Levofloxacin. A review of its antibacterial activity, pharmacokinetics and therapeutic efficacy

Disposition kinetics and dosage regimen of levofloxacin on concomitant administration with paracetamol in crossbred calves

The disposition kinetics of levofloxacin was investigated in six male crossbred calves following single intravenous administration, at a dose of 4 mg/kg body weight, into the jugular vein subsequent to a single intramuscular injection of paracetamol (50 mg/kg). At 1 min after the injection of levofloxacin, the concentration of levofloxacin in plasma was 17.2 ± 0.36 µg/ml, which rapidly declined to 6.39 ± 0.16 µg/ml at 10 min. The drug level above the MIC₉₀ in plasma, was detected for up to 10 h. Levofloxacin was rapidly distributed from blood to the tissue compartment as evidenced by the high values of the distribution coefficient, α (17.3 ± 1.65 /h) and the ratio of K₁₂/K₂₁ (1.83 ± 0.12). The values of AUC and Vd_area were 12.7 ± 0.12 µg.h/ml and 0.63 ± 0.01 l/kg. The high ratio of the AUC/MIC (126.9 ± 1.18) obtained in this study indicated the excellent antibacterial activity of levofloxacin in calves. The elimination half-life, MRT and total body clearance were 1.38 ± 0.01 h, 1.88 ± 0.01 h and 0.32 ± 0.003 l/kg/h, respectively. Based on the pharmacokinetic parameters, an appropriate intravenous dosage regimen for levofloxacin would be 5 mg/kg repeated at 24 h intervals when prescribed with paracetamol in calves.

Levofloxacin in the treatment of complicated urinary tract infections and acute pyelonephritis

Levofloxacin is a widely used fluoroquinolone approved for the treatment of complicated urinary tract infections and acute pyelonephritis. A comprehensive review of the medical literature identified five publications evaluating levofloxacin for the treatment of either complicated urinary tract infections or acute pyelonephritis. All trials, although variable in their inclusion criteria and levofloxacin dosing strategies, reported microbiologic, clinical, and safety-related outcomes. High microbiologic eradication rates, ranging from 79.8% to 95.3%, were observed in all studies. Escherichia coli was the most commonly isolated uropathogen. Data on levofloxacin resistance, both at baseline and after therapy, were limited. Clinical success was observed to range from 82.6% to 93% when measured after the completion of therapy. These clinical and microbiologic results were comparable to the fluoroquinolone comparators in all trials. Insufficient data are available to evaluate the outcomes in any meaningful patient subgroups, including catheterized patients, and those with other specific complicating factors. Levofloxacin was well tolerated in these studies, with headache, gastrointenstinal effects, and dizziness being the most commonly reported adverse events. The published data support the use of levofloxacin in complicated urinary tract infections and acute pyelonephritis. Further trials are necessary to evaluate levofloxacin within specific patient sub-populations.

Disposition kinetics and urinary excretion of levofloxacin on concomitant administration with meloxicam in cross-bred calves

The disposition kinetics and urinary excretion study of levofloxacin was conducted in 5 male cross-bred calves following its single intravenous administration (4mgkg(-1)) concurrently with meloxicam (0.5mgkg(-1)). Levofloxacin was estimated by microbiological assay. The drug levels above MIC(90) in plasma, were detected up to 10h. Disposition kinetic parameters were calculated by two-compartment open model. Rapid distribution of levofloxacin was evidenced by a small distribution half-life (0.13±0.01h) and high K(12)/K(21) ratio (2.21±0.15). High ratio of AUC/MIC (90.2±3.41) indicated good antibacterial activity of levofloxacin. The AUC, Vd(area), elimination half-life, MRT and total body clearance were 9.02±0.34μgml(-1)h, 1.38±0.05lkg(-)1, 2.16±0.08h, 2.58±0.11h and 0.45±0.02lkg(-1)h(-1), respectively. About 38.4% of the administered dose of levofloxacin was excreted in urine within 24h. A suitable intravenous dosage regimen for levofloxacin would be 1.8mgkg(-1) repeated at 8h intervals when prescribed with meloxicam in calves.

Lipids changes in liver cancer

Liver is one of the most important organs in energy metabolism. Most plasma apolipoproteins and endogenous lipids and lipoproteins are synthesized in the liver. It depends on the integrity of liver cellular function, which ensures homeostasis of lipid and lipoprotein metabolism. When liver cancer occurs, these processes are impaired and the plasma lipid and lipoprotein patterns may be changed. Liver cancer is the fifth common malignant tumor worldwide, and is closely related to the infections of hepatitis B virus (HBV) and hepatitis C virus (HCV). HBV and HCV infections are quite common in China and other Southeast Asian countries. In addition, liver cancer is often followed by a procession of chronic hepatitis or cirrhosis, so that hepatic function is damaged obviously on these bases, which may significantly influence lipid and lipoprotein metabolism in vivo. In this review we summarize the clinical significance of lipid and lipoprotein metabolism under liver cancer.

Metabolism of high density lipoproteins in liver cancer

Liver plays a vital role in the production and catabolism of plasma lipoproteins. It depends on the integrity of cellular function of liver, which ensures homeostasis of lipid and lipoprotein metabolism. When liver cancer occurs these processes are impaired and high-density lipoproteins are changed.

Proarrhythmia as a Class Effect of Quinolones: Increased Dispersion of Repolarization and Triangulation of Action Potential Predict Torsades de Pointes

BACKGROUND

Numerous noncardiovascular drugs prolong repolarization and thereby increase the risk for patients to develop life-threatening tachyarrhythmias of the torsade de pointes (TdP) type. The development of TdP is an individual, patient-specific response to a repolarization-prolonging drug, depending on the repolarization reserve. The aim of the present study was to analyze the underlying mechanisms that discriminate hearts that will develop TdP from hearts that will not develop TdP. We therefore investigated the group of quinolone antibiotics that reduce repolarization reserve via I(Kr) blockade in an intact heart model of proarrhythmia.

METHODS AND RESULTS

In 47 Langendorff-perfused, AV-blocked rabbit hearts, ciprofloxacin (n = 10), ofloxacin (n = 14), levofloxacin (n = 10), and moxifloxacin (n = 13) in concentrations from 100 microM to 1,000 microM were infused. Eight monophasic action potentials (MAPs) and an ECG were recorded simultaneously. After incremental pacing at cycle lengths from 900 ms to 300 ms to compare the action potential duration, potassium concentration was lowered to provoke TdP. All antibiotics led to a significant increase in QT interval and MAP duration, and exhibited reverse-use dependence. Eight simultaneously recorded MAPs demonstrated an increase in dispersion of repolarization in the presence of all antibiotics. MAP triangulation (ratio: MAP(90/50)) and fluctuation of consecutive action potentials were increased for all tested drugs at high concentrations. In the presence of low potassium concentration, all quinolones led to TdP: ciprofloxacin, 4 out of 10 (40%); ofloxacin, 3 out of 14 (21%); moxifloxacin, 9 out of 13 (69%); and levofloxacin, 2 out of 10 (20%). Hearts that developed TdP demonstrated a significant greater influence on dispersion of repolarization and on triangulation as compared with hearts without TdP.

CONCLUSION

Quinolone antibiotics may be proarrhythmic due to a significant effect on myocardial repolarization. The individual response of a heart to develop TdP in this experimental model is characterized by a greater effect on dispersion of repolarization and on triangulation of action potential as compared with hearts that do not develop TdP.

Penetration of topically applied levofloxacin into eyes with thin-wall filtering bleb after trabeculectomy

PURPOSE

To investigate the comparative penetration of 0.3% levofloxacin eye drops into the aqueous humour between cataract patients with or without (control) thin-wall filtering blebs.

METHODS

One drop of 0.3% levofloxacin was administered to the eyes at 30-min intervals for 3.5 h before phacoemulcification for both groups. Aqueous humour samples (0.1-0.2 ml) were aspirated during surgery. The concentration of levofloxacin in the aqueous humour was determined by high-performance liquid chromatography. The Student's t-test, Pearson correlation, and chi(2) test were used to compare the data of the two groups. A P<0.05 was required for results to be considered statistically significant.

RESULTS

The levofloxacin concentration in the aqueous humour was significantly increased (P<0.0001) in the bleb (mean+SD: 3.7+/-2.3 microg/ml) vscontrol group (0.4+/-0.2 microg/ml). Intraocular pressure and the bleb area were not correlated with levofloxacin concentration.

CONCLUSION

The presence of thin-wall filtering blebs increases intraocular penetration of topically administered levofloxacin.

Pharmacokinetics, urinary excretion and dosage regimen of levofloxacin following a single intramuscular administration in cross bred calves

The pharmacokinetics and urinary excretion following single intramuscular administration of levofloxacin at a dose of 4 mg/kg was investigated in seven male cross bred calves. Appreciable plasma concentration of levofloxacin (0.38+/-0.06 microgram/ml) was detected at 1 min after injection and the peak plasma level of 3.07+/-0.08 microgram/ml was observed at 1 h. The drug level above MIC90 in plasma was detected up to 12 h after administration. Rapid absorption of the drug was also evident by the high value of the absorption rate constant (2.14+/-0.24 /h). The overall systemic bioavailability of levofloxacin, after intramuscular administration, was 56.6+/-12.4%. The high value of AUC (7.66+/-0.72 mg.h/ml) reflected the vast area of body covered by drug concentration. Extensive distribution of the drug into various body fluids and tissues was noted by the high value of Vd(area) (1.02+/-0.05 l/kg). The high ratio of AUC/MIC (76.6+/-7.25) obtained in this study indicated excellent clinical and bacteriological efficacy of levofloxacin in calves. The elimination half-life and MRT were 3.67+/-0.4 h and 5.57+/-0.51 h, respectively. The total body clearance (Cl(B)) was 204.9+/-22.6 ml/kg/h. On the basis of the pharmacokinetic parameters, a suitable intramuscular dosage regimen for levofloxacin in calves would be 1.5 mg/kg repeated at 12 h intervals.

Levofloxacin for the treatment of community-acquired pneumonia

New respiratory fluoroquinolones (FQs), such as levofloxacin, offer many improved qualities over older agents, such as ciprofloxacin. These include retaining excellent Gram-negative bacilli activity, with improved Gram-positive activity. New FQ-like levofloxacin possesses greater bioavailabilty and a longer serum half-life compared with ciprofloxacin, allowing for once-daily dosing, which may improve patient adherence. The high bioavailability of levofloxacin allows for rapid step-down from intravenous administration to oral therapy, minimizing unnecessary hospitalization, which may decrease costs and improve patient quality of life. Levofloxacin has been evaluated for the treatment of community-acquired pneumonia (CAP) in numerous randomized clinical trials. Most published studies have used the 500 mg dose, although more recent studies have investigated the 750 mg dose once daily. These trials demonstrate that levofloxacin is effective and safe for the treatment of CAP, displaying relatively mild adverse effects that are more or less comparable with ciprofloxacin. Levofloxacin has much to offer in terms of bacterial eradication, including for resistant respiratory pathogens. However, ciprofloxacin-resistant organisms are becoming more prevalent so prudence must be exercised when prescribing this agent.

Antimicrobial safety: focus on fluoroquinolones

BACKGROUND/PURPOSE

Infrequent toxicities associated with certain drugs and drug classes have recently gained much attention from different health-care perspectives. To protect the patient, continued surveillance of safety and tolerability data is essential. Data from preclinical testing, phase 1-3 trials, and postmarketing surveillance may be used to objectively assess the risks associated with a specific drug or family of compounds. This review summarizes safety and tolerability data for the quinolones.

MAIN FINDINGS

The most common adverse events associated with the quinolone class involve the gastrointestinal tract (nausea and diarrhea) and central nervous system (CNS) (headache and dizziness). These adverse events are usually mild and do not require discontinuation of therapy. Uncommon and potentially serious quinolone-related adverse events involve the cardiovascular system (rate-corrected electrocardiographic QT interval prolongation), musculoskeletal system (tendinitis and tendon rupture), endocrine system (glucose homeostasis dysregulation), renal system (crystalluria, interstitial nephritis, and acute renal failure), and the CNS (seizures). Severe idiosyncratic adverse events are specific to individual agents that may share some structural congruity, such as the 1-(2,4)-difluorophenyl group shared by trovafloxacin (associated with hepatitis), temafloxacin (associated with hemolytic-uremic syndrome), and tosufloxacin (associated with eosinophilic pneumonitis). Overall, discontinuation rates from clinical trials were <4% for the currently marketed quinolones. Quinolones with higher discontinuation rates, such as trovafloxacin (7.0%) and grepafloxacin (6.4%), are no longer available for general use.

CONCLUSIONS

The currently marketed quinolones are well tolerated, with safety profiles similar to those of other antimicrobial classes. Although adverse effects are unusual, some, including tendinitis and CNS-related effects, are more common with quinolones than with other antimicrobial classes. Rare adverse effects attributed to some members of the quinolone family (e.g., Torsades de Pointes, hepatotoxicity, and dysglycemias) are more likely to occur in select "susceptible" populations. These adverse events can often be circumvented by avoiding exposure to the specific quinolone. In some cases, the therapeutic value offered by a quinolone may outweigh its potential risks.

Pharmacokinetic interaction between levofloxacin and ciclosporin or tacrolimus in kidney transplant recipients: ciclosporin, tacrolimus and levofloxacin in renal transplantation

BACKGROUND AND OBJECTIVE

Bacterial infections are common complications after organ transplantation. Fluoroquinolones are frequently used for treatment because of their broad spectrum of activity; but some of them, such as ciprofloxacin and norfloxacin, are reported to increase blood concentration of ciclosporin because they are metabolised by the liver through the same enzymatic pathway, the cytochrome P450 system. This study was performed to establish whether levofloxacin, a more recent fluoroquinolone that undergoes limited hepatic metabolism, interferes with metabolism and excretion of either ciclosporin microemulsion or tacrolimus.

METHODS

Pharmacokinetic studies were carried out in two groups of renal transplant patients, on either ciclosporin or tacrolimus treatment, before and at the sixth day of treatment with levofloxacin.

RESULTS

Levofloxacin significantly increased the mean area under the blood concentration-time curve (AUC) and the other pharmacokinetic parameters of ciclosporin and tacrolimus by about 25%. The interference of levofloxacin on the hepatic metabolism of these drugs was demonstrated by the concomitant decrease by 5% of polyclonal ciclosporin concentration, which is the expression of parent drug and its metabolites. Both before and during levofloxacin treatment we observed trough concentrations of monoclonal and polyclonal ciclosporin significantly lower in the evening (C(12)) than in the morning (C(0)); this observation suggests a circadian variation in the metabolism of this drug. However, no difference between C(0) and C(12) was observed with tacrolimus, confirming its more predictable bioavailability.

CONCLUSION

Our data demonstrate that levofloxacin partially inhibits the metabolism of both ciclosporin microemulsion and tacrolimus, and therefore close therapeutic monitoring of these two drugs should be recommended during levofloxacin therapy.

Effect of ethanol on fluoroquinolone efficacy in a rat model of pneumococcal pneumonia

This investigation compared the effect of ethanol on fluoroquinolone antibiotic efficacy and pharmacodynamics in an ethanol-fed rat model of pneumococcal pneumonia. Male Sprague-Dawley rats received a liquid diet containing 36% of total calories as ethanol. Paired controls (pair-fed controls) were fed a liquid diet without ethanol or received rat chow. Diets began 7 days before and continued for 10 days after transtracheal infections with 10 times the 50% lethal dose of type 3 Streptococcus pneumoniae. Beginning 18 h after infection, the rats received once daily subcutaneous phosphate-buffered saline, levofloxacin, moxifloxacin, or trovafloxacin at 50 or 100 mg/kg of body weight. White blood cell counts were determined, blood samples were collected for culture, and mortality was recorded. Additional rats were killed on day 5 for pharmacodynamic studies and quantitative cultures of bronchoalveolar lavage fluid. Bacteremia occurred by day 3 in 20 of 22 untreated rats. All 22 untreated rats died by day 9. Moxifloxacin treatment was effective in all diet groups at both the 50- and 100-mg/kg doses. In contrast, 50-mg/kg doses of levofloxacin and trovafloxacin improved survival in ethanol-fed rats but were ineffective in chow-fed rats. High-dose trovafloxacin at 100 mg/kg was associated with increased mortality in pair-fed rats. The free-fraction area under the concentration-time curve/MIC ratio exceeded 50 with all antibiotics in the ethanol group but dropped below 30 with levofloxacin and trovafloxacin in the pair- and chow-fed rats, with higher mortality. Achievement of adequate antibiotic-free fraction area under the concentration-time curve/MIC ratios helps overcome ethanol-induced immune defects induced in experimental pneumococcal pneumonia.

In vitro activity of levofloxacin against Helicobacter pylori isolates from patients after treatment failure

We tested the in vitro activity of levofloxacin (LEV), amoxicillin (AMP), clarithromycin (CLA), metronidazole (MET), and tetracycline (TET) against 70 clinical isolates of Helicobacter pylori recovered from 70 dyspeptic patients. All patients had previously failed 2 treatment regimens: first-line triple therapy with omeprazole, AMP, and CLA, and second-line quadruple therapy with omeprazole, MET, TET, and bismuth. Resistance to CLA, MET, and LEV was found in 65.7%, 57.1%, and 18.6% of isolates, respectively. Resistance to both CLA and MET was found in 32.8%, and to CLA, MET, and LEV in 12.8%. Only 4 of the isolates were resistant to both CLA and LEV, and none was resistant to LEV alone or to MET and LEV. Physicians should consider triple therapy with omeprazole, LEV, and AMP in patients unsuccessfully treated with first- and second-line regimens.

Effect of formulation factors on in vitro permeation of moxifloxacin from aqueous drops through excised goat, sheep, and buffalo corneas

The purpose of this investigation was to evaluate the effect of formulation factors on in vitro permeation of moxifloxacin from aqueous drop through freshly excised goat, sheep, and buffalo corneas. Aqueous isotonic ophthalmic solutions of moxifloxacin hydrochloride of different concentrations (pH 7.2) or 0.5% (wt/vol) solutions of different pH or 0.5% solutions (pH 7.2) containing different preservatives were made. Permeation characteristics of drug were evaluated by putting 1 mL formulation on freshly excised cornea (0.50 cm(2)) fixed between donor and receptor compartments of an all-glass modified Franz diffusion cell and measuring the drug permeated in the receptor (containing 10 mL bicarbonate ringer at 37 degrees C under stirring) by spectrophotometry at 291 nm, after 120 minutes. Statistical analysis was done by one-way analysis of variance (ANOVA) followed by Dunnett's test. Increase in drug concentration in the formulation resulted in an increase in the quantity permeated but a decrease in percentage permeation. Increase in pH of the solution from 5.5 to 7.2 increased drug permeation, indicating pH-dependent transport. Compared with control formulation, moxifloxacin 0.5% (wt/vol) solution (pH 7.2) containing disodium edetate (EDTA) (0.01% wt/vol) produced significantly (P < .05) higher permeation with all the corneas. Formulation with benzyl alcohol significantly (P < .05) increased permeation with buffalo cornea compared with its control. Presence of benzalkonium chloride (BAK) (0.01% wt/vol) and EDTA (0.01% wt/vol) in the formulation increased permeation to the maximum with all the corneas. The results suggest that moxifloxacin 0.5% ophthalmic solution (pH 7.2) containing BAK (0.01%) and EDTA (0.01%) provides increased in vitro ocular availability through goat, sheep, and buffalo corneas.

[Levofloxacin in the treatment of acute and bacteriologically documented sinusitis with high risk of complications]

OBJECTIVES

The authors had for aim to evaluate the efficacy and tolerance of oral levofloxacin (500 mg once a day during ten days), as a treatment for acute bacterial sinusitis at risk for complications in adult patients.

PATIENTS AND METHODS

This was a prospective, multicenter, open, non-comparative, efficacy and tolerance study of levofloxacin in acute sinusitis at risk for complications, radiologically confirmed, and with documentation of the bacterial origin by fiberoptic rhinoscopy.

RESULTS

Two hundred and thirty-one patients were included and 174 patients had an X ray confirmed sinusitis. The localization was frontal in 81% patients, sphenoidal in 9.2%, ethmoidosphenoidal in 2.3%, and 7.5% patients had a pansinusitis. One hundred and thirty-three patients had a probable or proven bacterial infection, involving: Streptococcus pneumoniae (26.0%), enterobacteriaceae (19.7%), Haemophilus influenzae (17.3%), Staphylococcus aureus (15.0%), streptococci other than S. pneumoniae (7.9%), and Branhamella catarrhalis (5.5%). One hundred and one patients constituted the per protocol population. Clinical success was observed in 94.1 % patients (95/101), and 85.1% (86/101), respectively 7 to 14 days and three to four weeks after the end of treatment, with consistent success rates according to the localization of the infection, and the various pathogens involved. The tolerance data was as expected for levofloxacin.

CONCLUSIONS

The results of this study show that levofloxacin, (one 500 mg tablet QD during ten days) is efficient in over 94% patients with bacteriologically documented sinusitis at risk for complications.

Comparison of Levofloxacin and Cefotaxime Combined With Ofloxacin for ICU Patients With Community-Acquired Pneumonia Who Do Not Require Vasopressors

STUDY OBJECTIVES

To evaluate the efficacy and tolerability of levofloxacin (L) as monotherapy in patients with severe community-acquired pneumonia (CAP) in comparison with therapy using a combination of cefotaxime (C) plus ofloxacin (O).

DESIGN

Prospective, randomized 1:1, comparative, open, parallel-group study.

SETTING

Multinational study with 149 sites.

PATIENTS

A total of 398 randomized patients who had been admitted to the ICU with severe CAP without shock, including 308 patients in a modified intent-to-treat population and 271 patients in the per-protocol (PP) population (L group, 139 patients; C + O group, 132 patients).

INTERVENTIONS

Therapy with levofloxacin (500 mg IV, q12h) vs therapy with a C + O combination (C, 1g IV, q8h; O, 200 mg IV, q12h) for 10 to 14 days.

MEASUREMENTS AND RESULTS

The main end point was the clinical efficacy at the end of treatment (ie, the test-of-cure [TOC] visit). The statistical hypothesis was the noninferiority of L therapy to C + O therapy with a 2.5% alpha risk (unilateral) and a 15% maximum set difference. At the TOC visit, a clinical success was observed in 79.1% of patients (L group) and 79.5% of patients (C + O group) in the PP population (difference, -0.4%; 95% confidence interval [CI], -10.79 to 9.97% without adjustment for simplified acute physiology score [SAPS] II at inclusion; difference, -0.3%; 95% CI, -10.13 to 9.58% with adjustment for SAPS II). A satisfactory bacteriologic response was present in 73.7% of L group patients and 77.5% of C + O group patients, including responses of 75.7% and 70.3%, respectively, in the L group and C + O group in the Streptococcus pneumoniae-documented population. In the safety analysis, 20 patients in the L group (10.3%) and 16 patients in the C + O group (8.0%) experienced at least one adverse event that was considered to be treatment-related.

CONCLUSION

L therapy was at least as effective as the combination therapy of C + O in the treatment of a subset of patients with CAP requiring ICU admission. This conclusion cannot be extrapolated to patients requiring mechanical ventilation or vasopressors (ie, those patients in shock).

In vitro Activity of Levofloxacin against Recent Gram-Negative Nosocomial Pathogens

The objective of our study was to evaluate the in vitro activity of levofloxacin in comparison with other antibiotics (coamoxiclav, ceftriaxone, ceftazidime, meropenem, aztreonam, ciprofloxacin and netilmicin) against about 500 Gram-negative nosocomial microorganisms, isolated during 2003. The bactericidal activities (minimal bactericidal activity and killing curve) of levofloxacin and the other antibiotics were also evaluated. The results confirm the excellent in vitro activity of levofloxacin against multiresistant nosocomial Gram-negative pathogens, including the 73 extended spectrum beta-lactamase producer strains (90% of Escherichia coli, Enterobacter cloacae and Klebsiella pneumoniae were inhibited at 0.5 mg/l). Of particular interest is its susceptibility and bactericidal activity against Stenotrophomonas maltophilia strains. In conclusion, due to the favorable pharmacokinetics and pharmacodynamics of the molecule, associated with its safety, levofloxacin may represent a valid therapeutic option in the treatment of severe Gram-negative nosocomial infections.

Pharmacokinetics and intrapulmonary diffusion of levofloxacin in critically ill patients with severe community-acquired pneumonia

OBJECTIVE

To determine the steady-state plasma and epithelial lining fluid concentrations of intravenous levofloxacin, 500 mg, administered once or twice daily in critically ill patients with severe community-acquired pneumonia.

DESIGN

Prospective, open-label study.

SETTING

An intensive care unit and a clinical pharmacokinetic laboratory in two university hospitals.

PATIENTS

Twenty-four adult patients with severe community-acquired pneumonia and receiving mechanical ventilation were enrolled.

INTERVENTIONS

All subjects received 1-hr intravenous infusions of 500 mg levofloxacin once or twice daily. The plasma and epithelial lining fluid levofloxacin concentrations were determined at steady-state after 2 days of therapy with high-performance liquid chromatography.

MEASUREMENTS AND MAIN RESULTS

The median (interquartile range [IQR]) plasma and epithelial lining fluid peak levofloxacin concentrations were 12.6 (IQR, 12.0-14.1) and 11.9 (IQR, 8.7-13.7) mg/L, respectively, in the once-daily group and 19.7 (IQR, 19.0-22.0) and 17.8 (IQR, 16.2-23.5) mg/L in the twice-daily group, showing a pulmonary percentage penetration of >100% in both groups. The median (IQR) total body exposures were 151 (IQR, 137-174) and 416 (IQR, 406-472) mg.hr/L, respectively, in the once-daily and twice-daily groups.

CONCLUSIONS

Our results suggest that in critically ill patients who are receiving mechanical ventilation and have severe community-acquired pneumonia and creatinine clearance of >40 mL/min, the administration of 500 mg of intravenous levofloxacin once and twice daily allows for the exceeding of pharmacodynamic thresholds predictive of outcome (i.e., peak concentration to minimum inhibitory concentration ratio of >10 or area under concentration-time curve to minimal inhibitory concentration ratio of >125 hrs) both in serum and epithelial lining fluid for pathogens with minimum inhibitory concentration values of < or =1 mg/L and >1 mg/L, respectively.

High levels of dual resistance to clarithromycin and metronidazole and in vitro activity of levofloxacin against Helicobacter pylori isolates from patients after failure of therapy

Current treatment for Helicobacter pylori infections generally includes two or more antimicrobials (amoxicillin, clarithromycin, nitroimidazoles, tetracycline, etc.), but treatment fails in 10-20% of all cases, often because of drug resistance. Levofloxacin has been proposed as an alternative for these refractory infections. We examined 67 H. pylori isolates from patients unsuccessfully treated with amoxicillin, clarithromycin, metronidazole and levofloxacin. Minimum inhibitory concentrations determined with the epsilometer test revealed clarithromycin and metronidazole resistance in 91 and 82.1% of the isolates, respectively; 52 (77.6%) were resistant to both drugs. All 67 isolates were susceptible to amoxicillin and tetracycline. Fifty-two isolates had levofloxacin MICs of 0.01-2 mg/l; the remaining 15 (22.4%), all clarithromycin- and metronidazole-resistant, had MICs >/= 8 mg/l. Levofloxacin may be an option for refractory H. pylori infections, but the choice should be based on in vitro susceptibility data, and physicians should consider local resistance patterns when treating these infections empirically.

The newer fluoroquinolones

This article discusses the newer fluoroquinolones in detail with respect to their pharmacokinetics, pharmacodynamics, safety, and spectrum of in vitro activity. The newer agents are compared and contrasted with the older ones, particularly ciprofloxacin. Efficacy of the newer fluoroquinolones when compared with antimicrobial agents in other classes is also presented in detail. Appropriate use of the newer fluoroquinolones is addressed, including their ever expanding role in the treatment of both upper and lower respiratory tract infections and skin and soft tissue infection. Available data on the use of the newer fluoroquinolones in the management of genitourinary tract infections, gastrointestinal infections, and osteomyelitis are also discussed.

Effectiveness of ciprofloxacin, levofloxacin, or moxifloxacin for treatment of experimental Staphylococcus aureus keratitis

The purpose of this study was to quantitatively compare, in a rabbit keratitis model, the levels of effectiveness of moxifloxacin, levofloxacin, and ciprofloxacin for the treatment of Staphylococcus aureus isolates of diverse antibiotic susceptibilities. Rabbit eyes were intrastromally injected with approximately 100 CFU of methicillin-sensitive or methicillin-resistant S. aureus (MSSA or MRSA, respectively) organisms that were either sensitive or resistant to ofloxacin. One drop of moxifloxacin (0.5%), levofloxacin (0.5%), or ciprofloxacin (0.3%) was topically applied hourly from 4 to 9 (early) or 10 to 15 (late) h postinfection. At 1 h after cessation of therapy, the corneas were harvested, and the number of CFU per cornea was determined. For the ofloxacin-sensitive strains, early treatment of MSSA or MRSA with moxifloxacin, levofloxacin, or ciprofloxacin produced approximately a 5-log decrease in CFU per cornea relative to that in untreated eyes (P </= 0.0001). For late therapy of ofloxacin-sensitive strains, moxifloxacin, levofloxacin, and ciprofloxacin produced approximately 5-, 4-, and 2- to 3-log reductions in CFU per cornea, respectively (P </= 0.0001). Early treatment of the ofloxacin-resistant strains with either moxifloxacin or levofloxacin produced a >/=4-log or >/=3-log decrease, respectively, in the MSSA or MRSA strains (P </= 0.0001), whereas ciprofloxacin treatment produced a 1-log decrease in CFU per cornea relative to that in untreated eyes (P = 0.1540). For late treatment of ofloxacin-resistant strains, levofloxacin and ciprofloxacin failed to significantly reduce the number of CFU per cornea (P >/= 0.3627), whereas moxifloxacin produced a significant reduction in CFU per cornea of approximately 1 log (P </= 0.0194). Therefore, for three of the four treatments tested, moxifloxacin demonstrated greater effectiveness than either levofloxacin or ciprofloxacin.

Efficacy of garenoxacin in treatment of experimental endocarditis due to Staphylococcus aureus or viridans group streptococci

The activity of garenoxacin was investigated in rats with experimental endocarditis due to staphylococci and viridans group streptococci (VGS). The staphylococci tested comprised one ciprofloxacin-susceptible and methicillin-susceptible Staphylococcus aureus (MSSA) isolate (isolate 1112), one ciprofloxacin-susceptible but methicillin-resistant S. aureus (MRSA) isolate (isolate P8), and one ciprofloxacin-resistant mutant (grlA) of P8 (isolate P8-4). The VGS tested comprised one penicillin-susceptible isolate and one penicillin-resistant isolate (Streptococcus oralis 226 and Streptococcus mitis 531, respectively). To simulate the kinetics of drugs in humans, rats were infused intravenously with garenoxacin every 24 h (peak and trough levels in serum, 6.1 and 1.0 mg/liter, respectively; area under the concentration-time curve [AUC], 63.4 mg. h/liter) or levofloxacin every 12 h (peak and trough levels in serum, 7.3 and 1.5 mg/liter, respectively; AUC, 55.6 mg. h/liter) for 3 or 5 days. Flucloxacillin, vancomycin, and ceftriaxone were used as control drugs. Garenoxacin, levofloxacin, flucloxacillin, and vancomycin sterilized >/=70% of the vegetations infected with both ciprofloxacin-susceptible staphylococcal isolates (P < 0.05 versus the results for the controls). Garenoxacin and vancomycin also sterilized 70% of the vegetations infected with ciprofloxacin-resistant MRSA isolate P8-4, whereas treatment with levofloxacin failed against this organism (cure rate, 0%; P < 0.05 versus the results obtained with the comparator drugs). Garenoxacin did not select for resistant derivatives in vivo. In contrast, levofloxacin selected for resistant variants in four of six rats infected with MRSA isolate P8-4. Garenoxacin sterilized 90% of the vegetations infected with both penicillin-susceptible and penicillin-resistant isolates of VGS. Levofloxacin sterilized only 22 and 40% of the vegetations infected with penicillin-susceptible S. oralis 226 and penicillin-resistant S. mitis 531, respectively. Ceftriaxone sterilized only 40% of those infected with penicillin-resistant S. mitis 531 (P < 0.05 versus the results obtained with garenoxacin). No quinolone-resistant VGS were detected. In all the experiments successful quinolone treatment was predicted by specific pharmacodynamic criteria (D. R. Andes and W. A. Craig, Clin. Infect. Dis. 27:47-50, 1998). The fact that the activity of garenoxacin was equal or superior to those of the standard comparators against staphylococci and VGS indicates that it is a potential alternative for the treatment of infections caused by such bacteria.

Pharmacokinetics and effects on bowel and throat microflora of oral levofloxacin as antibacterial prophylaxis in neutropenic patients with haematological malignancies

Gram-positive breakthrough infections pose a major drawback to the use of quinolones for antibacterial prophylaxis in neutropenic patients. Levofloxacin offers the advantage of an augmented Gram-positive spectrum and may potentially overcome this problem. In an open-label, clinical pilot study, we investigated the effects on throat and bowel microflora and pharmacokinetics of a once-daily oral dose of 500 mg levofloxacin, during neutropenia in 20 patients with haematological malignancies. Gram-negative bowel flora and Staphylococcus aureus were successfully eradicated. No Gram-negative infections occurred. Minimal inhibitory concentration values for viridans group (VG) streptococci tended to increase, in four patients over 8 mg/l, indicating resistance to levofloxacin. Four patients developed blood-stream infections with levofloxacin-resistant Gram-positive cocci. No significant changes in numbers of anaerobic microorganisms were observed. Pharmacokinetic parameters of levofloxacin, including the maximum serum concentration (C(max)), time to C(max) (T(max)), area under the concentration-time curve (AUC), volume of distribution at steady state (V(ss)/F) and clearance (CL/F) were not statistically different at first dose and during neutropenia. In conclusion, levofloxacin eradicates Gram-negative microorganisms and S. aureus and spares the anaerobic flora. Its pharmacokinetic profile is unaltered during neutropenia. However, prolonged administration of levofloxacin as antibacterial prophylaxis may be hampered by the emergence of levofloxacin-resistant VG streptococci.

Comparative roles of levofloxacin and ofloxacin in the treatment of multidrug-resistant tuberculosis: preliminary results of a retrospective study from Hong Kong

OBJECTIVE

To compare levofloxacin and ofloxacin in the treatment of multidrug-resistant tuberculosis (MDR-TB).

PATIENTS AND METHODS

A retrospective analysis of 106 patients with MDR-TB (February 1990 through December 2000) receiving directly observed therapy with fluoroquinolone and accompanying drugs, which mainly included aminoglycosides, cycloserine, ethionamide/prothionamide, and pyrazinamide, was performed. Clinical data from 99 suitable patients were subjected to univariate analysis, stratification, and multiple logistic regression to compare the roles of levofloxacin and ofloxacin in multidrug regimens.

RESULTS

Forty patients received 612.5 +/- 79.0 mg qd levofloxacin (mean +/- SD), and 59 patients received 628.8 +/- 101.8 mg qd ofloxacin together with similar active second-line drugs for similar durations. The times to sputum smear (both 1.8 months) and culture conversion (both 2.1 months) were equivalent. Adverse reactions occurred at similar rates (10.0% vs 11.9%). The combined treatment success rate was 83.8%, being higher among ofloxacin-susceptible than ofloxacin-resistant cases (90.5% vs 64.0%, p < 0.01). The success rates for the levofloxacin group were 90.0% (overall), 96.2% (ofloxacin-susceptible cases), and 78.6% (ofloxacin-resistant cases) in comparison with 79.7%, 87.5%, and 45.5%, respectively, for the ofloxacin group (Mantel-Haenszel common odds ratio estimate, 4.0; p < 0.05). Bacillary susceptibility to ofloxacin, good adherence, radiographic extent of one lung or less, and use of levofloxacin were independent predictors of favorable outcome (odds ratios, 7.6 to 21.3). One patient each from both groups relapsed.

CONCLUSION

Levofloxacin was found to be more efficacious than ofloxacin when incorporated into multidrug regimens used for treatment of MDR-TB.

Corneal penetration of levofloxacin into the human aqueous humour: a comparison with ciprofloxacin

PURPOSE

To compare aqueous humour levels of levofloxacin and ciprofloxacin following topical application to patients scheduled for cataract surgery.

METHODS

A total of 59 patients undergoing cataract surgery were randomly assigned to topical treatment with either levofloxacin 0.5% or ciprofloxacin 0.3% eye drops, at one drop every 15 min for four doses immediately prior to surgery. Aqueous humour samples were collected by paracentesis and analysed for drug content.

RESULTS

The (geometric) mean aqueous humour concentration of levofloxacin was 0.728 microg/ml; that of ciprofloxacin was 0.080 microg/ml.

CONCLUSIONS

Levofloxacin achieves 9.1 times the aqueous humour concentration of ciprofloxacin. It could be considered a better choice than ofloxacin or ciprofloxacin for topical ophthalmic use.

The expanding role of fluoroquinolones

There has been a growing rate of resistance among common urinary tract pathogens, such as Escherichia coli, to traditional antimicrobial therapies including the "gold standard" trimethoprim-sulfamethoxazole (TMP-SMX). Consequently, fluoroquinolone antimicrobial agents have taken on an expanding management role for UTIs. In fact, the recent Infectious Diseases Society of America clinical management guidelines for UTI recommend fluoroquinolones as first-line therapy for uncomplicated UTI in areas where resistance is likely to be of concern. Fluoroquinolones have demonstrated high bacteriologic and clinical cure rates, as well as low rates of resistance, among most common uropathogens. There are currently 7 fluoroquinolones with indications for UTI in the United States. However, only 3 are commonly used: levofloxacin, ciprofloxacin, and, to a lesser extent, gatifloxacin. Many of the fluoroquinolone agents have once-daily dosing regimens, enhancing patient adherence. In addition, levofloxacin and gatifloxacin have same-dose bioequivalency between their intravenous and oral formulations, allowing for "switch" or step-down therapy from parenteral to oral formulations of the same agent at the same dose. Fluoroquinolones are indicated for the management of acute uncomplicated UTIs, as well as complicated and severe UTI and pyelonephritis, in adults. They are the first-line treatment of acute uncomplicated cystitis in patients who cannot tolerate sulfonamides or TMP, who live in geographic areas with known resistance >10% to 20% to TMP-SMX, or who have risk factors for such resistance. Fluoroquinolone properties include a broad spectrum of coverage, low rates of resistance, and good safety profiles.

[Community-acquired pneumonia: usefulness of clinical presentation in the selection of antibiotic treatment]

BACKGROUND

Our purpose was to assess the usefulness of a strategy based on the clinical presentation in order to choose antibiotics in patients with non-severe community-acquired pneumonia (CAP).

PATIENTS AND METHOD

During one year, all patients admitted to the emergency department with a diagnosis of non-severe (Fine risk-classes I, II and III) CAP, were randomized and assigned into the following groups: GROUP 1: the clinical presentation was not taken into account and all patients were treated with levofloxacin; GROUP 2: patients with typical presentation were treated with amoxicillin and patients with atypical presentation were treated with clarithromycin. The following aspects were evaluated during the follow-up: presence of fever after 72 h of treatment, days of hospitalization and complications.

RESULTS

The eventual population analyzed included 125 patients: 59 (47%) were assigned to Group 1 and 66 (53%) to Group 2. Patients assigned to Group 1 had a lower rate of fever after 72 h of treatment (7% vs 27%, p = 0.005); they were hospitalized for fewer days (4.8 vs 8.1 days, p = 0.01), and had less complications: changes in antibiotic treatment (10% vs 23% p = NS), admissions in ICU (0% vs 5%, p = NS), re-admissions in hospital (0% vs 5%, p = 0.05) and mortality (0% vs 2%, p = NS).

CONCLUSIONS

A strategy of empiric treatment of non-severe CAP with levofloxacin as the antibiotic of choice is more useful than that of a treatment based on the clinical presentation.

The expanding role of fluoroquinolones

There has been a growing rate of resistance among common urinary tract pathogens, such as Escherichia coli, to traditional antimicrobial therapies including the "gold standard" trimethoprim-sulfamethoxazole (TMP-SMX). Consequently, fluoroquinolone antimicrobial agents have taken on an expanding management role for UTIs. In fact, the recent Infectious Diseases Society of America clinical management guidelines for UTI recommend fluoroquinolones as first-line therapy for uncomplicated UTI in areas where resistance is likely to be of concern. Fluoroquinolones have demonstrated high bacteriologic and clinical cure rates, as well as low rates of resistance, among most common uropathogens. There are currently 7 fluoroquinolones with indications for UTI in the United States. However, only 3 are commonly used: levofloxacin, ciprofloxacin, and, to a lesser extent, gatifloxacin. Many of the fluoroquinolone agents have once-daily dosing regimens, enhancing patient adherence. In addition, levofloxacin and gatifloxacin have same-dose bioequivalency between their intravenous and oral formulations, allowing for "switch" or step-down therapy from parenteral to oral formulations of the same agent at the same dose. Fluoroquinolones are indicated for the management of acute uncomplicated UTIs, as well as complicated and severe UTI and pyelonephritis, in adults. They are the first-line treatment of acute uncomplicated cystitis in patients who cannot tolerate sulfonamides or TMP, who live in geographic areas with known resistance >10% to 20% to TMP-SMX, or who have risk factors for such resistance. Fluoroquinolone properties include a broad spectrum of coverage, low rates of resistance, and good safety profiles.

Vitreous penetration of levofloxacin in the uninflamed phakic human eye

AIMS

To assess the vitreous penetration of oral levofloxacin (a new fluoroquinolone antibiotic with improved Gram positive activity) in uninflamed phakic eyes.

METHODS

15 patients for macula hole surgery were recruited to the study. 10 received a single 500 mg dose of levofloxacin by mouth preoperatively. Five acted as controls. Serum and undiluted vitreous samples were obtained at surgery and analysed by HPLC.

RESULTS

Levofloxacin was detectable 2.5 hours after administration in the vitreous. A peak concentration of 1.6 microg/ml (or mg/l) was measured between 2.5 and 4 hours post-dose.

CONCLUSION

Oral levofloxacin reaches the vitreous rapidly in the uninflamed phakic eye. Levels did not reach MIC(90) for the commonest infecting organisms. Nevertheless, levofloxacin would be expected to be active against a higher proportion of infecting organisms than either ciprofloxacin or ofloxacin.

A critical review of the fluoroquinolones: focus on respiratory infections

The new fluoroquinolones (clinafloxacin, gatifloxacin, gemifloxacin, grepafloxacin, levofloxacin, moxifloxacin, sitafloxacin, sparfloxacin and trovafloxacin) offer excellent activity against Gram-negative bacilli and improved Gram-positive activity (e.g. against Streptococcus pneumoniae and Staphylococcus aureus) over ciprofloxacin. Ciprofloxacin still maintains the best in vitro activity against Pseudomonas aeruginosa. Clinafloxacin, gatifloxacin, moxifloxacin, sitafloxacin, sparfloxacin and trovafloxacin display improved activity against anaerobes (e.g. Bacteroides fragilis) versus ciprofloxacin. All of the new fluoroquinolones display excellent bioavailability and have longer serum half-lives than ciprofloxacin allowing for once daily dose administration. Clinical trials comparing the new fluoroquinolones to each other or to standard therapy have demonstrated good efficacy in a variety of community-acquired respiratory infections (e.g. pneumonia, acute exacerbations of chronic bronchitis and acute sinusitis). Limited data suggest that the new fluoroquinolones as a class may lead to better outcomes in community-acquired pneumonia and acute exacerbations of chronic bronchitis versus comparators. Several of these agents have either been withdrawn from the market, had their use severely restricted because of adverse effects (clinafloxacin because of phototoxicity and hypoglycaemia; grepafloxacin because of prolongation of the QTc and resultant torsades de pointes; sparfloxacin because of phototoxicity; and trovafloxacin because of hepatotoxicity), or were discontinued during developmental phases. The remaining fluoroquinolones such as gatifloxacin, gemifloxacin, levofloxacin and moxifloxacin have adverse effect profiles similar to ciprofloxacin. Extensive post-marketing safety surveillance data (as are available with ciprofloxacin and levofloxacin) are required for all new fluoroquinolones before safety can be definitively established. Drug interactions are limited; however, all fluoroquinolones interact with metal ion containing drugs (eg. antacids). The new fluoroquinolones (gatifloxacin, gemifloxacin, levofloxacin and moxifloxacin) offer several advantages over ciprofloxacin and are emerging as important therapeutic agents in the treatment of community-acquired respiratory infections. Their broad spectrum of activity which includes respiratory pathogens such as penicillin and macrolide resistant S. pneumoniae, favourable pharmacokinetic parameters, good bacteriological and clinical efficacy will lead to growing use of these agents in the treatment of community-acquired pneumonia, acute exacerbations of chronic bronchitis and acute sinusitis. These agents may result in cost savings especially in situations where, because of their potent broad-spectrum activity and excellent bioavailability, they may be used orally in place of intravenous antibacterials. Prudent use of the new fluoroquinolones will be required to minimise the development of resistance to these agents.

Pharmacokinetics of levofloxacin during continuous venovenous hemodiafiltration and continuous venovenous hemofiltration in critically ill patients

STUDY OBJECTIVE

To assess the pharmacokinetics of levofloxacin during continuous venovenous hemodiafiltration (CVVHDF) and continuous venovenous hemofiltration (CVVH).

DESIGN

Nonrandomized pharmacokinetic evaluation.

SETTING

University surgical intensive care unit.

PATIENTS

Six critically ill patients.

INTERVENTION

Five patients received levofloxacin 500 mg/day and one patient received levofloxacin 125 mg/day All patients received continuous renal replacement therapy: CVVHDF on day 1 and CVVH on day 2, using an acrylonitrile hollow-fiber 0.9-m2 filter, constant blood flow rate of 90 ml/minute, substitution flow rate of 1 L/hour predilution, and dialysate flow rate of 1 L/hour (CVVHDF).

MEASUREMENTS AND MAIN RESULTS

Serum, ultrafiltrate, and dialysate concentrations of levofloxacin were determined by high-performance liquid chromatography. Extracorporeal clearance was 26.05 +/- 4.66 ml/hour during CVVHDF and 15.71 +/- 2.73 ml/hour during CVVH (p<0.05). Elimination half-life was 28.08 +/- 4.5 hours and 45.9 +/- 17.7 hours, and distribution volume was 1.51 +/- 0.52 L/kg and 1.42 +/- 0.42 L/kg for CVVHDF and CVVH, respectively. Saturation was 0.76 +/- 0.13 for CVVHDF versus a sieving coefficient of 0.77 +/- 0.16 for CVVH.

CONCLUSION

Marked extracorporeal elimination of levofloxacin occurs, requiring a dosage adjustment that can be calculated from the characteristics of CVVH and CVVHDF.

Susceptibility to fluoroquinolones among commonly isolated Gram-negative bacilli in 2000: TRUST and TSN data for the United States. Tracking Resistance in the United States Today. The Surveillance Network

From January to May 2000, as part of the Tracking Resistance in the United States Today (TRUST) surveillance initiative, clinical isolates of Enterobacteriaceae (n=2519) and non-fermentative Gram-negatives (n=580) were prospectively collected from 26 hospital laboratories across the United States. Isolates were tested for susceptibility to three fluoroquinolones (ciprofloxacin, levofloxacin, gatifloxacin) and seven other agents. In addition, data for the same period were collected from The Surveillance Network (TSN) Database-USA, an electronic surveillance network that receives data from more than 200 laboratories in the US. Both surveillance methods produced similar results. Against isolates of Enterobacteriaceae, imipenem was the most active agent, followed by the fluoroquinolones; > or = 86.7% of isolates of all species of Enterobacteriaceae except Providencia spp. were susceptible to fluoroquinolones by TRUST and TSN surveillance. TRUST identified differences in susceptibility to the three fluoroquinolones of > or = 2% for Citrobacter spp., Enterobacter cloacae, Proteus mirabilis and Serratia marcescens. Isolates of P. mirabilis were considerably more susceptible to levofloxacin (94.0%) than to ciprofloxacin (87.7%) and gatifloxacin (87.7%). Other results from TRUST included Pseudomonas aeruginosa being slightly more susceptible to ciprofloxacin (73.5%) and levofloxacin (73.0%) than gatifloxacin (71.0%). Imipenem was the only compound with significant activity (95.1% susceptible, TRUST; 87.4% susceptible, TSN) against Acinetobacter baumannii, but it was inactive against Stenotrophomonas maltophilia. S. maltophilia isolates were more susceptible to levofloxacin and gatifloxacin (77.7-79.8%) than ciprofloxacin (29.7-33.0%). Against 513 urinary isolates of Escherichia coli in TRUST, levofloxacin, gatifloxacin and ciprofloxacin were equipotent. Age and gender had no clear effect on the activity of levofloxacin, ciprofloxacin or gatifloxacin. Similar results for all three fluoroquinolones were seen in outpatients and inpatients. TRUST and TSN data indicated that resistance rates had not changed appreciably for any compound studied since a similar study conducted in 1999. TRUST centralized in vitro and electronic (TSN) surveillance methods provided an effective strategy for monitoring trends in resistance.

Levofloxacin

Levofloxacin is the L-form of the fluoroquinolone antibacterial agent, ofloxacin. In in vitro studies, levofloxacin demonstrated a broad range of activity against Gram-positive and -negative organisms and anaerobes. The drug is more active against Gram-positive organisms than ciprofloxacin, but less active than newer fluoroquinolones such as gatifloxacin. Its activity against Streptococcus pneumoniae is unaffected by the presence of penicillin resistance. In several randomised controlled trails, 5 to 14 days' treatment with intravenous and/or oral levofloxacin proved an effective therapy for upper and lower respiratory tract infections. In patients with mild to severe community-acquired pneumonia (CAP), intravenous and/or oral levofloxacin 500mg once or twice daily was as effective as intravenous and/or oral gatifloxacin, clarithromycin, azithromycin or amoxicillin/clavulanic acid. Overall, clinical response rates with levofloxacin ranged from 86 to 95% versus 88 to 96% with comparator agents; bacteriological response rates were 88 to 95% and 86 to 98%, respectively. Sequential (intravenous +/- oral switch) therapy with levofloxacin 750mg once daily was as effective as intravenous imipenem/cilastatin (+/- oral switch to ciprofloxacin) in patients with severe nosocomial pneumonia. Generally, oral levofloxacin 250 or 500mg once daily was at least as effective as oral cefaclor, cefuroxime axetil, clarithromycin or moxifloxacin in patients with acute exacerbations of chronic bronchitis as assessed by either clinical or bacteriological response rates. This approach also provided similar efficacy to amoxicillin/ clavulanic acid or clarithromycin in patients with acute sinusitis. Sequential therapy with levofloxacin 500mg twice daily for 7 to 14 days' was as effective as intravenous imipenem/cilastatin in patients with suspected bacteraemia. Oral levofloxacin 500mg once daily for 7 to 10 days was also an effective treatment in patients with uncomplicated skin and skin structure infections, and in those with complicated urinary tract infections. A higher dosage of sequential levofloxacin 750mg once daily proved as effective as intravenous ticarcillin/clavulanic acid (+/- oral switch to amoxicillin/clavulanic acid) in the treatment of complicated skin and skin structure infections. Pharmacoeconomic studies suggest that levofloxacin may be cost-saving in comparison to conventional therapies.

CONCLUSIONS

Levofloxacin continues to demonstrate good clinical efficacy in the treatment of a range of infections, including those in which S. pneumoniae is a potential pathogen. Importantly, it has efficacy in CAP similar to that of gatifloxacin and at least as good as that of the third generation cephalosporins. Extensive clinical data confirm the good tolerability profile of this agent without the phototoxicity, hepatic and cardiac events evident with some of the other newer fluoroquinolone agents. Levofloxacin therefore offers a unique combination of documented efficacy and tolerability, and provides an important option for the treatment of bacterial infections.

Community-acquired lower respiratory tract infections: etiology and treatment

The current therapy for community-acquired lower respiratory tract infections is often empiric, usually involving administration of a beta-lactam or macrolide. However, the increasing prevalence of antibiotic resistance in frequently isolated respiratory tract pathogens has complicated the antimicrobial selection process. This review will discuss the incidence of various respiratory pathogens, as well as update the clinician on the various antimicrobial alternatives available, with particular emphasis on the role of the newer fluoroquinolones in the treatment of acute exacerbations of chronic bronchitis and community-acquired pneumonia.

Efficacies of moxifloxacin, ciprofloxacin, and vancomycin against experimental endocarditis due to methicillin-resistant Staphylococcus aureus expressing various degrees of ciprofloxacin resistance

The new 8-methoxyquinolone moxifloxacin was tested against two ciprofloxacin-susceptible Staphylococcus aureus strains (strains P8 and COL) and two ciprofloxacin-resistant derivatives of strain P8 carrying a single grlA mutation (strain P8-4) and double grlA and gyrA mutations (strain P8-128). All strains were resistant to methicillin. The MICs of ciprofloxacin and moxifloxacin were 0.5 and 0.125 mg/liter, respectively, for P8; 0.25 and 0.125 mg/liter, respectively, for COL; 8 and 0.25 mg/liter, respectively, for P8-4; and >or=128 and 2 mg/liter, respectively, for P8-128. In vitro, the rate of spontaneous resistance of P8 and COL was 10(-7) on agar plates containing ciprofloxacin at two times the MIC, whereas it was <or=10(-10) on agar plates containing moxifloxacin at two times the MIC. Rats with experimental aortic endocarditis were treated with doses of drugs that simulate the kinetics in humans: moxifloxacin, 400 mg orally once a day; ciprofloxacin, 750 mg orally twice a day; or vancomycin, 1 g intravenously twice a day. Treatment was started either 12 or 24 h after infection and lasted for 3 days. Moxifloxacin treatment resulted in culture-negative vegetations in a total of 20 of 21 (95%) rats infected with P8, 10 of 11 (91%) rats infected with COL, and 19 of 24 (79%) rats infected with P8-4 (P < 0.05 compared to the results for the controls). In contrast, ciprofloxacin treatment sterilized zero of nine (0%) vegetations infected with first-level resistant mutant P8-4. Vancomycin sterilized only 8 of 15 (53%), 6 of 11 (54%), and 12 of 23 (52%) of the vegetations, respectively. No moxifloxacin-resistant derivative emerged among these organisms. However, moxifloxacin treatment of highly ciprofloxacin-resistant mutant P8-128 failed and selected for variants for which the MIC increased two times in 2 of 10 animals. Thus, while oral moxifloxacin might deserve consideration as treatment for staphylococcal infections in humans, caution related to its use against strains for which MICs are borderline is warranted.

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 adverse effects and drug interactions

Extensive pharmacologic and clinical development of quinolone antimicrobial agents has resulted in improved antimicrobial activity, pharmacokinetic features, toxicity, and drug-drug interaction profiles. Nalidixic acid and other early quinolones had limited use due to poor pharmacokinetics, relatively narrow antimicrobial spectrum of activity, and frequent adverse effects. Beginning with the development of fluoroquinolones, such as norfloxacin and ciprofloxacin, in the 1980s, the agents assumed a greatly expanded clinical role because of their broad antimicrobial spectrum of action, improved pharmacokinetic properties, and more acceptable safety profile. Although the pharmacokinetics and efficacy of the drugs have improved significantly, a major area of continued emphasis is to further reduce the frequency and severity of adverse events and drug-drug interactions. Older agents such as ciprofloxacin and ofloxacin are still extensively prescribed, but the focus of this article is on the newer fluoroquinolones (levofloxacin and other drugs that have been approved or have been under investigation since approximately 1997).