Quinolones:

Identification of CH2-linked quinolone-aminopyrimidine hybrids as potent anti-MRSA agents: Low resistance potential and lack of cross-resistance with fluoroquinolone antibiotics

The structural optimization of B14, an antibacterial agent we previously obtained, has led to the discovery of a new class of CH2-linked quinolone-aminopyrimidine hybrids with potent anti-MRSA activities. Surprisingly, the hybrids lacking a C-6 fluoro atom at the quinolone nucleus showed equal or even stronger anti-MRSA activities than their corresponding 6-fluoro counterparts, despite the well-established structure-activity relationships (SARs) indicating that the 6-fluoro substituent enhances the antibacterial activity in conventional fluoroquinolone antibiotics. Moreover, these new hybrids, albeit structurally related to conventional fluoroquinolones, showed no cross-resistance with fluoroquinolone drugs. The most active compound, 15m, exhibited excellent activities with a MIC value of 0.39 μg/mL against both fluoroquinolone-sensitive strain USA500 and -resistant MRSA isolate Mu50. Further resistance development studies indicated MRSA is unlikely to acquire resistance against 15m. Moreover, 15m displayed favorable in vivo half-life and safety profiles. These findings suggest a rationale for further evolution of quinolone antibiotics with a high barrier to resistance.

Prevalence, Attributes, and Risk Factors of QT-Interval-Prolonging Drugs and Potential Drug-Drug Interactions in Cancer Patients: A Prospective Study in a Tertiary Care Hospital

Introduction Cancer chemotherapy regimens include multiple classes of adjuvant drugs as supportive therapy. Because of the concurrent intake of other drugs (like antiemetics, antidepressants, analgesics, and antimicrobials), there is a heightened risk for possible QT interval prolongation. There is a dearth of evidence in the literature regarding the usage of QT-prolonging anticancer drugs and associated risk factors that have the propensity to prolong QT interval. The purpose was to explore the extent of the use of QT-interval-prolonging drugs and potential QT-prolonging drug-drug interactions (QT-DDIs) in cancer patients attending OPD in a tertiary-care hospital. Methods This was a hospital-based, cross-sectional, observational study. Risk stratification of QT-prolonging drugs for torsades de pointes (TdP) was done by the Arizona Center for Education and Research on Therapeutics (AzCERT)/CredibleMeds-lists, and potential QT-DDIs were determined with four online DDI-checker-software. Results In 1331 cancer patients, the overall prevalence of potential QT-prolonging drug utilization was 97.3%. Ondansetron, pantoprazole, domperidone, and olanzapine were the most frequent QT-prolonging drugs in cancer patients. The top six antineoplastics with potential QT-prolonging and torsadogenic actions were capecitabine, oxaliplatin, imatinib, bortezomib, 5-fluorouracil, and bendamustine. Evidence-based pragmatic QTc interval prolongation risk assessment tools are imperative for cancer patients. Conclusion This study revealed a high prevalence of QT-prolonging drugs and QT-DDIs among cancer patients who are treated with anticancer and non-anticancer drugs. As a result, it's critical to take precautions, stay vigilant, and avoid QT-prolonging in clinical situations. Evidence-based pragmatic QTc interval prolongation risk assessment tools are needed for cancer patients.

Design and synthesis of novel desfluoroquinolone-aminopyrimidine hybrids as potent anti-MRSA agents with low hERG activity

Despite the fact that the introduction of a fluorine atom at the C-6 position has resulted in the evolution of fluoroquinolones, fluoroquinolone-induced cardiac toxicity has drawn considerable attention. In this context, desfluoroquinolone-based hybrids with involvement of C-7 aminopyrimidine functional group were designed and synthesized. The biological results showed majority of these hybrids still demonstrated potent anti-MRSA activity with MIC values between 0.38 and 1.5 μg/mL, despite the lack of the typical C-6 fluorine atom. Particularly, the most active B14 exhibited activities at submicromolar concentrations against a panel of MRSA strains including vancomycin-intermediate strains, levofloxacin-resistant isolates, and linezolid-resistant isolates, etc. As expected, it also displayed highly selective toxicity toward bacterial cells and low hERG inhibition. Further resistance development study indicated MRSA is unlikely to acquire resistance against B14. The docking study revealed that two hydrogen bonds were formed between the C-7 substituent and the surrounding DNA bases, which might contribute to overcome resistance by reducing the dependence on the magnesium-water bridge interactions with topoisomerase IV. These results indicate a promising strategy for developing new antibiotic quinolones to combat multidrug resistance and cardiotoxicity.

Responding to the challenge of untreatable gonorrhea: ETX0914, a first-in-class agent with a distinct mechanism-of-action against bacterial Type II topoisomerases

With the diminishing effectiveness of current antibacterial therapies, it is critically important to discover agents that operate by a mechanism that circumvents existing resistance. ETX0914, the first of a new class of antibacterial agent targeted for the treatment of gonorrhea, operates by a novel mode-of-inhibition against bacterial type II topoisomerases. Incorporating an oxazolidinone on the scaffold mitigated toxicological issues often seen with topoisomerase inhibitors. Organisms resistant to other topoisomerase inhibitors were not cross-resistant with ETX0914 nor were spontaneous resistant mutants to ETX0914 cross-resistant with other topoisomerase inhibitor classes, including the widely used fluoroquinolone class. Preclinical evaluation of ETX0914 pharmacokinetics and pharmacodynamics showed distribution into vascular tissues and efficacy in a murine Staphylococcus aureus infection model that served as a surrogate for predicting efficacious exposures for the treatment of Neisseria gonorrhoeae infections. A wide safety margin to the efficacious exposure in toxicological evaluations supported progression to Phase 1. Dosing ETX0914 in human volunteers showed sufficient exposure and minimal adverse effects to expect a highly efficacious anti-gonorrhea therapy.

Torsades de pointes induced by garenoxacin in association with pacing failure in an elderly woman with VDD pacemaker

An 86-year-old woman was admitted to the hospital for syncope and convulsion 4 days after starting antibiotic therapy for pneumonia with oral garenoxacin 400 mg/day. She had a VDD pacemaker for complete atrioventricular (AV) block. Her electrocardiogram showed marked QT prolongation and during pacemaker interrogation pacing failure probably due to battery depletion induced torsades de pointes. After cessation of garenoxacin, QTc returned to normal range subsequently and a new pacemaker was implanted. In patients with risks of QT prolongation, garenoxacin should be used cautiously with QT interval monitoring.

Medication-related complications in the trauma patient

Trauma patients are twice as likely to have adverse reactions to medication as nontrauma patients. The need for medication in trauma patients is high. Surgery is often necessary, and immunosuppression and hypercoagulability may be present. Adverse drug events can be caused in part by altered pharmacokinetics, drug interactions, and polypharmacy. Medications may also have serious long-term adverse effects, which must be considered. It is not the purpose of this review article to discuss all adverse effects of all medications. This article will discuss the more common adverse effects of medications for trauma patients in the acute care setting, in the following categories: pain control, sedation, antibiotics, seizure prophylaxis in head trauma, atrial fibrillation, deep vein thrombosis and pulmonary embolism prophylaxis, hemodynamic support, adrenal insufficiency, factor VIIa.

Proarrhythmic potential of antimicrobial agents

Several antiarrhythmic and non-cardiovascular drug therapies including antimicrobial agents have been implicated as the causes for QT interval prolongation, torsades de pointes (TdP) ventricular tachycardia and sudden cardiac death. Most of the drugs that have been associated with the lengthening of the QT interval or development of TdP can also block the rapidly activating component of the delayed rectifier potassium current (IKr) in the ventricular cardiomyocytes. This article presents a review of the current literature on the QT interval prolonging effect of antimicrobials based on the results of the in vitro, in vivo studies and case reports. Our observations were derived from currently available Medline database. As we found, the most frequently QT interval prolonging antimicrobials are erythromycin, clarithromycin, fluoroquinolones, halofantrine, and pentamidine. Almost every antimicrobial-associated QT interval prolongation occurs in patients with multiple risk factors of the following: drug interactions, female gender, advanced age, structural heart disease, genetic predisposition, and electrolyte abnormalities. In conclusion, physicians should avoid prescribing antimicrobials having QT prolonging potential for patients with multiple risk factors. Recognition and appropriate treatment of TdP are also indispensable.

Ciprofloxacin-induced Q-T interval prolongation

PURPOSE

A case of Q-T interval prolongation in a pediatric patient with no known risk factors for the development of a long Q-T syndrome is reported.

SUMMARY

A 16-year-old boy arrived at a children's hospital reporting mucous diarrhea that had lasted two weeks, light-headedness with two blackouts on the day before his arrival to the hospital, and a 4.3-kg weight loss over the previous three weeks. He had a 3.5-year history of Crohn's disease and had been hospitalized for two months with a diagnosis of colitis with cryptitis. He was admitted for the treatment of an acute flare of Crohn's disease and a perirectal abscess. The patient was started on i.v. ciprofloxacin 400 mg twice daily and metronidazole 500 mg every six hours. The selected agents provided adequate empirical coverage of the suspected organisms and would not be contraindicated with the patient's allergy to penicillin. Within 48 hours of administration of ciprofloxacin, the patient became bradycardic. The cardiology service was consulted, and an electrocardiogram showed a mildly prolonged Q-T interval (corrected Q-T interval, 486 msec) and low heart rate (42 beats/min). Antimicrobial therapy was changed to ampicillin and then to linezolid. The patient's Q-T interval normalized within seven days of ciprofloxacin discontinuation. The patient had no further cardiac anomalies. Two weeks later, he was discharged on linezolid and aztreonam for the treatment of his abscess and was responding to treatment.

CONCLUSION

A pediatric patient with Crohn's disease and colitis with cryptitis developed a prolonged Q-T interval within 48 hours of treatment with ciprofloxacin.

QT Interval prolongation and torsades de pointes due to a coadministration of ciprofloxacin and azimilide in a patient with implantable cardioverter-defibrillator

The presented case report describes a male patient with an implanted cardioverter-defibrillator (ICD) in whom a coadministration of ciprofloxacin and azimilide caused QT interval prolongation and multiple episodes of torsades de pointes (TdP) followed by ICD shocks (arrhythmic storm). The case highlights a not described drug interaction between azimilide and ciprofloxacin, which is believed to be the safest member of fluoroquinolones class.

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.

Arrhythmias associated with fluoroquinolone therapy

Fluoroquinolones are widely used and well tolerated antibacterial agents. However, prolongation of the QT interval is an adverse effect associated with the use of fluoroquinolones. According to the available case reports and clinical studies, moxifloxacin carries the greatest risk of QT prolongation from all available quinolones in clinical practice and it should be used with caution in patients with predisposing factors for Torsades de pointes (Tdp). Although gemifloxacin, levofloxacin and ofloxacin are associated with a lower risk of QT prolongation compared with moxifloxacin, they should also be used with caution in patients with risk factors for QT prolongation. Ciprofloxacin appears to be associated with the lowest risk for QT prolongation and the lowest rate of Tdp. The overall risk of Tdp is small with the use of fluoroquinolones. Clinicians can minimise that risk by avoiding prescriptions of multiple medications associated with QT interval prolongation, especially in high-risk patients.

Drug-induced QT interval prolongation after ciprofloxacin administration in a patient receiving olanzapine

Several non-antiarrhythmic drugs including antibiotic and antipsychotic agents have been shown to prolong cardiac repolarization predisposing to torsade de pointes ventricular tachycardia. Blockade of the delayed rectifier (repolarising) potassium current and drug interactions with inhibitors of the CYP-mediated metabolism are the most common underlying mechanisms. In the present case report, an elderly woman receiving a long-term medication with azathioprine, olanzapine and valsartan developed a marked QT interval prolongation after intravenous administration of ciprofloxacin.

Effect of ciprofloxacin and levofloxacin on the QT interval: is this a significant "clinical" event?

BACKGROUND

The widespread use of the fluoroquinolones has raised the question of the cardiac safety of these medications. This widespread use of this class of antibiotics has displayed their safety profile, which is actually more favorable than many other drug classes. The cardiac toxicity issue at the center of this discussion is the prolongation of the QT interval leading to torsade de pointes. Ciprofloxacin and levofloxacin, two of the more commonly used fluoroquinolones, are considered less likely than other fluoroquinolones to prolong the QT interval. The authors set out to evaluate the effect on the QT interval of patients after administration of ciprofloxacin and levofloxacin.

METHODS

A prospective evaluation of 38 consecutive patients evaluated by the infectious disease service and receiving either ciprofloxacin or levofloxacin was undertaken. Twelve-lead electrocardiograms were obtained at baseline and at least 48 hours after the first dose of the antibiotic was administered. Both the longest QT interval and the mean QT interval were evaluated. To account for variations in heart rate, the corrected QT interval was calculated by using Bazett's formula (QTc = QT(square root of) R-R). Statistical analysis was undertaken to assess for the presence of a change after the administration of the antibiotic.

RESULTS

Thirty-eight patients (mean age, 65 +/- 19 years), 23 women and 15 men, were studied. There was a small but significant increase in the longest QTc intervals over baseline in patients receiving levofloxacin; there was no significant change in the mean QTc interval. However, one patient who received levofloxacin was, statistically, an outlier and, on retrospective analysis, had demonstrated severe electrolyte disturbances at the time of the study. When this patient was excluded, the increase in the longest QTc interval was not significant. Patients receiving ciprofloxacin did not demonstrate any significant change in the longest QTc interval or mean QTc interval.

CONCLUSIONS

Neither levofloxacin nor ciprofloxacin significantly prolonged the mean QTc interval over baseline. When electrolyte deficiencies in one of the patients evaluated were taken into account, this also held true for the longest QTc interval. There is, therefore, evidence that taking ciprofloxacin or levofloxacin, assuming that there are not any concurrent risk factors, will not cause a significant prolongation in the QT interval.

Ciprofloxacin-induced acquired long QT syndrome

Quinolone antibiotics have potentially serious proarrhythmic effects. The effects on intracardiac potassium channels result in QT interval prolongation, leading to torsades de pointes. Evidence suggests fluoroquinolones cause QT-mediated proarrhythmia, and weak evidence links ciprofloxacin with QT-mediated arrhythmias. Ciprofloxacin may be given to select patients because the agent is believed to be safer than other drugs in its class. We report two cases of unexplained cardiac arrest temporally related to ciprofloxacin administration. Two female patients (ages 44 and 67 years) developed marked QTc prolongation (QTc 590 and 680 ms) within 24 hours of ciprofloxacin administration, with recurrent syncope and documented torsades de pointes requiring defibrillation. The patients previously were stable with sotalol and amiodarone therapy for supraventricular arrhythmia without obvious QTc prolongation prior to ciprofloxacin therapy. Marked QTc prolongation and subsequent proarrhythmia became a clinical concern only after initiation of ciprofloxacin. In both cases, the QTc normalized after cessation of ciprofloxacin. Ciprofloxacin may cause QTc prolongation and rarely torsades de pointes. This effect is of particular concern in patients with predisposing factors, such as concomitant medications or underlying heart disease reflecting decreased repolarization reserve.