for urinary tract infections caused by Escherichia coli and other pathogenic Gram-negative bacteria. Recently, significant work has been carried out to synthesize novel quinolone analogues with enhanced activity and potential usage for the treatment of different bacterial diseases. These novel analogues are made by substitution at different sites--the variation at the C-6 and C-8 positions gives more effective drugs. Substitution of a fluorine atom at the C-6 position produces fluroquinolones, which account for a large proportion of the quinolones in clinical use. Among others, substitution of piperazine or methylpiperazine, pyrrolidinyl and piperidinyl rings also yields effective analogues. A total of twenty six analogues are reported in this review. The targets of quinolones are two bacterial enzymes of the class II topoisomerase family, namely gyrase and topoisomerase IV. Quinolones increase the concentration of drug-enzyme-DNA cleavage complexes and convert them into cellular toxins; as a result they are bactericidal. High bioavailability, relative low toxicity and favorable pharmacokinetics have resulted in the clinical success of fluoroquinolones and quinolones. Due to these superior properties, quinolones have been extensively utilized and this increased usage has resulted in some quinolone-resistant bacterial strains. Bacteria become resistant to quinolones by three mechanisms: (1) mutation in the target site (gyrase and/or topoisomerase IV) of quinolones; (2) plasmid-mediated resistance; and (3) chromosome-mediated quinolone resistance. In plasmid-mediated resistance, the efflux of quinolones is increased along with a decrease in the interaction of the drug with gyrase (topoisomerase IV). In the case of chromosome-mediated quinolone resistance, there is a decrease in the influx of the drug into the cell.

Mechanisms of drug resistance: quinolone resistance

Quinolone antimicrobials are synthetic and widely used in clinical medicine. Resistance emerged with clinical use and became common in some bacterial pathogens. Mechanisms of resistance include two categories of mutation and acquisition of resistance-conferring genes. Resistance mutations in one or both of the two drug target enzymes, DNA gyrase and DNA topoisomerase IV, are commonly in a localized domain of the GyrA and ParE subunits of the respective enzymes and reduce drug binding to the enzyme-DNA complex. Other resistance mutations occur in regulatory genes that control the expression of native efflux pumps localized in the bacterial membrane(s). These pumps have broad substrate profiles that include quinolones as well as other antimicrobials, disinfectants, and dyes. Mutations of both types can accumulate with selection pressure and produce highly resistant strains. Resistance genes acquired on plasmids can confer low-level resistance that promotes the selection of mutational high-level resistance. Plasmid-encoded resistance is due to Qnr proteins that protect the target enzymes from quinolone action, one mutant aminoglycoside-modifying enzyme that also modifies certain quinolones, and mobile efflux pumps. Plasmids with these mechanisms often encode additional antimicrobial resistances and can transfer multidrug resistance that includes quinolones. Thus, the bacterial quinolone resistance armamentarium is large.

DNA binding, photo-induced DNA cleavage and cytotoxicity studies of lomefloxacin and its transition metal complexes

This work was focused on a study of the DNA binding and cleavage properties of lomefloxacin (LMF) and its ternary transition metal complexes with glycine. The nature of the binding interactions between compounds and calf thymus DNA (CT-DNA) was studied by electronic absorption spectra, fluorescence spectra and thermal denaturation experiments. The obtained results revealed that LMF and its complexes could interact with CT-DNA via partial/moderate intercalative mode. Furthermore, the DNA cleavage activities of the compounds were investigated by gel electrophoresis. Mechanistic studies of DNA cleavage suggest that singlet oxygen ((1)O2) is likely to be the cleaving agent via an oxidative pathway, except for Cu(II) complex which proceeds via both oxidative and hydrolytic pathways. Antimicrobial and antitumor activities of the compounds were also studied against some kinds of bacteria, fungi and human cell lines.

Fluoroquinolone antibiotics: an emerging class of environmental micropollutants

The aim of this review paper is to provide a comprehensive overview of different chemical and environmental aspects concerning fluoroquinolone antibiotics as emerging contaminants. A literature survey has been performed based on 204 papers from 1998 to mid-2013, resulting in a dataset consisting out of 4100 data points related to physical-chemical properties, environmental occurrence, removal efficiencies, and ecotoxicological data. In a first part, an overview is given on relevant physical-chemical parameters to better understand the behavior of fluoroquinolones during wastewater treatment and in the environment. Secondly, the route of these antibiotics after their application in both human and veterinary surroundings is discussed. Thirdly, the occurrence of fluoroquinolone residues is discussed for different environmental matrices. The final part of this review provides a tentative risk assessment of fluoroquinolone compounds and their transformation products in surface waters by means of hazard quotients. Overall, this review shows that fluoroquinolone antibiotics have a wide spread use and that their behavior during wastewater treatment is complex with an incomplete removal. As a result, it is observed that these biorecalcitrant compounds are present in different environmental matrices at potentially hazardous concentrations for the aquatic environment. The latter calls for actions on both the consumption as well as the wastewater treatment aspect to diminish the discharge of these biological active compounds.

Value of preapproval safety data in predicting postapproval hepatic safety and assessing the legitimacy of class warning

OBJECTIVE

The objective of this study was to systematically evaluate whether preapproval safety data for nonhepatotoxic drugs and hepatotoxic drugs can be compared to improve preapproval prediction of postapproval hepatic safety and to assess the legitimacy of applying class warnings.

METHODS

Drugs within a therapeutic class that included at least one drug that had been withdrawn from the market because of liver toxicity or had a warning of potential liver toxicity issued by major regulatory agencies, and at least one drug free from such regulatory action, were identified and divided into two groups: drugs with and drugs without regulatory action. Preapproval clinical data [including the elevation rates of alanine aminotransferse (ALT) and withdrawal due to liver toxicity, the number of patients with combined elevation of ALT and bilirubin, and liver failure] and nonclinical data (including chemical structures, metabolic pathways, and other significant findings in animal studies) were compared between the two groups.

RESULTS

Six drug classes were assessed in this study: thiazolidinediones, cyclooxygenase-2 inhibitors, fluoroquinolones, catechol-O-methyltransferase (COMT) inhibitors, leukotriene receptor inhibitors, and endothelin receptor antagonists. In two classes (COMT inhibitors and endothelin receptor antagonists), drugs with regulatory action had significantly higher rates of ALT elevation of more than threefold and greater numbers of patients with combined elevation of ALT and bilirubin than drugs without regulatory action. Drugs with regulatory action also had chemical structures or metabolic pathways associated with the toxicity. The legitimacy of class warnings was refuted in all six classes of drugs.

CONCLUSION

Preapproval safety data may help predict postapproval hepatic safety and can be used to assess the legitimacy of applying class warnings.

The effect of levofloxacin and moxifloxacin on cardiovascular functions of rats with streptozotocin-induced diabetes

Fluoroquinolone antibiotics cause rare, but clinically important, adverse events including hyperglycaemia and hypoglycaemia. The present study focuses on the possible effect of levofloxacin and moxifloxacin on the cardiovascular functions of rats with type I diabetes. Both antibiotics caused bradycardia. Levofloxacin but not moxifloxacin caused hypoglycaemia in diabetic rats and an increase in amplitude of the ST segment revealed by electrocardiogram (ECG) analysis of isolated hearts. In pressurized mesenteric arteries, levofloxacin did not affect the endothelium-derived hyperpolarising factor (EDHF) pathway or its main components, the small-conductance Ca(2+) activated potassium (SK(Ca)) and intermediate-conductance Ca(2+) activated potassium (IK(Ca)) channels. In moxifloxacin-treated rats, an increase in the EDHF response was observed, which was largely attributed to SK(Ca)-activation. In conclusion, levofloxacin and moxifloxacin use appeared to vary but with no evidence of impairment of the cardiovascular function. However, it is still possible that these antibiotics may produce different effects if there are co-morbidities and therefore their use must be with care.

Combined contributions of over-secreted glucagon-like peptide 1 and suppressed insulin secretion to hyperglycemia induced by gatifloxacin in rats

Accumulating evidences have showed that gatifloxacin causes dysglycemia in both diabetic and non-diabetic patients. Our preliminary study demonstrated that gatifloxacin stimulated glucagon-like peptide 1 (GLP-1) secretion from intestinal cells. The aim of the study was to investigate the association between gatifloxacin-stimulated GLP-1 release and dysglycemia in both normal and streptozotocin-induced diabetic rats and explore the possible mechanisms. Oral administration of gatifloxacin (100 mg/kg/day and 200 mg/kg/day) for 3 and 12 days led to marked elevation of GLP-1 levels, accompanied by significant decrease in insulin levels and increase in plasma glucose. Similar results were found in normal rats treated with 3-day gatifloxacin. Gatifloxacin-stimulated GLP-1 release was further confirmed in NCI-H716 cells, which was abolished by diazoxide, a K(ATP) channel opener. QT-PCR analysis showed that gatifloxacin also upregulated expression of proglucagon and prohormone convertase 3 mRNA. To clarify the contradiction on elevated GLP-1 without insulinotropic effect, effects of GLP-1 and gatifloxacin on insulin release were investigated using INS-1 cells. We found that short exposure (2h) to GLP-1 stimulated insulin secretion and biosynthesis, whereas long exposure (24 h and 48 h) to high level of GLP-1 inhibited insulin secretion and biosynthesis. Moreover, we also confirmed gatifloxacin acutely stimulated insulin secretion while chronically inhibited insulin biosynthesis. All the results gave an inference that gatifloxacin stimulated over-secretion of GLP-1, in turn, high levels of GLP-1 and gatifloxacin synergistically impaired insulin release, worsening hyperglycemia.

Cardiovascular and metabolic safety profiles of the fluoroquinolones

INTRODUCTION

Certain fluoroquinolones share similar indications of use. A comparison among Cardiovascular and metabolic (i.e., dysglycemia) safety profiles of the fluoroquinolones might be particularly useful for the prescribers' decision-making process as well as to hypothesize future researcher purposes.

AREAS COVERED

A literature search was conducted using keywords apt to identify information on safety profile of the fluoroquinolones. Publications concerned with descriptive and etiological surveys were manually reviewed.

EXPERT OPINION

Cardiac alterations and blood glucose impairments might be associated with any fluoroquinolone. However, the benefit/risk profile of these agents could be stratified for the single compounds. Several predisposing factors, such as diabetes, heart illnesses and their related pharmacotherapies, might exacerbate the risk of potentially serious adverse events. In this context, the opportunity of the more appropriate choice among different fluoroquinolones could be applicable.

Ciprofloxacin use in neonates: a systematic review of the literature

BACKGROUND

ciprofloxacin has no marketing authorization for use in neonates worldwide but it is prescribed for the treatment of neonatal life-threatening infections, mainly in developing countries and in Europe. Given the concerns about its toxicity in this population and the necessity for its use in specific clinical situations, we conducted a systematic review of the use of ciprofloxacin in neonates.

METHODS

we performed a systematic search of PubMed, Embase, and the Cochrane Database of Systematic Reviews and bibliographies of relevant articles. We included all studies, regardless of design, that reported efficacy, safety, and pharmacokinetics of ciprofloxacin for the treatment of any neonatal infectious condition. We excluded letters, editorials, preliminary reports, and abstracts.

RESULTS

observational cohort studies, case reports, and descriptions of patient series account for all literature reviewed. Ciprofloxacin was administrated in neonates as a salvage therapy for sepsis due to multidrug-resistant strains or with signs of clinical deterioration under first-line antibiotic treatment. Initial administration was always intravenous with variable dosing schedule. Clinical response to treatment was estimated at 64% and 91% in 2 cohort studies, with a median of 83% in case series. Of the 14 case reports, 12 yielded positive clinical outcomes. No serious adverse events, particularly joint toxicity, were observed, although evaluation was predominantly clinical and follow-up limited to few months after the end of treatment.

CONCLUSIONS

the current literature provides some information to support the use of ciprofloxacin in neonates. Additional high quality studies should be undertaken to provide reliable data on pharmacokinetics, efficacy, and long-term safety.

A man who wanted to commit suicide by hanging himself: an adverse effect of ciprofloxacin

In this case report, we describe a man who developed recurrent depression and suicidal ideation with a serious plan to commit suicide as definite adverse effect of ciprofloxacin, which had been prescribed for recurrent prostatitis.

Safety profile of the fluoroquinolones: analysis of adverse drug reactions in relation to prescription data using four regional pharmacovigilance databases in Italy

BACKGROUND

Fluoroquinolones are widely used both in primary care and in hospital settings. Since the last comparison performed in Italy on the safety profiles of different fluoroquinolones, a new molecule, prulifloxacin, has been introduced into the market and several warnings concerning this class of drugs have been released. The aim of this study was to reassess the safety profiles of fluoroquinolones using the database of the Italian Interregional Group of Pharmacovigilance (IGP) and the administrative data of fluoroquinolone prescriptions.

METHODS

All adverse drug reactions (ADRs) reported in four Italian regions (Lombardy, Veneto, Emilia Romagna and Tuscany) were retrieved from the IGP database. Consumption data (defined daily dose [DDD]/1000 inhabitants/day) were used as denominators. Both single reports and all ADRs (classified by System Organ Classes and MedDRA Preferred Term [PT]) due to fluoroquinolones were considered as numerators of each analysis, comparing two periods (2005 vs 2006). All fluoroquinolones with at least ten reports per year were included in the analysis.

RESULTS

On the basis of 272 reports (532 single ADRs or PTs), patients did not show any statistically significant differences between 2005 and 2006 in terms of sex, age and number of concurrent medications. After adjustment for drug consumption, moxifloxacin showed the highest reporting rate (84.6 reports/DDD/1000 inhabitants/day; 15.4 serious reports/DDD/1000 inhabitants/day) followed by prulifloxacin (72.2; 22.2 serious) and levofloxacin (55.3; 30.6 serious) in 2005. An increment of ADR/report rates was observed over the 2 years for all fluoroquinolones except prulifloxacin, which had the lowest ADR reporting rate in 2006 (25.0; 12.5 serious). In 2006, the rate of serious ADRs associated with prulifloxacin was lower than with ciprofloxacin, while in 2005 serious events were almost equal for both compounds (55.6 vs 47.6 serious ADRs/DDD/1000 inhabitants/day). Ciprofloxacin showed the highest proportion of cutaneous PTs (e.g. rash, exanthema). Tendinopathies were mainly due to levofloxacin.

CONCLUSIONS

These data suggest that different fluoroquinolones are characterized by different rates and types of ADRs. Among them, prulifloxacin was associated with more ADRs than other fluoroquinolones in 2005 but with fewer ADRs in 2006, when its consumption increased. Although these findings may represent an encouraging perspective towards a more appropriate use of fluoroquinolones because of their individual safety profiles, further pharmacoepidemiological studies must be performed to substantiate these results.

Safety profile of the fluoroquinolones: focus on levofloxacin

The fluoroquinolone class of antibacterial agents are among the most frequently prescribed drugs, with utility in a broad range of bacterial infections. Although very useful agents, the fluoroquinolones as a class are associated with a number of adverse events, some with considerable clinical significance. In the past 15-20 years, tolerability concerns have led to restrictions on the use of the fluoroquinolones and, in some instances, the withdrawal of agents from the market. This review focuses on the safety and tolerability of levofloxacin, a third-generation fluoroquinolone, relative to other fluoroquinolones. A literature search was performed of the MEDLINE database encompassing the dates 1980-2009, using as keywords the drug names levofloxacin and concurrently marketed fluoroquinolones combined with the words 'safety', 'adverse effect' or 'adverse drug reaction', or the name of the specific adverse effect. Adverse events commonly associated with the fluoroquinolones include gastrointestinal and CNS toxicity (most frequently headache and dizziness), as well as other adverse events including ECG abnormalities (for example QT interval prolongation), disrupted glucose metabolism, phototoxicity, tendon and joint disorders, hypersensitivity and skin disorders, and hepatic toxicity. Package inserts for the fluoroquinolones in Europe and the US contain warnings regarding these risks. US package inserts also carry 'black-box' warnings regarding the risk of tendon rupture and joint disorders with these agents; however, there is a substantial body of evidence to indicate that there are marked differences in the tolerability profiles of the individual agents within the fluoroquinolone class. These differences may be explained, at least in part, by structural differences: all fluoroquinolones share a basic quinolone core, with differences in specific side chains underlying the adverse event relationships. Furthermore, many of the fluoroquinolone-associated adverse effects and toxicities occur more frequently in patients with pre-existing risk factors, or in certain subpopulations. Notably, package inserts for the fluoroquinolones carry warnings regarding use in the elderly, paediatric patients and patients with pre-existing, or factors predisposing to, seizure disorders. Because of this, many adverse reactions with these agents could be prevented by improving patient screening and education. The recent withdrawal of gatifloxacin due to dysglycaemia makes it timely to review the safety and tolerability of the individual agents in this class. Overall, it appears that levofloxacin is relatively well tolerated, with low rates of clinically important adverse events such as CNS toxicity, cardiovascular toxicity and dysglycaemia.

The Utility of Fluoroquinolones in the Critically Ill

Fluoroquinolone antibiotics have been used for more than 40 years to treat a variety of infections from simple uncomplicated urinary tract infections to infections as severe as nosocomial-acquired pneumonia. Their availability both orally and intravenously, ease of dosing, favorable safety profile, and broad spectrum of activity have led to the pervasive use of these agents in both the community and institutions. Unfortunately, this widespread use has led to the development of resistance and subsequently, increased mortality. Resistance, specifically with Pseudomonas aeruginosa and Escherichia coli, as well as their association with the development of Clostridium difficile–associated diarrhea, has led many clinicians to question the use of fluoroquinolones in the critically ill. This article will review these issues related to the use of fluoroquinolones, in an effort to better define their role among institutionalized patients.

An overview of harms associated with beta-lactam antimicrobials: where do the carbapenems fit in?

The US Institute of Medicine's focus on patient safety has motivated hospital administrators to facilitate a culture of safety. As a result, subcommittees of the pharmacy and therapeutics committee have emerged in many hospitals to focus on adverse events and patient safety. Antimicrobial harms have gained the attention of practicing clinicians and hospital formulary committees, because they top the list of drugs that are associated with adverse events and because of certain serious harms that have ultimately led to the withdrawal of some antimicrobial agents. In the near future, several antimicrobials in the late phase of development will become available for clinical use (ceftobiprole, ceftaroline, and telavancin), and others (doripenem and dalbavancin) have recently joined the armamentarium. Because new antimicrobials will become part of the treatment armamentarium, it is important to discuss our current understanding of antimicrobial harms in general. Although not thought of as traditional adverse events, Clostridium difficile infection and development of resistance during therapy are adverse events that occur as a result of antimicrobial exposure and therefore are discussed. In addition, a distillation of our current understanding of β-lactam specific adverse events will be provided. Finally, new methods of administration are being evaluated that may influence peak concentration-related antimicrobial adverse events.

Ocular toxicity of fluoroquinolones

The ocular toxicity of fluoroquinolones and the risks of their use in the treatment of ocular infection were reviewed. Systematic identification, selection, review and synthesis of published English-language studies relating to fluoroquinolone use and safety in animals and humans was conducted. Although not free of complications, fluoroquinolones are generally safe when used to treat ocular infection. Ocular toxicity appears to be dose-dependent and results from class-effects and specific fluoroquinolone structures. Phototoxicity and neurotoxicity have been reported, and toxic effects on ocular collagen may be associated with Achilles tendinopathy. Corneal precipitation may provide an advantageous drug depot but delay healing and result in corneal perforation in approximately 10% of cases. Although human toxicity studies are limited, the current recommended dose for intracameral injection of ciprofloxacin is less than 25 microg. Intravitreal injections of ciprofloxacin 100 microg, ofloxacin 50 microg/mL, trovafloxacin 25 microg or less, moxifloxacin 160 microg/0.1 mL or less and pefloxacin 200 microg/0.1 mL are considered safe.

The safety profile of moxifloxacin and other fluoroquinolones in special patient populations

BACKGROUND

Fluoroquinolones, including ciprofloxacin, levofloxacin, gemifloxacin, and moxifloxacin, represent a major advance in the development of antimicrobial agents. They offer significant activity against Gram-negative pathogens, while more advanced generation fluoroquinolones including levofloxacin, gemifloxacin, and moxifloxacin are significantly active against Gram-positive (e.g., Streptococcus pneumoniae for some members of the class), typical, atypical, and anaerobic pathogens. Fluoroquinolones have a pharmacokinetic/pharmacodynamic profile that exhibits concentration-dependent killing and good oral absorption, allowing for once-daily dosing.

OBJECTIVE

Review of data from fluoroquinolone studies, with an emphasis on the associated rare, but potentially clinically important, adverse events in specific patient populations. Review of clinical efficacy is included where relevant to the topic under discussion.

METHODS

A literature search was conducted using terms including fluoroquinolones, moxifloxacin, ciprofloxacin, levofloxacin, gatifloxacin, gemifloxacin, safety, adverse events, drug interactions, and pharmacokinetic parameters to identify literature providing information regarding the safety profile of specified fluoroquinolones in special patient populations (i.e., the elderly, patients with liver disease, kidney disease, glycemic disorder, those at risk for cardiovascular events). Although specific date criteria were not applied to the search, preference was given to more recent publications. Online databases searched include MEDLINE and EMBASE and relevant textbooks were utilized as well.

FINDINGS

Fluoroquinolones, when used either as monotherapy or as combination therapy depending on their individual indications, attain adequate concentrations for treating infections in different target sites, including epithelial lining fluid, alveolar macrophages, skin, and gastrointestinal tissues. Overall, fluoroquinolones have predictable and mild-to-moderate adverse-event profiles and are generally well tolerated. Findings of this review are limited by the availability of publications and case reports.

CONCLUSIONS

Fluoroquinolones, are associated with rare, but clinically important, adverse events in special patient populations (including the elderly; those with hepatic, renal, or glycemic disorders; and those at risk for cardiovascular events). Recognition of differences in the clinical efficacy and safety profiles of fluoroquinolones in special patient populations should lead to better antimicrobial agent selection.

Retrospective analysis of electrocardiographic changes after administration of oral or intravenous garenoxacin in five phase I, placebo-controlled studies in healthy volunteers

BACKGROUND

Certain fluoroquinolones and macrolide antibiotics have been associated with prolongation of the corrected QT (QTc) interval or QT dispersion, leading to cardiac arrhythmias. Garenoxacin is a des-F(6)-quinolone with broad-spectrum antimicrobial activity and a favorable pharmacokinetic/pharmacodynamic profile. Its effects on electrocardiographic (ECG) parameters in healthy volunteers have not been reported.

OBJECTIVE

The cardiac safety profile of garenoxacin was further examined using data from healthy volunteers enrolled in 5 dose-ranging and comparative Phase I clinical studies.

METHODS

This was a retrospective analysis of 5 randomized, double-blind, placebo-controlled studies in which 224 healthy volunteers received oral or intravenous garenoxacin (50-1200 mg/d) for 1 to 28 days' dosing duration (<or=14 days' therapeutic duration). The effects of garenoxacin on the QT interval corrected using Bazett's formula (QTcB) and Fridericia's formula (QTcF) and the PR interval were assessed by counts of outliers, linear regressions, and exposure-response plots. Absence of a concentration-dependent effect of garenoxacin on changes from baseline ECG parameters was concluded if the 95% CI for the linear regression slopes of derived QTc- or PR-interval parameters relative to Cmax and C(avg0-12) (average garenoxacin plasma concentration from 0-12 hours after dosing) values for garenoxacin contained zero.

RESULTS

No clinically relevant changes in the QTc or PR intervals were observed over a range of garenoxacin plasma concentrations (Cmax: 0.5-38.6 microg/mL, oral dose range; 3.36-21.4 microg/mL, intravenous dose range). No volunteer had a prolongation from baseline that exceeded established thresholds for the QTcB or QTcF interval (>450 milliseconds for men, >470 milliseconds for women) or the PR interval (>250 milliseconds). One subject had a change in QTcB of 67 milliseconds 4 hours after administration of garenoxacin 400 mg PO on day 7, but the actual value was 418 milliseconds (baseline, 351 milliseconds); the corresponding change in QTcF was 49 milliseconds (actual, 408 milliseconds; baseline, 359 milliseconds). The means for other derived ECG parameters were generally similar between garenoxacin-treated volunteers and placebo controls.

CONCLUSION

In this retrospective analysis of data from healthy volunteers, garenoxacin had no clinically relevant dose-, route-of-administration-, or concentration-dependent effects on the QTc or PR interval across a dose range from 50 to 1200 mg/d.

Effects of acute renal failure and ganciclovir on the pharmacodynamics of levofloxacin-induced seizures in rats

Seizures have been reported in patients receiving fluoroquinolones, including levofloxacin (LVFX). In the present study, we investigated the effects of experimental renal failure and the concomitant treatment with ganciclovir on the pharmacodynamics of LVFX-induced seizures to identify whether these factors can alter the pharmacokinetics or the pharmacodynamics of LVFX. Male Wistar rats received an intravenous infusion of LVFX at 250, 500, or 1000 mg/h/rat until the onset of seizures, and samples of serum, brain, and cerebrospinal fluid (CSF) were obtained. The concentration of LVFX in CSF at the onset of seizures was not affected by the infusion rate, whereas that in serum and brain increased with increasing infusion rate. This suggests that the concentration of LVFX in CSF is an appropriate index of the drug concentration at the site of action. The concentration of LVFX in CSF at the onset of seizures was significantly lower in rats with renal failure than in the control rats. Pretreatment with methylguanidine, an uremic toxin, at 600 mg/h/rat for 8 min reduced the concentration of LVFX in CSF at the onset of seizures and the total body clearance of LVFX after the intravenous injection. In rats pretreated with ganciclovir at 500 mg/h/rat for 1 h, the concentration of LVFX in CSF at the onset of seizures was significantly lower than the control rats. These results suggest that renal failure and ganciclovir can be the risk factors for LVFX-induced seizures, and that they increase the sensitivity of the central nervous system to LVFX-induced seizures.

Effect of levofloxacin on serum glucose concentration in rats

To clarify the mechanism of fluoroquinolone-induced abnormalities in blood glucose, the effect of levofloxacin on serum glucose concentration was investigated in rats. Rats received an intravenous injection of levofloxacin and their arterial blood was sampled periodically. The serum glucose concentration decreased after an injection of 100 mg/kg of levofloxacin, while it increased at levofloxacin 300 mg/kg. The serum immunoreactive insulin concentration increased as the dose of levofloxacin increased. The serum epinephrine concentration was rapidly elevated by levofloxacin at 300 mg/kg. The serum histamine concentration increased after injections of levofloxacin, 200 and 300 mg/kg. Diphenhydramine (1 mg/kg) antagonized the hyperglycemia induced by 300 mg/kg of levofloxacin. In an in vitro study, the release of epinephrine from the adrenal medulla in the presence of levofloxacin was determined. Levofloxacin (300 microg/ml) did not affect epinephrine release from the adrenal medulla. Levofloxacin can induce hypoglycemia and hyperglycemia in rats. Levofloxacin can promote histamine release, leading to an increased serum epinephrine concentration and hyperglycemia.