A dose-escalation study of the safety, tolerability, and pharmacokinetics of intravenous gatifloxacin in healthy adult men

Physicochemical Characteristics of Antimicrobials and Practical Recommendations for Intravenous Administration: A Systematic Review

Most antimicrobial drugs need an intravenous (IV) administration to achieve maximum efficacy against target pathogens. IV administration is related to complications, such as tissue infiltration and thrombo-phlebitis. This systematic review aims to provide practical recommendations about diluent, pH, osmolarity, dosage, infusion rate, vesicant properties, and phlebitis rate of the most commonly used antimicrobial drugs evaluated in randomized controlled studies (RCT) till 31 March 2023. The authors searched for available IV antimicrobial drugs in RCT in PUBMED EMBASE®, EBSCO® CINAHL®, and the Cochrane Controlled Clinical trials. Drugs' chemical features were searched online, in drug data sheets, and in scientific papers, establishing that the drugs with a pH of <5 or >9, osmolarity >600 mOsm/L, high incidence of phlebitis reported in the literature, and vesicant drugs need the adoption of utmost caution during administration. We evaluated 931 papers; 232 studies were included. A total of 82 antimicrobials were identified. Regarding antibiotics, 37 reach the "caution" criterion, as well as seven antivirals, 10 antifungals, and three antiprotozoals. In this subgroup of antimicrobials, the correct vascular access device (VAD) selection is essential to avoid complications due to the administration through a peripheral vein. Knowing the physicochemical characteristics of antimicrobials is crucial to improve the patient's safety significantly, thus avoiding administration errors and local side effects.

Chemical Classes Presenting Novel Antituberculosis Agents Currently in Different Phases of Drug Development: A 2010-2020 Review

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a curable airborne disease currently treated using a drug regimen consisting of four drugs. Global TB control has been a persistent challenge for many decades due to the emergence of drug-resistant Mtb strains. The duration and complexity of TB treatment are the main issues leading to treatment failures. Other challenges faced by currently deployed TB regimens include drug-drug interactions, miss-matched pharmacokinetics parameters of drugs in a regimen, and lack of activity against slow replicating sub-population. These challenges underpin the continuous search for novel TB drugs and treatment regimens. This review summarizes new TB drugs/drug candidates under development with emphasis on their chemical classes, biological targets, mode of resistance generation, and pharmacokinetic properties. As effective TB treatment requires a combination of drugs, the issue of drug-drug interaction is, therefore, of great concern; herein, we have compiled drug-drug interaction reports, as well as efficacy reports for drug combinations studies involving antitubercular agents in clinical development.

Usefulness of simultaneous and sequential monitoring of glucose level and electrocardiogram in monkeys treated with gatifloxacin under conscious and nonrestricted conditions

Drug-induced cardiac electrophysiological abnormalities accompanied by hypoglycemia or hyperglycemia increase the risk for life-threatening arrhythmia. To assess the drug-induced cardiotoxic potential associated with extraordinary blood glucose (GLU) levels, the effect of gatifloxacin (GFLX) which was frequently associated with GLU abnormality and QT/QTc prolongations in the clinic on blood GLU and electrocardiogram (ECG) parameters was investigated in cynomolgus monkeys (n=4) given GFLX orally in an ascending dose regimen (10, 30, 60 and 100 mg/kg). Simultaneous and sequential GLU and ECG monitoring with a continuous GLU monitoring system and Holter ECG, respectively, were conducted for 24 h under free-moving conditions. Consequently, GFLX at 30 and 60 mg/kg dose-dependently induced a transient decrease in GLU without any ECG abnormality 2–4 h postdose. Highest dose of 100 mg/kg caused severe hypoglycemia with a mean GLU of <30 mg/dL, accompanied by remarkable QT/QTc prolongations by 20–30% in all animals. In contrast, hyperglycemia without QT/QTc prolongations was noted 24 h after dosing in one animal. A close correlation between GLU and QTc values was observed in animals treated with 100 mg/kg, suggesting that GFLX-induced hypoglycemia enhanced QT/QTc prolongations. Furthermore, the 24-h sequential GLU monitoring data clearly distinguished between GFLX-induced GLU abnormality and physiological GLU changes influenced by feeding throughout the day. In conclusion, the combined assessment of continuous GLU and ECG monitoring is valuable in predicting the drug-induced cardio-electrophysiological risk associated with both GLU and ECG abnormalities.

What Role do Fluoroquinolone Antimicrobial Agents Play in Cardiac Dysfunction and Altered Glycemic Control?

This article focuses on the development of 2 major adverse drug events associated with some fluoroquinolone antimicrobial agents, specifically cardiac and glycemic effects. Cardiac dysfunction, including corrected QT (QTc) interval prolongation and torsades de pointes, has been linked to the administration of fluoroquinolones. The first indication of QTc prolongation was reportedwith sparfloxacin, and since that time, it has been associated with a number of other fluoroquinolones, leading to the assumption that this is a general class effect. Fluoroquinolone-associated effects on cardiac conduction appear more likely to occur in patients with underlying cardiac diseases, those with electrolyte abnormalities, and those coadministered antiarrhythmics and other QTc-prolonging drugs. Some fluoroquinolone agents have also been associated with alterations in glycemic control. Hypoglycemia and hyperglycemia have been reported with many of the currently available agents. Risk factors for aberrations in glucose homeostasis include noninsulindependent diabetes mellitus, increased age, impaired renal function, and the concomitant use of oral hypoglycemic agents. The widespread use of fluoroquinolones highlights the need for clinicians to consider predisposed populations and use caution when selecting antimicrobial therapies.

Dysglycemia associated with quinolones

Antimicrobial therapy is well known to be associated with fluctuations of blood glucose levels. This review aims at exploring the association between glycemic fluctuations and antibiotics mainly focusing on quinolones. Quinolones are associated with hypoglycemia and hyperglycemia. Several mechanism are proposed to explain this causality.

Comparative pharmacokinetics and bioavailability of gemifloxacin administered as an intravenous 200 mg formulation or an oral 320 mg tablet

BACKGROUND

Gemifloxacin is a synthetic fluoroquinolone antimicrobial agent, which has potent activity against most Gram-negative and Gram-positive organisms. It is indicated for the treatment of community-acquired pneumonia and acute bacterial exacerbation of chronic bronchitis.

OBJECTIVE

The aim of this study was to assess the clinical potential of a new gemifloxacin 200 mg intravenous formulation by comparing its pharmacokinetic characteristics with those of the branded Factive(®) gemifloxacin tablet.

METHODS

A single-dose, open-label, randomized-sequence, two-period crossover study was performed with 17 healthy male volunteers. The two treatment periods were separated by a 1-week washout period. Blood samples were taken for up to 48 h post-dose. Plasma gemifloxacin concentrations were determined by a validated high-performance liquid chromatography-tandem mass spectrometry method. To calculate the pharmacokinetic parameters, noncompartmental analysis was performed. The two formulations were considered to be pharmacokinetically equivalent if the 90 % confidence intervals (CIs) of the log-transformed ratios (intravenous/oral formulations) of the area under the plasma concentration-time curve (AUC) from time zero to the time of the last measurable concentration (AUClast) and the AUC from time zero to infinity (AUC∞) were within the standard bioequivalence range (0.8-1.25). Safety and tolerability were evaluated on the basis of physical examinations, vital signs, electrocardiograms, clinical laboratory tests and adverse event monitoring.

RESULTS

Seventeen subjects were enrolled, and 15 subjects completed the study. Sixteen subjects received intravenous 200 mg gemifloxacin and 15 received oral 320 mg gemifloxacin. The 15 subjects in the pharmacokinetic analysis set had a mean (standard deviation [SD]) age, height and weight of 27.2 (5.3) years, 173.5 (4.4) cm and 67.3 (7.4) kg, respectively. Both formulations had similar pharmacokinetic profiles. For the intravenous formulation, the mean (SD) AUClast, AUC∞ and maximum plasma concentration (C max) values were 9.12 (4.03) μg·h/mL, 9.26 (4.07) μg·h/mL and 2.90 (1.65) μg/mL, respectively, while these values for the oral formulation were 9.44 (3.34) μg·h/mL, 9.60 (3.49) μg·h/mL and 2.03 (0.95) μg/mL, respectively. For the intravenous and oral formulations, the median (range) time to reach C max (t max) values were 0.9 (0.7-1.0) and 1.0 (0.5-2.0) h, respectively. The mean relative bioavailability was 68.99 %. The 90 % CI of the ratios of the log-transformed values of AUClast and AUC∞ was 0.82-1.07. There were no serious adverse events. The intravenous and oral formulations were associated with treatment-emergent adverse event incidences of 63 % (10/16) and 13 % (2/15), respectively. After the intravenous formulation was administered, application site pain and paraesthesia were the most frequently reported adverse events (31 and 25 %, respectively). All adverse events resolved spontaneously without treatment.

CONCLUSION

Intravenous 200 mg and oral 320 mg formulations of gemifloxacin are equivalent in terms of AUC following a single dose in healthy male subjects.

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.).

Human organic cation transporters 1 (SLC22A1), 2 (SLC22A2), and 3 (SLC22A3) as disposition pathways for fluoroquinolone antimicrobials

Fluoroquinolones (FQs) are important antimicrobials that exhibit activity against a wide range of bacterial pathogens and excellent tissue permeation. They exist as charged molecules in biological fluids, and thus, their disposition depends heavily on active transport and facilitative diffusion. A recent review of the clinical literature indicated that tubular secretion and reabsorption are major determinants of their half-life in plasma, efficacy, and drug-drug interactions. In particular, reported in vivo interactions between FQs and cationic drugs affecting renal clearance implicated organic cation transporters (OCTs). In this study, 13 FQs, ciprofloxacin, enoxacin, fleroxacin, gatifloxacin, levofloxacin, lomefloxacin, moxifloxacin, norfloxacin, ofloxacin, pefloxacin, prulifloxacin, rufloxacin, and sparfloxacin, were screened for their ability to inhibit transport activity of human OCT1 (hOCT1) (SLC22A1), hOCT2 (SLC22A2), and hOCT3 (SLC22A3). All, with the exception of enoxacin, significantly inhibited hOCT1-mediated uptake under initial test conditions. None of the FQs inhibited hOCT2, and only moxifloxacin inhibited hOCT3 (~30%), even at a 1,000-fold excess. Gatifloxacin, moxifloxacin, prulifloxacin, and sparfloxacin were determined to be competitive inhibitors of hOCT1. Inhibition constants (K(i)) were estimated to be 250 ± 18 μM, 161 ± 19 μM, 136 ± 33 μM, and 94 ± 8 μM, respectively. Moxifloxacin competitively inhibited hOCT3-mediated uptake, with a K(i) value of 1,598 ± 146 μM. Despite expression in enterocytes (luminal), hepatocytes (sinusoidal), and proximal tubule cells (basolateral), hOCT3 does not appear to contribute significantly to FQ disposition. However, hOCT1 in the sinusoidal membrane of hepatocytes, and potentially the basolateral membrane of proximal tubule cells, is likely to play a role in the disposition of these antimicrobial agents.

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.

Fluoroquinolone disposition: identification of the contribution of renal secretory and reabsorptive drug transporters

INTRODUCTION

Fluoroquinolones (FQs) exist as charged molecules in blood and urine making their absorption, distribution, and elimination likely to be influenced by active transport mechanisms. Greater understanding of in vivo FQ clearance mechanisms should help improve the predictability of drug-drug interactions, enhance the clinical safety and efficacy, and aid future novel drug design strategies.

AREAS COVERED

The authors present an overview of FQ development and associated drug-drug interactions, followed by systematic quantitative review of the physicochemical and in vivo pharmacokinetic properties for 15 representative FQs using historical clinical literature. These results were correlated with in vitro studies implicating drug transporters in FQ clearance to link clinical and in vitro evidence supporting the contribution of drug transport mechanisms to FQ disposition. Specific transporters likely to handle FQs in human renal proximal tubule cells are also identified.

EXPERT OPINION

Renal handling, that is, tubular secretion and reabsorption, appears to be the main determinant of FQ plasma half-life, clinical duration of action, and drug-drug interactions. Due to their zwitterionic nature, FQs are likely to interact with organic anion and cation transporters within the solute carrier (SLC) superfamily, including OAT1, OAT3, OCT2, OCTN1, OCTN2, MATE1, and MATE2. The ATP-binding cassette (ABC) transporters MDR1, MRP2, MRP4, and BCRP also may interact with FQs.

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.

An evaluation of the effects of gatifloxacin on glucose homeostasis

INTRODUCTION

The United States labeling for gatifloxacin has been updated to include contradictions related to its reported association with dysglycemia. However, adequately controlled studies in acute care settings assessing the magnitude and clinical determinants of dysglycemia are lacking.

OBJECTIVES

To compare the hypoglycemic and hyperglycemic effects of gatifloxacin with ceftriaxone in hospitalized patients.

METHODS

A retrospective cohort study of hospitalized adult (> or =18 years) patients admitted with Community Acquired Pneumonia (CAP) or Acute Exacerbation of Chronic Bronchitis (AECB) in a US tertiary care hospital between 7/1/01 and 12/31/04 treated with gatifloxacin or ceftriaxone during hospital admission. Outcomes of interests were incidence of hypoglycemia (blood glucose levels <46 mg/dL) or hyperglycemia (>200 mg/dL) during up to 5 days of drug exposure. Risks for gatifloxacin and ceftriaxone were compared adjusting for variables previously reported to be independent predictors of hypoglycemia or hyperglycemia.

RESULTS

1504 patients met the study inclusion criteria. Compared to ceftriaxone, gatifloxacin was associated with an increased risk of hypoglycemia: (adjusted odds ratio (OR) 2.34, 95% confidence interval (CI) 1.4-4.0). The increased risk of hypoglycemia during exposure to gatifloxacin was similar in patients with and without a diagnosis of diabetes mellitus. Gatifloxacin was not associated with an increased risk for hyperglycemia (adjusted OR: 1.06 95% CI 0.8-1.4) considering the whole study cohort. However, stratification by diagnosis of diabetes, gatifloxacin treated patients appeared to have a reduced risk of hyperglycemia (adjusted OR: 0.4 95% CI 0.2-0.4) while non-diabetic gatifloxacin treated patients appeared to have an increased risk of hyperglycemia (adjusted OR: 1.64 95% CI 1.1-2.4).

CONCLUSION

The risk of dysglycemia with gatifloxacin in this population of hospitalized patients was not as high as previously reported in ambulatory patients. Although these results suggest gatifloxacin use is safer in acute care settings, we recommend that clinicians monitor blood glucose levels carefully or consider alternatives to gatifloxacin therapy whenever possible.

Pharmacokinetics and pharmacodynamics of gatifloxacin in children with recurrent otitis media: application of sparse sampling in clinical development

Gatifloxacin is a 4th-generation fluoroquinolone previously under investigation for the treatment of otitis media in infants and children. These analyses were designed to evaluate the extent of drug exposure relative to adult populations and to examine the relationship between drug exposure and response to therapy in children with recurrent otitis media or early treatment failures of acute otitis media. The patient population included 187 patients from an open-label, multicenter, noncomparative study using gatifloxacin 10 mg/kg once daily. Gatifloxacin exposure was estimated using a single steady-state blood sample in conjunction with a pharmacostatistical model developed using a separate pediatric data set. Gatifloxacin exposure was equivalent to that in adults given 400 mg daily. Of the 41 patients who had Streptococcus pneumoniae from middle ear culture, there were only 3 bacteriologic failures; there was no relationship between plasma fu AUC(0-24):MIC ratio and outcome. In conclusion, population pharmacokinetic/pharmacodynamic methods allowed estimation of drug exposure using one sample per patient.

High performance liquid chromatography for quantification of gatifloxacin in rat plasma following automated on-line solid phase extraction

An automated system using on-line solid phase extraction and HPLC with fluorimetric detection was developed and validated for quantification of gatifloxacin in rat plasma. The extraction was carried out using C(18) cartridges (BondElut), with a high extraction yield. After washing, gatifloxacin was eluted from the cartridge with mobile phase onto a C(18) HPLC column. The mobile phase consisted of a mixture of phosphoric acid (2.5mM), methanol, acetonitrile and triethylamine (64.8:15:20:0.2, v/v/v/v, apparent pH(app.) 2.8). All samples and standard solutions were chromatographed at 28 degrees C. The method developed was selective and linear for drug concentrations ranging between 20 and 600 ng/ml. Gatifloxacin recovery ranged from 95.6 to 99.7%, and the limit of quantification was 20 ng/ml. The intra and inter-assay accuracy were up to 94.3%. The precision determined not exceed 5.8% of the CV. High extraction yield up to 95% was obtained. Drug stability in plasma was shown in freezer at -20 degrees C up to 1 month, after three freeze-thaw cycles and for 24h in the autosampler after processing. The assay has been successfully applied to measure gatifloxacin plasma concentrations in pharmacokinetic study in rats.

Evaluation of gatifloxacin pharmacokinetics and pharmacodynamics in severely ill adults in a medical Intensive Care Unit

A prospective, open-label study investigated the steady-state pharmacokinetics of gatifloxacin in 20 adult patients in a medical Intensive Care Unit (ICU). Twelve patients had normal or moderately impaired renal function (creatinine clearance (CrCL) >or=40 mL/min) and received gatifloxacin 400 mg intravenously once daily. Eight patients had CrCL<40 mL/min and received 200 mg doses. Gatifloxacin plasma and urine concentrations were determined by validated high-performance liquid chromatography. Mean+/-standard deviation gatifloxacin elimination half-life (t(1/2)), systemic clearance and volume of distribution in patients with CrCL>or=40 mL/min were 10.8+/-1.5h, 156+/-29 mL/min and 1.8+/-0.2 L/kg, respectively. Maximum and minimum serum concentrations (C(max) and C(min)) and area under the serum concentration-time curve from 0-24 h (AUC(0-24)) in these patients were 4.77+/-0.76 mg/L, 1.08+/-0.28 mg/L and 44.4+/-9.2 mgh/L, respectively. Observed t(1/2), C(max) and AUC(0-24) following 200 mg doses in patients with poor renal function (CrCL<40 mL/min) were 18.2+/-3.3 h, 2.85+/-0.76 mg/L and 36.6+/-3.4 mgh/L, respectively. Statistically significant (P<0.05) increase in AUC(0-24) and decreases in t(1/2) and clearance (total and renal) were observed in ICU patients administered intravenous gatifloxacin compared with previous data in healthy volunteers. Pharmacodynamic evaluation by Monte Carlo simulation indicated that approved gatifloxacin dosage regimens appear to be adequate for most pathogens (minimum inhibitory concentration (MIC) <or=0.5 microg/mL) associated with community-acquired infections in severely ill ICU patients; less susceptible pathogens (MIC>or=1 microg/mL) do not appear to be optimally treated with currently approved doses.

Plasma Concentrations, Pharmacokinetics and Urinary Excretion of Gatifloxacin after Single Intravenous Injection in Buffalo Calves

The pharmacokinetics and urinary excretion of gatifloxacin were investigated after a single intravenous injection of 4 mg/kg body weight in buffalo calves. The therapeutic plasma drug concentration was maintained for up to 12 h. Gatifloxacin rapidly distributed from blood to tissue compartments, which was evident from the high values of the distribution rate constant, alpha1 (11.1 +/- 1.06 h(-1)) and the rate constant of transfer of drug from central to peripheral compartment, k12 (6.29 +/- 0.46 h(-1)). The area under the plasma drug concentration-time curve and apparent volume of distribution were 17.1 +/- 0.63 (microg.h)/ml and 3.56 +/- 0.95 L/kg, respectively. The elimination half-life (t (1/2 beta)), total body clearance (ClB) and the ratio of drug present in tissues and plasma (T/P) were 10.4 +/- 2.47 h, 235.1 +/- 8.47 ml/(kg.h) and 10.1 +/- 2.25, respectively. About 19.7% of the administered drug was excreted in urine within 24 h. A satisfactory intravenous dosage regimen for gatifloxacin in buffalo calves would be 5.3 mg/kg at 24 h intervals.

Gatifloxacin-Induced Hyperglycemia: A Review of 4 Cases and the Literature

Gatifloxacin, a broad-spectrum fluoroquinolone, has recently been voluntarily withdrawn by Bristol-Myers Squibb from the market secondary to dysglycemic events associated with this agent. Risk factors for this adverse event include diabetes and those who are elderly (65 years of age or older), have renal insufficiency, or take glucose altering medications. The mechanism for this adverse reaction is not fully understood. However, it is theorized that there is an association between accumulation of gatifloxacin (particularly in elderly patients or those with renal insufficiency) and dysglycemic events with gatifloxacin. A review of the literature found 13 reported cases of hyperglycemia induced by gatifloxacin and 2 clinical trials evaluating gatifloxacin's association with hyperglycemia. Similarly to other reported cases, the authors' 4 outpatients were initiated on gatifloxacin therapy and subsequently had developed hyperglycemia during gatifloxacin therapy. Prior to the multiple observations of dysglycemias associated with gatifloxacin, this medication was widely used and thought to have an excellent safety profile. Hence, clinicians should be vigilant and exercise caution with newly approved medications.

Outpatient gatifloxacin therapy and dysglycemia in older adults

BACKGROUND

Gatifloxacin has been associated with both hypoglycemia and hyperglycemia. We examined dysglycemia-related health outcomes associated with various antibiotics in a population of approximately 1.4 million Ontario, Canada, residents 66 years of age or older.

METHODS

We conducted two population-based, nested case-control studies. In the first, case patients were persons treated in the hospital for hypoglycemia after outpatient treatment with a macrolide, a second-generation cephalosporin, or a respiratory fluoroquinolone (gatifloxacin, levofloxacin, moxifloxacin, or ciprofloxacin). In the second, case patients were persons who received hospital care for hyperglycemia. For each case patient, we identified up to five controls matched according to age, sex, the presence or absence of diabetes, and the timing of antibiotic therapy.

RESULTS

Between April 2002 and March 2004, we identified 788 patients treated for hypoglycemia within 30 days after antibiotic therapy. As compared with macrolide antibiotics, gatifloxacin was associated with an increased risk of hypoglycemia (adjusted odds ratio, 4.3; 95 percent confidence interval, 2.9 to 6.3). Levofloxacin was also associated with a slightly increased risk (adjusted odds ratio, 1.5; 95 percent confidence interval, 1.2 to 2.0), but no such risk was seen with moxifloxacin, ciprofloxacin, or cephalosporins. We then identified 470 patients treated for hyperglycemia within 30 days after antibiotic therapy. As compared with macrolides, gatifloxacin was associated with a considerably increased risk of hyperglycemia (adjusted odds ratio, 16.7; 95 percent confidence interval, 10.4 to 26.8), but no risk was noted with the other antibiotics. Risks were similar in the two studies regardless of the presence or absence of diabetes.

CONCLUSIONS

As compared with the use of other broad-spectrum oral antibiotics, including other fluoroquinolones, the use of gatifloxacin among outpatients is associated with an increased risk of in-hospital treatment for both hypoglycemia and hyperglycemia.

A retrospective, comparative evaluation of dysglycemias in hospitalized patients receiving gatifloxacin, levofloxacin, ciprofloxacin, or ceftriaxone

STUDY OBJECTIVES

To compare rates of blood glucose abnormalities in hospitalized patients receiving fluoroquinolones or ceftriaxone, and to describe the characteristics of patients who develop blood glucose abnormalities while receiving these agents.

DESIGN

Retrospective chart review.

SETTING

Two community-based hospitals in the Houston, Texas, region.

PATIENTS

Seventeen thousand one hundred eight patients who received fluoroquinolones or ceftriaxone; of those, 101 received levofloxacin, gatifloxacin, or ceftriaxone and also had serum glucose concentrations above 200 or below 50 mg/dl within 72 hours of receiving the drug.

MEASUREMENTS AND MAIN RESULTS

Baseline demographics of patients with glucose abnormalities while receiving gatifloxacin, levofloxacin, or ceftriaxone were similar. Mean +/- SD patient age, weight, and estimated creatinine clearance were 67 +/- 17 years, 79 +/- 21 kg, and 52 +/- 32 ml/minute, respectively. Dysglycemia rates relative to treatment were as follows: gatifloxacin 76 (1.01%) of 7540 patients, levofloxacin 11 (0.93%) of 1179, ceftriaxone 14 (0.18%) of 7844, ciprofloxacin 0 (0%) of 545, and any fluoroquinolone 87 (0.94%) of 9264. Dysglycemia was more likely to occur in patients receiving any fluoroquinolone than in those receiving ceftriaxone (relative risk [RR] 3.32, 95% confidence interval (CI) 2.31-4.78, p < 0.05). The rate of dysglycemia did not differ with gatifloxacin and levofloxacin (RR 1.07, 95% CI 0.62-1.86, p = 0.8). Of the 101 patients with dysglycemias, hypoglycemia occurred in nine (9%) and hyperglycemia in 92 (91%). In a multivariate analysis of patients receiving fluoroquinolones, only concomitant sulfonylurea therapy was identified as an independent risk factor for development of hypoglycemia compared with patients who experienced hyperglycemia.

CONCLUSION

In the 17,108 patients receiving a fluoroquinolone or ceftriaxone, the rate of dysglycemia was greater in those receiving levofloxacin or gatifloxacin than in those receiving ceftriaxone. However, no difference was noted in the rate of glucose abnormalities with levofloxacin versus gatifloxacin. Clinicians should be aware of dysglycemic events that may occur in patients receiving fluoroquinolones, especially in those with diabetes mellitus or those receiving sulfonylureas.

Effect of Ensure on the Oral Bioavailability of Gatifloxacin in Healthy Volunteers

STUDY OBJECTIVE

To determine the effect of Ensure on the relative oral bioavailability of gatifloxacin in healthy volunteers.

DESIGN

Single-dose, randomized, crossover study.

SETTING

University-affiliated research center.

SUBJECTS

Twelve healthy volunteers (six men, six women) aged 18 years or older with no clinically significant abnormal findings on physical examination or in medical history. Intervention. Subjects consumed 120 ml of study liquid-water or Ensure-every 30 minutes for five doses. With the second dose, subjects ingested a single gatifloxacin 400-mg tablet that had been uniformly crushed and mixed into the study liquid.

MEASUREMENTS AND MAIN RESULTS

Serial blood samples were collected for 48 hours, and gatifloxacin concentrations were determined by high-performance liquid chromatography. Pharmacokinetic data were analyzed by using noncompartmental methods. Maximum serum concentration (Cmax) and area under the serum concentration-time curve from zero to infinity (AUC0-infinity) were tested for bioequivalence after log-transformation of the data. Comparison of parameters for gatifloxacin administered with water versus those with Ensure showed that Cmax (4.35 +/- 0.90 vs 2.41 +/- 0.58 mug/ml, p<0.0001) and AUC(0-infinity) (42.4 +/- 10.1 vs 31.3 +/- 8.3 mg*hr/L, p<0.0001) were significantly decreased with Ensure, and bioequivalence was not achieved for either parameter. The geometric least squares mean ratio was 0.553 (90% confidence interval [CI] 0.501-0.611) for Cmax and 0.730 (90% CI 0.664-0.802) for AUC0-infinity. The median time to reach Cmax was significantly prolonged when gatifloxacin was administered with Ensure versus that with water (2.5 hrs vs 1.0 hr, p=0.006).

CONCLUSIONS

The Cmax and AUC0-infinity of gatifloxacin were significantly decreased when the drug was administered with Ensure. The clinical significance of these findings will depend on the offending pathogen and its susceptibility to gatifloxacin.

Hypoglycemia Associated with the Use of Gatifloxacin

We present the histories, clinical findings, and hospital course of three patients who developed hypoglycemia after receiving gatifloxacin. Possible mechanisms for the hypoglycemia are outlined. CASE 1: A 89-year-old diabetic male receiving glyburide was given a single dose of gatifloxacin for bronchitis. Thirteen hours later, he was found to be unresponsive with a blood glucose level of 34 mg/dL. The hypoglycemia resolved within 24 hours of stopping gatifloxacin. CASE 2: A 80-year-old nondiabetic woman with end-stage renal disease and recent surgery was treated with gatifloxacin, cefepime, and metronidazole for pneumonia. Sixteen hours later, her serum glucose level was 61 mg/dL, and over the next 24 hours was as low as 39 mg/dL. The hypoglycemia resolved within 40 hours of stopping gatifloxacin. CASE 3: A 58-year-old diabetic man receiving glyburide was admitted for myocardial infarction and renal failure. Twelve hours after receiving gatifloxacin for pneumonia, his blood glucose level was 60 mg/dL and was as low as 42 mg/dL between 2 and 22.5 hours of a second dose of gatifloxacin. The hypoglycemia resolved within 24 hours of stopping gatifloxacin.

CONCLUSIONS

Gatifloxacin use may precipitate hypoglycemia in diabetic patients receiving oral hypoglycemic agents and in nondiabetic patients with chronic renal failure. Discontinuation of gatifloxacin results in improvement in glucose homeostasis.

Severe Hyperglycemia During Renally Adjusted Gatifloxacin Therapy

OBJECTIVE

To report a case of severe hyperglycemia in a nondiabetic patient receiving gatifloxacin that was properly dosed based on renal function.

CASE SUMMARY

A 65-year-old nondiabetic female with progressive renal dysfunction was admitted for severe hyperglycemia. The patient had received 9 days of a 10-day course of renally adjusted therapy with gatifloxacin 200 mg/day for bronchitis. Her blood glucose level on admission was 1121 mg/dL, at which point the gatifloxacin was discontinued. After several days of intensive insulin therapy, the blood glucose levels returned to normal, and the patient was subsequently discharged.

DISCUSSION

Gatifloxacin-induced hyperglycemia has been reported in the literature, but based on a MEDLINE search (1966–December 2004), no such cases were found in a nondiabetic patient receiving the proper gatifloxacin dose, adjusted for degree of renal insufficiency. The available case reports seem to suggest the increase in blood glucose concentrations could have been precipitated by high drug concentrations in patients not receiving the renally adjusted dose or in those with preexisting, undiagnosed diabetes. A definite mechanism of action for gatifloxacin-induced hyperglycemia is not known. The Naranjo probability scale revealed a probable adverse reaction of hyperglycemia associated with gatifloxacin therapy.

CONCLUSIONS

Healthcare professionals should be more aware of the possible development of hyperglycemia in all patients taking gatifloxacin, including those who are not diabetic and those receiving appropriately reduced doses for renal dysfunction.

Gatifloxacin: a review of its use in the treatment of bacterial infections in the US

Gatifloxacin (Tequin) is an 8-methoxy fluoroquinolone approved in the US for use in the treatment of community-acquired pneumonia (CAP), acute exacerbations of chronic bronchitis (AECB), acute sinusitis, uncomplicated and complicated urinary tract infections (UTIs), pyelonephritis, gonorrhoea and uncomplicated skin and skin structure infections. Gatifloxacin has a broad spectrum of antibacterial activity in vitro and good clinical and bacteriological efficacy in patients with indicated infections following once-daily administration by the intravenous or oral routes. It is generally well tolerated; the most common adverse events are associated with the gastrointestinal tract and CNS. Recent approvals for the use of gatifloxacin in the treatment of CAP due to multidrug-resistant Streptococcus pneumoniae (MDRSP) and in uncomplicated skin and skin structure infections extend the role of this drug in the treatment of bacterial infections in the US.

Pharmacokinetics of gatifloxacin in infants and children

Gatifloxacin is an 8-methoxy fluoroquinolone effective against a broad spectrum of pathogens common in pediatric infections. The safety and pharmacokinetics of a single dose of gatifloxacin were studied in pediatric patients from 6 months to 16 years of age. Seventy-six pediatric patients (average age, 6.7 +/- 5.0 years) were administered a single oral dose of gatifloxacin suspension (5, 10, or 15 mg/kg of body weight; 600-mg maximum) in a dose-escalating manner. Subjects were stratified by age into 4 groups. An additional 12 children, greater than 6 years of age, received gatifloxacin as the tablet formulation at a dose of approximately 10 mg/kg. Gatifloxacin's apparent clearance and half-life were 5.5 +/- 2.1 ml/min/kg and 5.1 +/- 1.4 h. The maximum concentration of drug in plasma and area under the concentration-time curve (AUC) increased in a manner approximately proportional to the dose. At the 10-mg/kg dose, the bioavailability was similar between the suspension and tablet formulation. The apparent oral clearance of gatifloxacin, normalized for body weight, exhibited a small but statistically significant decrease with increasing age. In all subjects receiving gatifloxacin at 10 mg/kg, the AUC exceeded 20 microg . h/ml (estimated free AUC/MIC ratio of > or =34 for MIC of < or =0.5 microg/ml). These data suggest that gatifloxacin at a dose of 10 mg/kg every 24 h will achieve therapeutic concentrations in plasma in infants and children.

Comparison of ophthalmic gatifloxacin 0.3% and ciprofloxacin 0.3% in healing of corneal ulcers associated with Pseudomonas aeruginosa-induced ulcerative keratitis in rabbits

OBJECTIVE

Evaluation of gatifloxacin 0.3% ophthalmic solution efficacy in a corneal ulcer model of Pseudomonas keratitis.

METHODS

Heptanol-induced corneal ulcers in New Zealand White rabbits (n = 41; 8 females/group) were inoculated with 10(6) CFU of Pseudomonas aeruginosa. Gatifloxacin 0.3% dosing varied among 4 groups with frequencies of 16-48 doses/day (days 1-2), 3-16 doses/day (days 3-7), and maintenance dosing of 3-4 doses/day (days 8-22). Ciprofloxacin 0.3% was administered as labeled for corneal ulcers, with 44 doses on day 1, 16 doses on day 2, and 4 doses/day on days 3-21.

RESULTS

All eyes showed evidence of infection by 48 hours postinoculation with 36 of 41 eyes (87.8%) exhibiting moderate-to-severe keratitis. All eyes exhibited corneal healing by day 15, with no significant differences among groups. Three of 4 groups receiving gatifloxacin tended to have smaller fluorescein retention area scores than did the ciprofloxacin group. No eyes tested positive for Pseudomonas at the end of the study. No corneal precipitates were found following as many as 48 doses/day of gatifloxacin.

CONCLUSION

Ophthalmic gatifloxacin 0.3% is at least as effective as ciprofloxacin at healing corneal ulcers infected with Pseudomonas aeruginosa when gatifloxacin is administered less frequently than ciprofloxacin. Trends favored gatifloxacin in fluorescein retention scores.

Pharmacokinetic Considerations in the Treatment of Tuberculosis in Patients with Renal Failure

Tuberculosis is re-emerging in patients with altered immune status, such as those with chronic renal failure. Clinicians should thus be aware of the pharmacokinetics and dosage adjustment of antitubercular drugs in patients with renal insufficiency. Among patients with renal insufficiency, those who are dialysed should be treated with special care. Indeed, dosage should always be closely adjusted in these patients and potential removal by dialysis must be taken into account. However reliable the dosage adjustment recommendations are for these drugs in patients with renal failure, further pharmacokinetic investigations need to be performed, especially in dialysis patients in whom the influence of haemodialysis and continuous ambulatory peritoneal dialysis on drug pharmacokinetics needs to be detailed. In the meantime, it could be generally advised to administer all antitubercular drugs after the haemodialysis session, even though some drugs are known to be non-dialysable.

Fatal Hypoglycemia Associated with Levofloxacin

Fluoroquinolones are generally regarded as safe antimicrobial agents with relatively few adverse effects or drug interactions. Thus, they enjoy widespread use for treatment of community- and hospital-acquired infections. Although uncommon, hypoglycemia has been reported with all the fluoroquinolones and appears to occur most frequently in elderly patients with type 2 diabetes mellitus who are receiving therapy with oral hypoglycemics. The exact mechanism of this effect is unknown but is postulated to be a result of blockage of adenosine 5'-triphosphate-sensitive potassium channels in pancreatic beta-cell membranes. We report a case of fatal hypoglycemia related to levofloxacin administration in an elderly patient with diabetes. As with other fluoroquinolones, levofloxacin can cause profound and prolonged hypoglycemia. Clinicians should be cognizant of this potential adverse effect in patients with diabetes who are receiving levofloxacin therapy.

Severe Hyperglycemia During Gatifloxacin Therapy in Patients without Diabetes

OBJECTIVE

To present two cases of severe hyperglycemia in patients without diabetes who received gatifloxacin therapy.

METHODS

We describe the histories, clinical findings, and hospital courses of two women in whom severe hyperglycemia developed after gatifloxacin therapy was initiated. Interacting factors that may result in severe hyperglycemia in patients without diabetes and the literature explaining the mechanism by which gatifloxacin can alter glucose metabolism are reviewed.

RESULTS

Our first patient, a 46-year-old woman with end-stage renal disease, presented with a 3-day history of fever, abdominal pain, and hypotension. Admission laboratory data included a fasting plasma glucose level of 72 mg/dL and a glycosylated hemoglobin of 5.3%. She was treated with gatifloxacin for an infected ovarian cyst found on laparotomy. Her subsequent glucose values ranged from 400 to 500 mg/dL and remained high during gatifloxacin therapy. Antibiotic treatment was changed to ciprofloxacin. On outpatient follow-up, the patient's fasting plasma glucose levels had decreased to a range of 87 to 108 mg/dL. Our second patient, a 77-year-old woman with a history of chronic renal failure and congestive heart failure, was hospitalized because of dyspnea and hypotension. She was given gatifloxacin for a urinary tract infection. Her daily fasting plasma glucose value gradually increased from 100 mg/dL on admission to 694 mg/dL on the 6th hospital day. The patient required insulin therapy throughout her hospitalization, and she died on the 12th hospital day.

CONCLUSION

Gatifloxacin therapy may precipitate severe hyperglycemia in patients without diabetes, especially in the elderly population, those with renal insufficiency, and those receiving multiple drugs known to alter glucose metabolism. Discontinuation of gatifloxacin treatment may result in improved glucose homeostasis.

Treatment of rabbit corneal infections with ophthalmic gatifloxacin: a concentration dependence study

This study was designed to determine the most effective dose of gatifloxacin in ophthalmic solution for control of methicillin-resistant Staphylococcus aureus (MRSA) corneal infections in rabbits. Rabbits were inoculated by injecting 9300 colony-forming units of MRSA into the corneal stroma of the eye (n=43). They were then randomly assigned to topical administration of saline, ofloxacin 0.3%, or gatifloxacin 0.02%, 0.1%, 0.3%, or 0.5% ophthalmic solutions. Infection severity 48 hours postinoculation was assessed by masked observers using standard scales. After treatment completion, viable MRSA in corneal tissue were counted, and pathologic examinations of ocular tissues were conducted. Relative to saline, treatment with gatifloxacin 0.3% or 0.5% decreased mean infection scores at every time point from 16 to 48 hours after inoculation (P < or = .012) and reduced area-under-the-curve values for infection scores by 50.3% and 54.2%, respectively (P = .00005). Rabbits treated with gatifloxacin 0.3% and 0.5% had lower area-under-the-curve values than those treated with ofloxacin 0.3% (P < or = .039). Viable MRSA in corneal tissue after gatifloxacin 0.3% or 0.5% treatment were decreased to less than 1% of those found after ofloxacin 0.3% treatment. Gram-positive colony formation and abscesses found in saline-treated corneas were distinctly alleviated by treatment with gatifloxacin 0.3% or 0.5%. No significant differences were observed between treatments with gatifloxacin 0.3% or 0.5% ophthalmic formulations and they were equally effective. Topical administration of gatifloxacin 0.3% or 0.5% ophthalmic solutions controlled MRSA corneal infections in rabbits significantly better than saline or ofloxacin 0.3%.

Pharmacokinetics and pharmacodynamics of gatifloxacin against Streptococcus pneumoniae and Staphylococcus aureus in a granulocyte-rich exudate

The pharmacokinetics of gatifloxacin were assessed in serum and in skin blister fluid (SBF), as was the pharmacodynamic activity in SBF. Five hours after a single dose of gatifloxacin, SBF killed 2.5 logs of Streptococcus pneumoniae and 1.5 log of Staphylococcus aureus during a 2-h incubation ex vivo.

Fluoroquinolones for the treatment of outpatient community-acquired pneumonia

The increasing prevalence of beta-lactam and macrolide resistance in bacteria that cause respiratory infections has underscored the need for effective antimicrobial agents. The broad spectrum, excellent oral bioavailability, and once-daily dosing of fluoroquinolones contributed to the introduction of several new agents in the past decade. This class is among the world's most used antimicrobial therapies in community and hospital settings. Fluoroquinolones are generally well tolerated, but safety profiles differ widely among agents. Knowledge of in vitro activity, local microbiologic susceptibility and resistance patterns, adverse effects, and potential drug interactions should influence the selection of the best agent for individual patients. This overview of the fluoroquinolones directs particular attention to use in community-acquired pneumonia and safety.

Efficacy and safety of gatifloxacin in elderly outpatients with community-acquired pneumonia

To evaluate the safety and efficacy of gatifloxacin in adults <65, 65 to 79, or > or =80 years old with community-acquired pneumonia, adult male and female outpatients from general community-based practices were enrolled in an open-label, multicenter, noncomparative study. Gatifloxacin 400 mg once daily was administered for seven to 14 days. Medical history, physical examination, signs and symptoms of infection, Gram stain and culture if specimen available, clinical response, and safety were determined. Of 1655 treated patients, 1103 were at least 65 years old, 405 were 65 to 79, and 147 were at least 80. Patients > or =80 years old presented with chills, chest pain, fever, or headache less often than younger patients. Cure rates were 95.5% for patients <65 years old, 96.2% for those 65 to 79, and 90.2% for those at least 80 years old. Neither the frequency nor susceptibility of isolated pathogens appeared to differ with age. Between 93.7% and 100% of subsets of the two younger groups with verified Streptococcus pneumoniae or Hemophilus influenzae were cured. All oldest-group patients in the subset with verified S. pneumoniae and 71.4% (7) of patients with H. influenzae were cured. Each age group, including current or past smokers and patients receiving medications for concomitant conditions, tolerated treatment well. Gatifloxacin is safe and efficacious in adults of any age with community-acquired pneumonia, including the elderly up to 100 years old and patients with S. pneumoniae including penicillin-resistant strains.

Gatifloxacin in community-based treatment of acute respiratory tract infections in the elderly

The elderly are at increased risk for respiratory tract infections. To evaluate the safety and efficacy of gatifloxacin in adults of any age with community-acquired respiratory tract infections, this open-label, multicenter, noncomparative study in community-based practices enrolled male and female outpatients at least 18 years old with a clinical diagnosis of community-acquired pneumonia (CAP), acute-bacterial exacerbation of chronic bronchitis (AECB), or acute uncomplicated maxillary sinusitis. Gatifloxacin 400 mg was administered once daily for seven to 14 days. Of 14781 clinically evaluable patients, 2505 were at least 65 years old, 499, at lest 80. Cure rates for CAP, AECB, and sinusitis ranged from 91.6% to 95.5% for patients less than 65 years old, 91.1% to 96.2% for those 65 to 79 years of age, and 89.5% to 94.8% for those at least 80 years old. Each age group, including patients with concomitant cardiovascular or diabetic conditions, tolerated treatment well. Gatifloxacin is efficacious and well tolerated in adult outpatients of any age with respiratory tract infections and is an important therapeutic option, particularly in communities with a high prevalence of resistant pathogens.

Gatifloxacin: a review of its use in the management of bacterial infections

Gatifloxacin is an 8-methoxy fluoroquinolone antibacterial agent. The drug has a broader spectrum of antibacterial activity than the older fluoroquinolones (e.g. ciprofloxacin) and shows good activity against many Gram-positive and Gram-negative pathogens, atypical organisms and some anaerobes. Notably, gatifloxacin is highly active against both penicillin-susceptible and -resistant strains of Streptococcus pneumoniae, a common causative pathogen in community-acquired pneumonia (CAP), acute sinusitis and acute bacterial exacerbations of bronchitis. Gatifloxacin is absorbed well from the gastrointestinal tract (oral bioavailability is almost 100%). Therefore, patients can be switched from intravenous to oral therapy without an adjustment in dosage. High concentrations of gatifloxacin are achieved in plasma and target tissues/fluids. Gatifloxacin has a long plasma elimination half-life, thus allowing once-daily administration. Few clinically significant interactions between gatifloxacin and other drugs have been reported. In patients with CAP, clinical response rates in recipients of intravenous/oral gatifloxacin 400 mg/day ranged from 86.8 to 98.0% and rates of bacterial eradication ranged from 83.1 to 100% (up to 28 days post-treatment). Gatifloxacin showed efficacy similar to that of amoxicillin/clavulanic acid, ceftriaxone (with or without erythromycin) with or without stepdown to clarithromycin, levofloxacin or clarithromycin. Gatifloxacin was as effective as clarithromycin or amoxicillin/clavulanic acid, and was significantly more effective (in terms of clinical response; p < 0.035) than 7 to 10 days' treatment with cefuroxime axetil in the treatment of acute exacerbations of chronic bronchitis. In acute sinusitis, gatifloxacin showed clinical efficacy similar to that of clarithromycin, trovafloxacin or amoxicillin/clavulanic acid. Genitourinary infections were also successfully treated with gatifloxacin. Gatifloxacin is generally well tolerated. Its tolerability profile was broadly similar to those of comparator agents in comparative trials. The most common adverse events are gastrointestinal symptoms (oral formulation) and injection site reactions.

CONCLUSIONS

Gatifloxacin has an extended spectrum of antibacterial activity and provides better coverage of Gram-positive organisms (e.g. S. pneumoniae) than some older fluoroquinolones. The drug has favourable pharmacokinetic properties, is administered once daily and is at least as well tolerated as other fluoroquinolones. Gatifloxacin is a useful addition to the fluoroquinolones currently available for use in the clinical setting and has an important role in the management of adult patients with various bacterial infections. As with other fluoroquinolones, careful control of gatifloxacin usage in the community is important in order to prevent the emergence of bacterial resistance and thus preserve the clinical value of this agent.

Broth microdilution and E-test for determining fluoroquinolone activity against Streptococcus pneumoniae

OBJECTIVE

To compare broth microdilution and E-test minimum inhibitory concentrations (MICs) of 4 fluoroquinolones against Streptococcus pneumoniae and to determine the effect of these in vitro MIC methods on the calculation of AUC00-24/MIC ratios.

METHODS

Levofloxacin, gatifloxacin, moxifloxacin, and gemifloxacin MICs were determined by broth microdilution (incubated in air) and E-test (incubated in CO2) for 100 clinical isolates of S. pneumoniae. MIC50, MIC90, and geometric mean MIC were calculated. Steady-state serum concentration-time profiles were simulated for once-daily, oral dosing of levofloxacin 500 mg, gatifloxacin 400 mg, moxifloxacin 400 mg, and gemifloxacin 320 mg. After correcting for protein binding, AUC0-24 of unbound drug was calculated for each regimen, and AUC0-24/MIC ratios were calculated using MIC data from both in vitro methods. Differences in MICs between methods were determined for each agent using the paired t-test (after logarithmic transformation of MICs) and the Wilcoxon signed-rank test. Differences in AUC0-24/MIC ratios were also determined using the paired t-test and the Wilcoxon signed-rank test. The level of significance for all analyses was p < 0.05.

RESULTS

Broth microdilution and E-test MICs were within +/- 1 log2 dilution for 94%, 93%, 61%, and 35% of the isolates for levofloxacin, gatifloxacin, moxifloxacin, and gemifloxacin, respectively. Broth microdilution MICs were significantly lower than E-test MICs for all 4 agents (p < 0.001). However, a categorical change in susceptibility was seen for only 1 isolate with gatifloxacin and moxifloxacin (intermediate by broth microdilution, resistant by E-test). AUC0-24/MIC ratios were significantly higher for each regimen when MICs were determined by broth microdilution compared with E-test (p < 0.001).

CONCLUSIONS

There is a significant difference in the activity of the newer fluoroquinolones against S. pneumoniae when MICs are determined by broth microdilution and E-test. When evaluating fluoroquinolone activity and pharmacodynamics against this organism, clinicians must be aware that MIC testing methodology may have a significant impact on the results.

Pharmacokinetics and pharmacodynamics of fluoroquinolones

The pharmacokinetic characteristics of levofloxacin, moxifloxacin, and gatifloxacin include excellent oral bioavailability (90-99%), extensive penetration into tissues and body fluids, and an elimination half-life (6-12 hrs) that allows for once-daily dosing in patients with normal renal function. Levofloxacin and gatifloxacin primarily are excreted unchanged in the urine, whereas moxifloxacin undergoes hepatic metabolism. The pharmacodynamic values that correlate with successful clinical and microbiologic outcomes, as well as prevent emergence of bacterial resistance, are ratios of maximum or peak unbound drug concentration (Cmax) to minimum inhibitory concentration (MIC), and 24-hour unbound area under the concentration curve (AUC(0-24hr)) to MIC. For gram-negative infections, a Cmax:MIC greater than or equal to 10 and AUC(0-24hr):MIC greater than or equal to 125 are associated with increased probability of a successful outcome. For infections caused by Streptococcus pneumoniae, an AUC(0-24hr):MIC of 30 or more is suggested for favorable clinical outcomes. Pharmacokinetic and pharmacodynamic values influence rational therapeutic decisions in the selection and dosages of these drugs.

Fluoroquinolone susceptibility, resistance, and pharmacodynamics versus clinical isolates of Streptococcus pneumoniae from Indiana

The in vitro activity and pharmacodynamics (AUC(0-24)/MIC) of levofloxacin, gatifloxacin, moxifloxacin, and gemifloxacin were evaluated against 307 clinical isolates of Streptococcus pneumoniae from Indianapolis, Indiana. Organisms were collected between January 1999 and April 2000, and MICs were determined by broth microdilution. Serum concentration-time profiles were simulated for the following oral regimens administered once daily: levofloxacin 500 mg and 750 mg; gatifloxacin 400 mg; moxifloxacin 400 mg; gemifloxacin 320 mg. Free 24 h area under the serum concentration-time curves (AUC(0-24)) were calculated, and the average AUC(0-24)/MIC was calculated for each regimen. Differences in AUC(0-24)/MIC among agents were determined by analysis of variance (Scheffe post-hoc test, p < 0.05). Overall, gemifloxacin was the most potent agent tested. Five (1.7%), 4 (1.3%), and 2 (0.7%) isolates were resistant to levofloxacin, gatifloxacin, and moxifloxacin, respectively. None of the isolates was resistant to gemifloxacin. Gemifloxacin AUC(0-24)/MIC was significantly greater than all other regimens (p < 0.0001), with the exception of moxifloxacin. However, the percent of isolates for which an AUC(0-24)/MIC >or= 30-50 can be achieved is similar for gemifloxacin, moxifloxacin, gatifloxacin, and levofloxacin 750 mg. Large comparative studies are needed to determine if the differences in AUC(0-24)/MIC among fluoroquinolones are clinically significant.

Comparative in vitro activity and pharmacodynamics of five fluoroquinolones against clinical isolates of Streptococcus pneumoniae

STUDY OBJECTIVE

To compare in vitro activity and pharmacodynamics of five fluoroquinolones against clinical isolates of Streptococcus pneumoniae.

DESIGN

In vitro analysis.

SETTING

University research laboratory.

INTERVENTION

Minimum inhibitory concentrations (MICs) were determined for penicillin and five fluoroquinolones by E test for 201 S. pneumoniae isolates. Serum concentration-time profiles were simulated for the following regimens: ciprofloxacin 750 mg orally every 12 hours and 400 mg intravenously every 8 hours; levofloxacin 500 mg orally and intravenously every 24 hours; trovafloxacin 200 mg orally and intravenously every 24 hours; gatifloxacin 400 mg orally and intravenously every 24 hours; and clinafloxacin 200 mg orally and intravenously every 12 hours.

MEASUREMENTS AND MAIN RESULTS

Free 24-hour areas under the serum concentration-time curves (AUC0-24) were calculated using the trapezoidal rule, and the average AUC0-24:MIC ratio was calculated for each regimen. Differences in ratios among agents were determined by analysis of variance (Scheffe post hoc test, p < 0.05). For intravenous dosing, the average AUC0-24:MIC for gatifloxacin, clinafloxacin, trovafloxacin, ciprofloxacin, and levofloxacin was 146, 142, 122, 71, and 61, respectively. For both oral and intravenous regimens, gatifloxacin and clinafloxacin ratios were significantly greater than those for trovafloxacin, levofloxacin, and ciprofloxacin (p < or = 0.007). Ratios for trovafloxacin were significantly greater than those for levofloxacin and ciprofloxacin (p < 0.0001), and levofloxacin and ciprofloxacin ratios were not significantly different from each other.

CONCLUSION

Gatifloxacin and clinafloxacin achieve significantly higher AUC0-24:MIC ratios for S. pneumoniae than trovafloxacin, levofloxacin, and ciprofloxacin. Large comparative studies are necessary to determine the clinical significance of these findings.

Clinical pharmacology of gatifloxacin, a new fluoroquinolone

Gatifloxacin is an advanced-generation, 8-methoxy fluoroquinolone that is active against a broad spectrum of pathogens, including antibiotic-resistant Streptococcus pneumoniae. The drug has high oral bioavailability (96%), and, therefore, oral and intravenous formulations are bioequivalent and interchangeable. Gatifloxacin has a large volume of distribution ( approximately 1.8 L/kg), low protein binding ( approximately 20%), and broad tissue distribution and is primarily excreted unchanged in the urine (>80%). Gatifloxacin can be administered without dose modification in patients with hepatic impairment, in women, and in the elderly. In vitro experiments and clinical studies indicate that gatifloxacin does not interact with drugs metabolized by the cytochrome P450 enzyme family. At therapeutically relevant doses, gatifloxacin's pharmacodynamically linked parameters (the ratio of maximum serum concentration to minimum inhibitory concentration and the ratio of the area under the curve to minimum inhibitory concentration) are similar to or better than those of other fluoroquinolones. Clinical studies show that gatifloxacin has limited potential to prolong the QT interval on the electrocardiogram and lacks the potential to cause photosensitivity reactions, to alter oral glucose tolerance, or to cause crystalluria.

Safety and pharmacokinetics of a single oral dose of gatifloxacin in patients with moderate to severe hepatic impairment

STUDY OBJECTIVES

To assess the safety and pharmacokinetics of oral gatifloxacin 400 mg in subjects with and without hepatic impairment, and the need to modify doses in patients with hepatic dysfunction.

DESIGN

Single-dose, nonrandomized, open-label, parallel-group study.

SETTING

Clinical Research Center, New Orleans, Louisiana.

PATIENTS

Eight subjects with grade B or C hepatic dysfunction (Child-Pugh classification) and eight age-, weight-, and gender-matched subjects with normal hepatic function.

INTERVENTIONS

After a single oral dose of gatifloxacin 400 mg, blood and urine samples were collected at specified times or intervals over 48 hours to determine drug concentrations.

MEASUREMENTS AND MAIN RESULTS

All 16 subjects (7 with grade B and 1 with grade C hepatic impairment, 8 with normal hepatic function) completed the study. Peak plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC0-infinity) for gatifloxacin were 32% and 22% higher, respectively, in subjects with hepatic impairment. Except for Cmax, the ratio of means for AUC satisfied the specified criterion (0.67-1.50) for lack of effect. There were no statistically significant differences in any other pharmacokinetic values except apparent oral clearance (ClT/F). All treatment-emergent adverse events were mild or moderate in intensity and resolved before subjects were discharged from the study.

CONCLUSION

Modest increases in Cmax and AUC0-infinity are not anticipated to have a negative effect on the outcome of therapy in hepatically impaired subjects, nor are they anticipated to result in adverse drug reactions. Patients with moderate to severe (Child-Pugh grade B or C) hepatic dysfunction do not require gatifloxacin dose adjustments. In addition, the similarity in half-life (t1/2) for the groups (8.9 hrs for hepatically impaired subjects, 9.3 hrs for controls) suggests that no difference would be anticipated in the extent of drug accumulation after multiple doses. The overall safety and tolerability of a single oral dose of gatifloxacin 400 mg were excellent in both healthy subjects and those with hepatic impairment.

Age and gender effects on the pharmacokinetics of gatifloxacin

STUDY OBJECTIVE

To compare the pharmacokinetics and safety of gatifloxacin in elderly (> or = 65 yrs) and young (18-45 yrs) men and women.

DESIGN

Open-label, parallel-group, single-dose study.

SETTING

GFI Pharmaceutical Services Inc., Evansville, Indiana, USA.

SUBJECTS

Forty-eight healthy subjects in four groups of 12 each.

INTERVENTIONS

Subjects received single oral doses of gatifloxacin 400 mg. Serial blood and urine samples were collected for 96 hours after dosing to determine drug concentrations.

MEASUREMENTS AND MAIN RESULTS

Age and gender had moderate effects on the pharmacokinetics of gatifloxacin. Elderly women had a 21% higher geometric mean peak plasma concentration (Cmax) and a 32% higher area under the plasma concentration-time curve (AUC0-infinity) than young women. Adjustment for creatinine clearance had only a slight effect on Cmax but reduced the estimated effect of age on AUC0-infinity in women from a 32% increase to a 15% increase. Gender effects on pharmacokinetic values were noted among elderly subjects only. Geometric means for Cmax and AUC0-infinity were 21% and 33% higher, respectively, for elderly women and elderly men. Adjustment for body weight reduced these differences to 11% and 20%, respectively.

CONCLUSION

The effects of age on gatifloxacin pharmacokinetic values were largely attributed to declining renal function, whereas those of gender were largely attributed to differences in body weight. These modest age- and gender-related differences do not warrant dosage adjustment.