Prevalence of and risk factors for dysglycemia in patients receiving gatifloxacin and levofloxacin in an outpatient setting

Risk for hypoglycemic emergency with levofloxacin use, a population-based propensity score matched nested case-control study

Potential association between oral levofloxacin use and hypoglycemic emergency (HE) have been established. However, a large epidemiological study is required to verify this observation. This study aimed to determine if use of oral levofloxacin increased the risk of HE. The nationwide database between 1999 and 2013, including 1.6 million patients with type 2 diabetes (T2D), was used to conduct a nested case-control study. Cases and controls comprised of patients with and without HE, respectively. To avoid indication bias the control subjects were chosen through propensity score matching with cases in a 10-fold ratio. T2D severity was classified based on the adjusted diabetic complication severity index score. 26,695 and 266,950 matched patients with T2D, were finally used as cases and controls, respectively, for the analysis. Multivariate logistic regression analysis showed that antibiotic use was associated with an increased risk for HE (adjusted odds ratio (aOR) = 6.08, 95% confidence interval (95% CI): 5.79–6.38). When compared with antibiotic non-users, those who used fluoroquinolones and sulfonamides displayed the highest (aOR = 12.05, 95% CI: 10.66–13.61) and second highest (aOR = 7.20, 95% CI: 6.29–8.24) risks of HE, respectively. The associated risk for HE was significantly higher with levofloxacin than that with cephalosporins (aOR = 5.13, 95% CI: 2.28–11.52) and penicillin (aOR = 9.40, 95% CI: 2.25–39.24). In the joint effect analyses, the risk for HE increased with the combination of levofloxacin with insulin (aOR = 8.42, 95% CI: 1.91–37.00) or sulfonylurea (aOR = 3.56, 95% CI: 1.12–11.33). Use of oral levofloxacin, compared to that of other antibiotics, was found to be significantly associated with HE in T2D patients. Clinicians should exercise caution while prescribing levofloxacin, especially when combined with insulin or sulfonylurea.

How Safe are Fluoroquinolones for Diabetic Patients? A Systematic Review of Dysglycemic and Neuropathic Effects of Fluoroquinolones

Introduction

The US Food and Drug Administration issued safety warnings about neuropathy in 2013 and dysglycemia in 2018 caused by fluoroquinolone use, mainly based on case reports and case series. We conducted this systematic review to evaluate the safety of fluoroquinolones in diabetic patients by investigating their dysglycemic and neuropathic effects.

Methods

PubMed, Scopus, and Google Scholar were searched for randomized controlled trials and observational studies published from inception till September 2019 evaluating the safety of fluoroquinolones. Efficacy studies of fluoroquinolones reporting these adverse effects were also included. Primary outcomes were hypoglycemia, hyperglycemia, and neuropathy among patients with or without diabetes and treated with fluoroquinolones compared with placebo or other antibiotics. The Cochrane Collaboration tool for randomized controlled trials and modified Newcastle-Ottawa quality-assessment scale were used for assessment of the included studies.

Results and Discussion

A total of 725 studies were identified in the initial search. After screening of titles and abstracts and full-text review, 16 articles fulfilled the inclusion criteria. The sampled patients were aged 30-78 years. Hyperglycemia was reported in 1,588 patients that received fluoroquinolone among eight studies with 4,663 patients, and hypoglycemia was reported in 2,179 patients that received fluoroquinolones among eleven studies with 6,208 patients. Dysglycemia was not generally associated with diabetes mellitus per se. Nevertheless, patients with more comorbidities, especially those with chronic kidney disease, receiving antidiabetics and/or steroids had more glycemic events when treated with fluoroquinolones.

Conclusion

Moxifloxacin was found to be associated the most and ciprofloxacin the least with dysglycemia. fluoroquinolones must be used with great caution among diabetic patients who have comorbidities and are receiving antidiabetics and/or steroids. Further evidence is required from studies on neuropathy caused by fluoroquinolones.

Fatal hypoglycemia with ciprofloxacin in a dialysis patient: A case report

In patients with renal dysfunction, it is important to avoid prescribing fluoroquinolones including ciprofloxacin.

Successful Use of Octreotide Therapy for Refractory Levofloxacin-Induced Hypoglycemia: A Case Report and Literature Review

Fluoroquinolones are commonly prescribed antimicrobials that have been implicated in alterations of glucose metabolism. We report a case of refractory fluoroquinolone-induced hypoglycemia in a patient with type-2 diabetes mellitus on glipizide that was successfully treated with octreotide. A patient was admitted with hypoglycemia after having been initiated on levofloxacin therapy. Despite treating the hypoglycemia supportively with multiple boluses of 25 g of dextrose, a continuous dextrose infusion, and glucagon, the patient experienced repeated episodes of rebound hypoglycemia. The persistent hypoglycemia was eventually reversed with the administration of subcutaneous octreotide. Clinicians should be cognizant of this adverse effect of fluoroquinolones, as well as predisposing risk factors, and consider octreotide as an adjunctive therapy for refractory hypoglycemia cases.

Safety of Delafloxacin: Focus on Adverse Events of Special Interest

Background

Fluoroquinolones have been widely used for a variety of Gram-positive and Gram-negative infections, and by 2002 they had become the most commonly prescribed class of antibiotics for adults in the United States. With widespread use, the class has become associated with a range of adverse events. Delafloxacin is a fluoroquinolone approved in the United States for the treatment of adults with acute bacterial skin and skin structure infections (ABSSSIs). Delafloxacin is differentiated from other fluoroquinolones due to structural differences and in its activity against methicillin-resistant Staphylococcus aureus, including quinolone-resistant strains. This paper reviews the safety profile of delafloxacin across clinical studies with an emphasis on the incidence of adverse events of special interest that are associated with fluoroquinolones.

Methods

Data from 2 completed phase III studies of delafloxacin for the treatment of ABSSSIs were pooled and are the primary focus of this paper. Additional support from the full safety analysis set (30 completed phase I to phase III clinical studies) is included where applicable.

Results

Fewer patients in the pooled delafloxacin group had AESIs than in the comparator group (7.0% vs 9.2%, respectively). Delafloxacin had a low rate of discontinuations due to treatment-related adverse events (<1%). Serious adverse events occurred at similar rates in patients treated with delafloxacin vs comparators.

Conclusions

Serious adverse events occurred at similar rates in patients treated with delafloxacin vs nonquinolone comparators used to treat ABSSSIs.

Clinicaltrials.gov identifier

NCT01984684 and NCT01811732

Hypoglycemia after antimicrobial drug prescription for older patients using sulfonylureas

IMPORTANCE

Certain antimicrobial drugs interact with sulfonylureas to increase the risk of hypoglycemia.

OBJECTIVE

To determine the risk of hypoglycemia and associated costs in older patients prescribed glipizide or glyburide who fill a prescription for an antimicrobial drug.

DESIGN, SETTING, AND PARTICIPANTS

This was a retrospective cohort study of Texas Medicare claims from 2006 to 2009 for patients 66 years or older who were prescribed glipizide or glyburide and who also filled a prescription for 1 of the 16 antimicrobials most commonly prescribed for this population.

METHODS

We assessed hypoglycemia events and associated Medicare costs in patients prescribed 1 of 7 antimicrobial agents thought to interact with sulfonylureas, using noninteracting antimicrobials as a comparison. We used a repeated measure logistic regression, controlling for age, sex, ethnicity, Medicaid eligibility, comorbidity, prior emergency department visits for hypoglycemia, prior hospitalizations for any cause, nursing home residence, and indication for the antimicrobial. We estimated odds of hypoglycemia, number needed to harm, deaths during hospitalization for hypoglycemia, and Medicare costs for hypoglycemia treatment.

MAIN OUTCOMES AND MEASURES

Any hospitalization or emergency department visit owing to hypoglycemia within 14 days of antimicrobial exposure.

RESULTS

In multivariable analyses controlling for patient characteristics and indication for antimicrobial drug use, clarithromycin (odds ratio [OR], 3.96 [95% CI, 2.42-6.49]), levofloxacin (OR, 2.60 [95% CI, 2.18-3.10]), sulfamethoxazole-trimethoprim (OR, 2.56 [95% CI, 2.12-3.10]), metronidazole (OR, 2.11 [95% CI, 1.28-3.47]), and ciprofloxacin (OR, 1.62 [95% CI, 1.33-1.97]) were associated with higher rates of hypoglycemia compared with a panel of noninteracting antimicrobials. The number needed to harm ranged from 71 for clarithromycin to 334 for ciprofloxacin. Patient factors associated with hypoglycemia included older age, female sex, black or Hispanic race/ethnicity, higher comorbidity, and prior hypoglycemic episode. In 2009, 28.3% of patients prescribed a sulfonylurea filled a prescription for 1 of these 5 antimicrobials, which were associated with 13.2% of all hypoglycemia events in patients taking sulfonylureas. The treatment of subsequent hypoglycemia adds $30.54 in additional Medicare costs to each prescription of 1 of those 5 antimicrobials given to patients taking sulfonylureas.

CONCLUSIONS AND RELEVANCE

Prescription of interacting antimicrobial drugs to patients on sulfonylureas is very common, and is associated with substantial morbidity and increased costs.

Effect of fluoroquinolones on mitochondrial function in pancreatic beta cells

Hyper- and hypoglycaemias are known side effects of fluoroquinolone antibiotics, resulting in a number of fatalities. Fluoroquinolone-induced hypoglycaemias are due to stimulated insulin release by the inhibition of the KATP channel activity of the beta cell. Recently, it was found that fluoroquinolones were much less effective on metabolically intact beta cells than on open cell preparations. Thus the intracellular effects of gatifloxacin, moxifloxacin and ciprofloxacin were investigated by measuring NAD(P)H- and FAD-autofluorescence, the mitochondrial membrane potential, and the adenine nucleotide content of isolated pancreatic islets and beta cells. 100 μM of moxifloxacin abolished the NAD(P)H increase elicited by 20mM glucose, while gatifloxacin diminished it and ciprofloxacin had no significant effect. This pattern was also seen with islets from SUR1 Ko mice, which have no functional KATP channels. Moxifloxacin also diminished the glucose-induced decrease of FAD-fluorescence, which reflects the intramitochondrial production of reducing equivalents. Moxifloxacin, but not ciprofloxacin or gatifloxacin significantly reduced the effect of 20mM glucose on the ATP/ADP ratio. The mitochondrial hyperpolarization caused by 20mM glucose was partially antagonized by moxifloxacin, but not by ciprofloxacin or gatifloxacin. Ultrastructural analyses after 20 h tissue culture showed that all three compounds (at 10 and 100 μM) diminished the number of insulin secretory granules and that gatifloxacin and ciprofloxacin, but not moxifloxacin induced fission/fusion configurations of the beta cell mitochondria. In conclusion, fluoroquinolones affect the function of the mitochondria in pancreatic beta cells which may diminish the insulinotropic effect of KATP channel closure and contribute to the hyperglycaemic episodes.

Risk of severe dysglycemia among diabetic patients receiving levofloxacin, ciprofloxacin, or moxifloxacin in Taiwan

BACKGROUND

Observational studies and fatal case reports raise concern about the safety of severe dysglycemia associated with fluoroquinolone use. The objective of this study was to assess the risk of severe dysglycemia among diabetic patients who received different fluoroquinolones.

METHODS

In a population-based inception cohort study of diabetic patients covering the period from January 2006 to November 2007, outpatient new users of levofloxacin, ciprofloxacin, moxifloxacin, cephalosporins, and macrolides orally were identified. Study events were defined as emergency department visits or hospitalization for dysglycemia within 30 days following the initiation of antibiotic therapy. Results were analyzed with adjusted multinomial propensity score.

RESULTS

A total of 78 433 diabetic patients receiving the antibiotics of interest were included in the study. The absolute risk of hyperglycemia per 1000 persons was 6.9 for moxifloxacin and 1.6 for macrolides. In contrast, the risk of hypoglycemia was 10.0 for moxifloxacin and 3.7 for macrolides. The adjusted odds ratios (AORs) and 95% confidence intervals (CIs) of levofloxacin, ciprofloxacin, and moxifloxacin compared with macrolides were 1.75 (1.12-2.73), 1.87 (1.20-2.93), and 2.48 (1.50-4.12), respectively, for hyperglycemia and 1.79 (1.33-2.42), 1.46 (1.07-2.00), and 2.13 (1.44-3.14), respectively, for hypoglycemia. Patients taking moxifloxacin faced a significantly higher risk of hypoglycemia than those receiving ciprofloxacin. A significant increase in the risk of hypoglycemia was also observed among patients receiving moxifloxacin concomitantly with insulin (AOR, 2.28; 95% CI, 1.22-4.24).

CONCLUSIONS

Diabetics using oral fluoroquinolones faced greater risk of severe dysglycemia. The risk of hypoglycemia varied according to the type of fluoroquinolone administered, and was most commonly associated with moxifloxacin.

Evaluation of initial and steady-state gatifloxacin pharmacokinetics and dose in pulmonary tuberculosis patients by using monte carlo simulations

A 4-month regimen of gatifloxacin with rifampin, isoniazid, and pyrazinamide is being evaluated for the treatment of tuberculosis in a phase 3 randomized controlled trial (OFLOTUB). A prior single-dose study found that gatifloxacin exposure increased by 14% in the combination. The aims of the study are to evaluate the initial and steady-state pharmacokinetics of gatifloxacin when daily doses are given to patients with newly diagnosed drug-sensitive pulmonary tuberculosis as part of a combination regimen and to evaluate the gatifloxacin dose with respect to the probability of attaining a pharmacokinetic/pharmacodynamic target. We describe the population pharmacokinetics of gatifloxacin from the first dose to a median of 28 days in 169 adults enrolled in the OFLOTUB trial in Benin, Guinea, Senegal, and South Africa. The probability of achieving a ratio of ≥125 for the area under the concentration time curve to infinity (AUC0-∞) for the free fraction of gatifloxacin over the MIC (fAUC/MIC) was investigated using Monte Carlo simulations. The median AUC0-∞ of 41.2 μg · h/ml decreased on average by 14.3% (90% confidence interval [CI], -90.5% to +61.5%) following multiple 400-mg daily doses. At steady state, 90% of patients achieved an fAUC/MIC of ≥125 only when the MIC was <0.125 μg/ml. We conclude that systemic exposure to gatifloxacin declines with repeated daily 400-mg doses when used together with rifampin, isoniazid, and pyrazinamide, thus compensating for any initial increase in gatifloxacin levels due to a drug interaction. (The OFLOTUB study has been registered at ClinicalTrials.gov under registration no. NCT00216385.).

Potentially harmful drug-drug interactions in the elderly: a review

BACKGROUND

Elderly patients are vulnerable to drug interactions because of age-related physiologic changes, an increased risk for disease associated with aging, and the consequent increase in medication use.

OBJECTIVE

The purpose of this narrative review was to describe findings from rigorously designed observational cohort and case-control studies that have assessed specific drug interactions in elderly patients.

METHODS

The PubMed and International Pharmaceutical Abstracts databases were searched for studies published in English over the past 10 years (December 2000-December 2010) using relevant Medical Subject Headings terms (aged; aged, 80 and over; and drug interactions) and search terms (drug interaction and elderly). Search strategies were saved and repeated through September 2011 to ensure that the most recent relevant published articles were identified. Additional articles were found using a search of review articles and reference lists of the identified studies. Studies were included if they were observational cohort or case-control studies that reported specific adverse drug interactions, included patients aged ≥65 years, and evaluated clinically meaningful end points. Studies were excluded if they used less rigorous observational designs, assessed pharmacokinetic/pharmacodynamic properties, evaluated drug-nutrient or drug-disease interactions or interactions of drug combinations used for therapeutic benefit (eg, dual antiplatelet therapy), or had inconclusive evidence.

RESULTS

Seventeen studies met the inclusion criteria. Sixteen studies reported an elevated risk for hospitalization in older adults associated with adverse drug interactions. The drug interactions included: angiotensin-converting enzyme (ACE) inhibitors and potassium-sparing diuretics, ACE inhibitors or angiotensin receptor blockers and sulfamethoxazole/trimethoprim, benzodiazepines or zolpidem and interacting medications, calcium channel blockers and macrolide antibiotics, digoxin and macrolide antibiotics, lithium and loop diuretics or ACE inhibitors, phenytoin and sulfamethoxazole/trimethoprim, sulfonylureas and antimicrobial agents, theophylline and ciprofloxacin, and warfarin and antimicrobial agents or nonsteroidal anti-inflammatory drugs. One study reported the risk for breast cancer-related death as a function of paroxetine exposure among women treated with tamoxifen.

CONCLUSIONS

Several population-based studies have reported significant harm associated drug interactions in elderly patients. Increased awareness and interventions aimed at reducing exposure and minimizing the risks associated with potentially harmful drug combinations are needed.

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.

Effect of enoxacin, felbinac, and sparfloxacin on fatty acid metabolism and glucose concentrations in rat tissues

Multiple changes in metabolic levels could be useful for understanding physiological toxicity. To explore further risk factors for the convulsions induced by the interaction of nonsteroidal anti-inflammatory and new quinolone antimicrobial drugs, the effect of sparfloxacin, enoxacin, and felbinac on fatty acid metabolism and glucose concentrations in the liver, brain, and blood of rats was investigated. The levels of long-chain acyl-CoAs (C(18:1) and C(20:4)) in the liver and brain were decreased at the onset of convulsions induced by the coadministration of enoxacin with felbinac. Then, glucose concentrations in the liver and blood were decreased, whereas they were increased in a dose-dependant manner in the brain. However, the formation of acyl-CoAs and glucose levels in the liver, brain, and blood was not significantly influenced by enoxacin, felbinac, and sparfloxacin alone, respectively. The disturbance of both fatty acid metabolism and glucose levels might be associated with the increased susceptibility to convulsions, which may contribute to further understanding of the toxic effects associated with these drugs.

Glimepiride-Induced Hypoglycemia with Ciprofloxacin, Metronidazole, and Acute Kidney Injury

A 79-year-old white male presented to the emergency room with altered mental status and a blood glucose of 28 mg/dL. He was taking glimepiride 1 mg by mouth daily prior to admission and had recently been prescribed ciprofloxacin and metronidazole for diverticulitis. The patient was also found to have acute-on-chronic renal failure upon presentation. Escalated dextrose infusion with repeated doses of D50W and glucagon failed to sustain his blood glucose, which remained in the range of 30 to 50 mg/dL. Salvage treatment with intravenous octreotide was implemented successfully; only one dose of D50W was required after octreotide initiation and blood glucose normalized within several hours. In the presence of this patient's complex medication therapy, we explore the contributing causes of hypoglycemia. Fluoroquinolones are widely associated with dysglycemias, particularly in diabetic patients receiving hypoglycemic agents. Similarly, renal insufficiency has been implicated to precipitate hypoglycemia with sulfonylureas, with dosage adjustment being required almost class-wide. We also recognize a theoretical drug interaction mediated by metronidazole-induced CYP 2C9 inhibition of glimepiride metabolism. Sulfonylurea-induced hypoglycemia can be serious and refractory to traditional therapy and can be exacerbated by multiple factors, such as drug interactions or impaired renal function. In the era of complex medication therapy for patient populations with multiple disease states, we present a severe episode of glimepiride-induced hypoglycemia with multiple causative factors.

Anti-infectives and the risk of severe hypoglycemia in users of glipizide or glyburide

The objective of this study was to evaluate whether orally administered anti-infectives increase the risk of severe hypoglycemia in users of glipizide or glyburide. We performed two case-control studies and two case-crossover studies using US Medicaid data. All the anti-infectives examined were associated with an elevated risk of severe hypoglycemia. Using cephalexin as the reference category, in glipizide users, statistically significant associations were found with co-trimoxazole (odds ratio (OR) = 3.14; 95% confidence interval (CI): 1.83-5.37); clarithromycin (OR = 2.90; 95% CI: 1.69-4.98); fluconazole (OR = 2.53; 95% CI: 1.23-5.23); and levofloxacin (OR = 2.09; 95% CI: 1.35-3.25). In glyburide users, with cephalexin as the reference, statistically significant associations were found with clarithromycin (OR = 5.02; 95% CI: 3.35-7.54); levofloxacin (OR = 2.83; 95% CI: 1.73-4.62); co-trimoxazole (OR = 2.68; 95% CI: 1.59-4.52); fluconazole (OR = 2.20; 95% CI: 1.04-4.68); and ciprofloxacin (OR = 2.08; 95% CI: 1.23-3.52). In conclusion, exposure to all studied anti-infective agents were associated with subsequent severe hypoglycemia. Using cephalexin as the reference, drug-drug interactions were evident with ciprofloxacin (in glyburide users only), clarithromycin, co-trimoxazole, fluconazole, and levofloxacin.

Infectious Disease Concepts and Considerations in the Diabetic Patient

Diabetic patients present their providers with unique clinical challenges when dealing with prevention and treatment of infectious diseases. By the very nature of their diabetes, these patients are at much higher risk of complications from seemingly benign infections as well as increasingly susceptible to more resistant or invasive disease. Targeted prevention where possible, regular follow-up, and early, aggressive treatment are crucial to diabetic patients’ longevity and quality of life. This review will focus on key vaccine-preventable issues as well as management of common conditions such as urinary tract infection and skin and soft tissue infection often seen in diabetic patients.

A Review of Levofloxacin for the Treatment of Bacterial Infections

Completing its initial phases of drug development in the mid 1990s as the one of the first fluoroquinolones that could be used with confidence to treat respiratory tract infections, levofloxacin went on to become one of the most widely prescribed antibiotics in the world. Available in both oral (po) and intravenous (IV) formulations and with characteristics of over 90% bioavailability, distribution into both extracellular and intracellular pulmonary compartments, highly predictable pharmacokinetics with over 90% of the drug being excreted unchanged in urine, and reliable activity against a broad spectrum of clinically important pathogens, levofloxacin has been used successfully to treat patients with a variety of serious infectious diseases as well as common infections most often treated outside of the hospital setting. Results of clinical trials involving patients with respiratory tract, urinary tract, and skin infections have consistently shown rates of clinical success and bacteriological eradication that were comparable to other widely used broad-spectrum agents. Regimens of levofloxacin, initially involving total daily doses of 250 mg to 500 mg, but more recently regimens involving 750 mg doses, have been shown to be safe and effective. Nearly a decade and a half of clinical experience has defined a safety and tolerability profile that permits data-driven assessment of the risks and benefits of using levofloxacin. As resistance to currently available fluoroquinolones has emerged, the clinical value of levofloxacin deserves continued evaluation. However, consistently high rates of susceptibility of clinically important bacteria, especially among those bacteria that commonly cause respiratory tract infections, such as Streptococcus pneumoniae and Haemophilus influenzae, suggest that this agent will continue to be a widely used well past the 20-year anniversary of its introduction into the antibacterial armamentarium.

The insulinotropic effect of fluoroquinolones

Antimicrobial fluoroquinolones induce, with strongly varying frequency, life-threatening hypoglycemias, which is explained by their ability to block K(ATP) channels in pancreatic B-cells and thus to initiate insulin secretion. In apparent contradiction to this, we observed that none of the fluoroquinolones in this study (gatifloxacin, moxifloxacin, ciprofloxacin, and a number of fluorophenyl-substituted compounds) initiated insulin secretion of perifused mouse islets when the glucose concentration was basal (5mM). Only when the glucose concentration was stimulatory by itself (10mM), the fluoroquinolones enhanced secretion. The fluoroquinolones were ineffective on SUR1 Ko islets, which do not have functional K(ATP) channels. All of these fluoroquinolones depolarized the membrane potential of mouse B-cells (patch-clamping in the whole-cell mode). Using metabolically intact B-cells (perforated-patch mode) however, 100microM of gatifloxacin, ciprofloxacin or moxifloxacin were unable to depolarize when the glucose concentration was 5mM, whereas other K(ATP) channel blockers (tolbutamide and efaroxan) remained effective. Only at a very high concentration (500microM) gatifloxacin and moxifloxacin, but not ciprofloxacin induced repetitive depolarizations which could be antagonized by diazoxide. In the presence of 10mM glucose all fluoroquinolones which enhanced secretion markedly elevated cytosolic calcium concentration ([Ca(2+)](i)). In the presence of 5mM glucose gatifloxacin and moxifloxacin at 500microM but not at 100microM elevated [Ca(2+)](i). It is concluded that fluoroquinolones in the clinically relevant concentration range are not initiators, but rather enhancers of glucose-induced insulin secretion. The block of K(ATP) channels appears necessary but not sufficient to explain the hypoglycemic effect of fluoroquinolones.