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

Is more than one quinolone needed in clinical practice?

OBJECTIVE

To review clinical information on fluoroquinolone antimicrobials to distinguish between these agents and help define their place in clinical practice.

DATA SOURCES

Primary and review articles on fluoroquinolones available commercially in the US as of August 2000 were identified through MEDLINE (from 1993-August 2000) and secondary sources.

STUDY SELECTION AND DATA EXTRACTION

All pertinent, published, clinical trials for levofloxacin, moxifloxacin, and gatifloxacin were included. Minimal data were included for quinolones with restricted or limited uses, including trovafloxacin, sparfloxacin, enoxacin, and lomefloxacin. Due to the quantity of data on ciprofloxacin, only more recent or pivotal trials or articles summarizing data on specific infections were included. Relevant information was included if it was believed to assist in differentiating between the fluoroquinolones for infections for which these agents would most commonly be considered.

DATA SYNTHESIS

Fluoroquinolones are a potent class of intravenous and oral broad-spectrum antimicrobial agents used for treating a wide range of community-acquired and nosocomial infections. More than 10 quinolones have been approved for use; although some of these have been withdrawn from the market, numerous others are under investigation. It has become increasingly important to be able to differentiate between these agents.

CONCLUSIONS

Differences in safety, antimicrobial spectrum of activity, and resistance development support the selective use of various fluoroquinolones in differing clinical situations.

The Role of Quinolones in Upper Respiratory Tract Infections

Fluoroquinolones are widely used in clinical practice because of their advanced pharmacokinetic properties, potential activity against most bacterial species, excellent clinical responses, and few side effects. Quinolones have no role in the treatment of pharyngitis or simple otitis media. Until recently, the available fluoroquinolones were not indicated for the treatment of acute purulent sinusitis because of their perceived inactivity against Streptococcus pneumoniae. Although not generally considered to be drugs of first choice, older quinolones have efficacy similar to that of cephalosporins and b-lactams in randomized clinical trials. Well-conducted clinical trials have shown that the new fluoroquinolones are as effective as standard comparators in patients with suspected or proven acute bacterial sinusitis and may allow shorter treatment. Ciprofloxacin remains the fluoroquinolone of choice for chronic otitis media and malignant otitis media. The new "respiratory" fluoroquinolones have microbiologic and pharmacokinetic advantages over the older agents. Clinical trials have confirmed clinical activity, but superiority compared with older agents has not been conclusively shown. Trials devised to demonstrate clinical or pharmacoeconomic benefits are still required.

Can antimicrobial susceptibility testing results for ciprofloxacin or levofloxacin predict susceptibility to a newer fluoroquinolone, gatifloxacin?: Report from The SENTRY Antimicrobial Surveillance Program (1997-99)

A serious problem confronting clinical laboratories and hospital formulary practices is the delayed availability of approved, commercially prepared susceptibility test reagents for newer antimicrobials. A current example is gatifloxacin, a new 8-methoxy fluoroquinolone with expanded potency against many Gram-positive pathogens. This study addresses the use of "surrogate marker" fluoroquinolones to predict susceptibility for gatifloxacin. Reference broth microdilution MIC results for 29,632 strains isolated in United States medical centers (SENTRY Antimicrobial Surveillance Program, 1997-99) were used: staphylococci (9,940 strains), enterococci (2,570), Streptococcus pneumoniae (3,784), Enterobacteriaceae (10,670) and Pseudomonas aeruginosa (2,668). Gatifloxacin interpretation categories were compared to those of ciprofloxacin and levofloxacin by regression statistics and error rate bounding analyses. For the Enterobacteriaceae, the absolute categorical agreement was 97.9 to 98.7% (false-susceptible or very-major error [VME], 0.03%-0.1%) for comparisons of both ciprofloxacin and levofloxacin with gatifloxacin. P. aeruginosa testing was more problematic (higher minor error rates), but acceptable at 0.6% to 1.1% VME and a 85.7% to 89.9% overall agreement. Ciprofloxacin results used to predict gatifloxacin in Gram-positive species was almost without VME (0.0%-0.2%) because gatifloxacin was significantly superior against these species, especially for S. pneumoniae, where gatifloxacin (MIC(90,) 0.5 microg/ml) was fourfold more potent than levofloxacin (MIC(90,) 2 microg/ml). The preferred gatifloxacin predictor drug was ciprofloxacin for all species except S. pneumoniae and P. aeruginosa, where levofloxacin results had a slightly greater predictive value. Susceptibility testing results for selected currently available fluoroquinolones can be used to predict susceptibility to gatifloxacin with high confidence. Many Gram-positive cocci, however, will be categorized as false-resistant by this interim method since gatifloxacin has a 11% to 34% wider spectrum of activity compared to ciprofloxacin when testing staphylococci and enterococci. Clinical laboratories can reliably use these suggested "surrogate markers" until reliable tests for gatifloxacin become available.

Quinolone Resistance: Older Concepts and Newer Developments

New quinolone compounds have been recommended for use in the treatment of respiratory tract infections, particularly pneumonia caused by multi drug-resistant Streptococcus pneumoniae. Of concern, however, is the recent emergence of pneumococcal isolates with reduced susceptibilities to both old and new quinolone compounds. This necessitates the employment of quinolone-use strategies aimed at restricting the emergence of resistance, to extend the effectiveness of this very important class of antibacterial agents. This article provides a comprehensive review of the recent discoveries in type II topoisomerase/quinolone structure-function relationships. It also addresses new insights into the mechanisms of quinolone resistance, the predicted trends in quinolone resistance, and possible strategies for quinolone use against S. pneumoniae.

Randomized, double-blind, multicenter trial comparing clinafloxacin with imipenem as empirical monotherapy for febrile granulocytopenic patients

In a double-blind, multicenter trial, 541 febrile granulocytopenic patients were randomized to receive either intravenous (iv) clinafloxacin (200 mg every 12 h) or i.v. imipenem (500 mg every 6 h) as empirical monotherapy. More baseline pathogens were susceptible to clinafloxacin (259 [99%] of 262 organisms) than to imipenem (253 [95%] of 265; P=.03). Initial favorable clinical response rates for clinafloxacin (88 [32%] of 272 patients) and imipenem (89 [33%] of 269) were similar. After addition of other antimicrobial agents, overall response rates were 259 (95%) of 272 for clinafloxacin and 251 (93%) of 269 for imipenem. During the study, only 13 clinafloxacin (5%) and 18 imipenem (7%) recipients died. Both drugs were generally well tolerated. Drug-related skin rash occurred more often with clinafloxacin (11% vs. 6%; P=.07), whereas nausea (2% vs. 5%; P=.16), Clostridium-difficile-associated diarrhea (3% vs. 8%; P=.02), and seizures (0% vs. 2%; P=.06) occurred more often with imipenem. These results suggest that clinafloxacin and imipenem have similar efficacy as empirical monotherapy in febrile granulocytopenic patients.

Antibiotic side effects

Antibiotic side effects are approached best from an individual agent perspective rather than from a class-related standpoint. As this article indicates, with the exception of drug fevers and drug rashes, most antibiotic side effects are related to individual agents and not class side effects. Clinicians should view antimicrobial side effects as related to each organ system and be aware that more often a nonmicrobial medication is the explanation for the drug side effect rather than the antimicrobial. Nonantimicrobial medications are the most common cause of drug fever; among antimicrobials, beta-lactams and sulfonamides are the most common causes of drug-induced fevers. Antimicrobial side effects have important implications for the patient, legal and economic implications for the hospital, and medicolegal implications for the physician. Antibiotic side effects that prolong hospitalization in today's managed care environment have important economic implications. Clinicians should be familiar with the most common side effects of the most frequently used antimicrobials, to minimize the potential of having adverse reactions occur in patients. Most adverse events related to antimicrobials are reversible rapidly on cessation of the medication. Irreversible toxicities include aminoglycoside-induced ototoxicity, Stevens-Johnson syndrome, and toxicity secondary to nitrofurantoin. The most common acute fatal drug reactions include hypersensitivity reactions resulting in anaphylaxis or the Stevens-Johnson syndrome and fatal hepatic necrosis secondary to trovafloxacin. Clinicians should eliminate the use of drugs associated with chronic or fatal toxicities because multiple therapeutic alternatives exist for virtually every potential infection.

Anaphylactoid reaction to levofloxacin

Anaphylactoid and/or anaphylactic reactions to fluoroquinolones are estimated to occur in 0.46-1.2/100,000 patients. A 49-year-old woman with a history of asthma was admitted for a presumed asthma exacerbation related to an infectious process. She was given levofloxacin and standard management for an acute exacerbation. On two occasions the patient's respiratory distress worsened, requiring intubation. The second reaction occurred immediately after levofloxacin administration and was accompanied by a marked cutaneous reaction. Levofloxacin was discontinued, and supportive care was provided. No further symptoms occurred. The patient later was found to have been started on levofloxacin before admission for a suspected upper respiratory infection.

Levofloxacin pharmacokinetics and serum bactericidal activities against five enterobacterial species

After oral administration of 500 mg of levofloxacin to 12 volunteers, we investigated the pharmacokinetics and serum bactericidal activities (SBAs) against five strains of members of the family Enterobacteriaceae. Pharmacokinetic data were as follows: maximum concentration in serum, 6.36 +/- 0.57 mg/liter; area under the concentration-time curve, 43.6 +/- 6.23 mg. h/liter; elimination half-life 4.23 +/- 0.87 h. SBAs were present for 24 h against Escherichia coli and Citrobacter freundii. The SBAs at 1, 12, and 24 h after administration against E. coli were 1:108, 1:29, and 1:7, respectively, and those against Citrobacter freundii were 1:74, 1:25, and 1:7, respectively. The SBAs were present for 12 h against the other three organisms tested. The SBAs against Serratia marcescens were 1:28 and 1:9 at 1 and 12 h, respectively; the SBAs against Klebsiella pneumoniae were 1:25 and 1:7 at 1 and 12 h, respectively; and the SBAs against Enterobacter cloacae were 1:24 and 1:10 at 1 and 12 h, respectively.

Proarrhythmic effects of fluoroquinolone antibacterial agents: in vivo effects as physiologic substrate for torsades

Drug-induced prolongation of the QT interval is often associated with the onset of Torsades de Pointes (TdP) resulting in a life-threatening ventricular arrhythmia. The potential of the proarrhythmic effects of the new fluoroquinolone antibacterial agents, levofloxacin and sparfloxacin, was examined in the chronic complete atrioventricular block dogs with stable idioventricular automaticity using Holter ECG monitoring in conscious state (Experiment 1). Next, to better analyze the mechanisms of the proarrhythmic property, the cardiovascular effects of these two drugs were compared in the halothane-anesthetized dogs under the monitoring of ECG, His bundle electrogram, systemic and left ventricular pressure, monophasic action potential, cardiac output, and effective refractory period (Experiment 2). In Experiment 1, oral administration of 6 mg/kg (n = 4) as well as 60 mg/kg (n = 4) of levofloxacin did not induce any ventricular premature depolarization. On the other hand, oral administration of 60 mg/kg of sparfloxacin (n = 4) induced TdP leading to ventricular fibrillation in all animals within 24 h, while 6 mg/kg of sparfloxacin (n = 4) did not induce any ventricular premature depolarization. In Experiment 2, intravenous administration of 0.3 mg/kg as well as 3.0 mg/kg of levofloxacin slightly increased cardiac output, but no significant changes were detected in the other parameters (n = 6). On the other hand, intravenous administration of 0.3 mg/kg of sparfloxacin prolonged the effective refractory period. Additional administration of 3.0 mg/kg of sparfloxacin decreased the heart rate and prolonged the effective refractory period and ventricular repolarization phase in a similar extent, but no significant changes were detected in the other parameters (n = 6). These results suggest that backward shift of the relative repolarization period in a cardiac cycle may be the mechanism responsible for the torsadegenic effect of sparfloxacin.

[Oral levofloxacin versus intravenous ceftriaxone and amoxicillin/clavulanic acid in the treatment of community-acquired pneumonia that requires hospitalization]

BACKGROUND

Levofloxacin, an antibiotic from the quinolone family, which is used with success in the ambulatory treatment of patients with community-acquired pneumonia, has been recently introduced to the pharmaceutical market. The purpose of this study was to compare the effectiveness and tolerance of oral (v.o.) levofloxacin (LVF) versus intravenous (i.v.) amoxicillin/clavulanate (AMX/CL) and ceftriaxone (CTX) in the treatment of the community-acquired pneumonia that require hospitalization (CAPH).

PATIENTS AND METHOD

In this prospective and randomized study 84 patients were included, 28 per group, from both sex with CAPH. The patients were assigned randomly to receive one of the next treatments: AMX/CL, 1.02 g i.v. every 8 h, CTX, 1 g i.v. every 12 h or LVF, 500 mg v.o. every 24 h. At the beginning clinical, biochemical and radiological characteristics were recorded from each case and at the 72 h the effect of treatment was evaluated using the evolution of the thermal curve and radiological images. The quantitative variables were analyzed with ANOVA, the qualitatives parameters with *2 test and Yates correction. The level of signification was * = 0.05.

RESULTS

Age, sex, clinical presentation, biochemical measurements and radiological images in the 3 groups were similar and no adverse effects were recorded in any of them. Number of patients with favorable outcome in the groups AMX/CL, CTX and LVF was 25 (89%), 25 (89%) and 26 (93%); p = 0,870.

CONCLUSIONS

Levofloxacin can be a simple, effective and safe therapeutic option for patients with CAPH.

Pharmacokinetics of ofloxacin enantiomers after intravenous administration for antibiotic prophylaxis in biliary surgery

The pharmacokinetics of S-(-)- and R-(+)-ofloxacin, enantiomers of the fluoroquinolone ofloxacin, were characterized after prophylactic administration in 15 patients undergoing elective biliary surgery. A single dose of ofloxacin 400 mg given intravenously as an infusion was administered 1 hour before surgery. Plasma levels of S-(-)- and R-(+)-ofloxacin showed very small differences between both enantiomers, although the ratio of S-(-)- to R-(+)-enantiomer concentration in plasma showed significant differences (p < 0.05) at 4 and 12 hours. Adequate S-(-)-ofloxacin (levofloxacin, the active enantiomer) plasma levels (> or = minimum inhibitory concentration [MIC90] for Escherichia coli) were found throughout the procedure. For pharmacokinetic parameters, the authors found small but statistically significant differences (p < 0.05) in the area under the concentration-time curve, AUC0-infinity (22.30 +/- 2.72 mg h/L for S-(-)-ofloxacin vs. 20.50 +/- 2.06 mg h/L for R-(+)-ofloxacin), and in the clearance (0.15 +/- 0.04 L/h/Kg for S-(-)-ofloxacin vs. 0.16 +/- 0.04 L/h/Kg for R-(+)-ofloxacin). To test the penetration of ofloxacin enantiomers into tissues, the authors measured levels in subcutaneous cell tissue and gall-bladder cell tissue. They did not observe statistical differences between the two isomers, which means that distribution is not an estereoselective process. Enantiomer levels in these two tissues decreased rapidly, but the highest concentrations were reached during the 4 first hours (i.e., when the surgical procedure was being performed). In conclusion, with the prophylactic treatment used, levofloxacin plasma and tissue levels are high enough to prevent surgical infections.

The safety profile of the fluoroquinolones

BACKGROUND

Premarketing trials showed the fluoroquinolone agents to have a favorable side-effect profile, with treatment-related adverse events comprising gastrointestinal, central nervous system, and dermatologic effects that were generally mild and reversible on cessation of treatment. However, postmarketing surveillance studies have identified severe adverse events, including severe anaphylaxis, QTc-interval prolongation, and potential cardiotoxicity, associated with 3 quinolone agents that either resulted in the removal of the agent from the market (temafloxacin and grepafloxacin) or significantly restricted its use due to substantial mortality and morbidity associated with liver toxicity (trovafloxacin). To date, there have been no such significant adverse events associated with the older fluoroquinolone agents, including ciprofloxacin, ofloxacin, norfloxacin, and levofloxacin. However, there are fewer data from postmarketing surveillance studies on the most recently approved agents, such as moxifloxacin and gatifloxacin, or agents awaiting approval, such as gemifloxacin.

OBJECTIVE

This paper examines safety data from the premarketing trials and postmarketing surveillance studies of fluoroquinolones available in the United States.

METHODS

A MEDLINE search was performed to identify all English-language studies published since 1980 concerning the safety profiles of the fluoroquinolones.

CONCLUSIONS

The fluoroquinolone antibacterial agents offer broad-spectrum therapy in patients with a variety of infections. Given similar spectra of activity, the choice between quinolones may be based on differences in efficacy and safety or tolerability profiles. Most drug reactions involving these agents are minor and reversible on discontinuing treatment, but adverse effects can be associated with significant mortality and morbidity, as was seen in the case of trovafloxacin and temafloxacin.

Fluoroquinolones

The fluoroquinolone class of antimicrobial agents has expanded dramatically in the last 5 years and will continue to grow over the next decade. This article discusses the newer fluoroquinolones in detail, including pharmacokinetics, pharmacodynamics, safety, and drug interactions, and the spectrum of in vitro activity. Newer agents are compared and contrasted with the older ones, particularly ciprofloxacin and ofloxacin, and problems with liver toxicity and trovafloxacin are described. Finally, appropriate use of the fluoroquinolones is discussed, including their role in the treatment of urinary tract infections, sexually transmitted diseases, gastrointestinal infections, osteomyelitis, and respiratory tract infections.

Pharmacokinetics and pharmacodynamics of levofloxacin against Streptococcus pneumoniae and Staphylococcus aureus in human skin blister fluid

The pharmacokinetics of levofloxacin in serum and in skin blister fluid (SBF) was determined for 20 volunteers after a single 500-mg oral dose of levofloxacin. In addition, ex vivo bactericidal activity of SBF against Streptococcus pneumoniae and Staphylococcus aureus was studied. SBF containing levofloxacin and granulocytes killed 5.2 log of Streptococcus pneumoniae bacteria and 2.0 log of Staphylococcus aureus bacteria during a 6-h incubation.

Outcomes of patients with multidrug-resistant pulmonary tuberculosis treated with ofloxacin/levofloxacin-containing regimens

OBJECTIVE

To analyze outcomes of patients with multidrug-resistant tuberculosis (MDR-TB) treated with ofloxacin/levofloxacin-containing regimens.

MATERIALS AND METHODS

From February 1990 through June 1997, 63 MDR-TB patients (with bacillary resistance to at least isoniazid and rifampin in vitro) were analyzed retrospectively. Twenty-two patients (34.9%) had had no previous antituberculosis chemotherapy. Each patient received either ofloxacin (53) or levofloxacin (10) even though 13 patients had bacilli resistant to ofloxacin in vitro. The other accompanying drugs mainly included aminoglycosides, cycloserine, ethionamide/prothionamide, and pyrazinamide. Sputum smear and culture examinations for acid-fast bacilli (AFB) were performed monthly for the initial 6 months and then at 2- to 3-month intervals until the end of treatment. Comparison was made between clinical successes and failures using univariate and multiple logistic regression analyses for the following variables: age, sex, presence of cavitation, extent of disease, sputum smear positivity, in vitro resistance to ofloxacin, in vitro resistance to streptomycin and/or ethambutol, treatment adherence, and the number of drugs per regimen.

RESULTS

Fifty-one patients (81.0%) were cured, nine patients (14.3%) failed, and three patients (4.7%) died. For the entire group, the mean duration of treatment was 14.0 months, and the mean number of drugs was 4.7. Mean durations of chemotherapy in successful and failed patients were 14.5 and 14.2 months, respectively. Mean time for sputum smear and culture conversions were 1.7 and 2.1 months, respectively. Only cavitation, resistance to ofloxacin, and poor adherence were found to be variables independently associated with adverse outcomes (p < 0.05; odds ratios = 15.9, 13.5, 12.8, respectively). Negative sputum cultures after 2 and 3 months of therapy were 100% predictive of cure. Positive sputum cultures after 2 and 3 months were 52.3% and 84.6% predictive of failure, respectively. One patient (2.1%) relapsed after apparent cure. Twenty-five patients experienced adverse drug reactions, but only 12 of them needed drug modifications.

CONCLUSION

Most MDR-TB patients can be treated effectively with ofloxacin/levofloxacin-containing regimens. Presence of cavitation, resistance to ofloxacin in vitro, and poor adherence to therapy portend treatment failure. Monitoring monthly sputum culture for AFB in the initial months of chemotherapy helps predict clinical outcomes.

Antimicrobial activity evaluations of gatifloxacin, a new fluoroquinolone: contemporary pathogen results from a global antimicrobial resistance surveillance program (SENTRY, 1997)

OBJECTIVE: To investigate the in vitro potency and spectrum of activity of gatifloxacin and five comparator fluoroquinolones tested against over 23 000 clinical isolates from diverse geographic and clinical sources in the Americas. METHODS: Gram-negative, Gram-positive and fastidious bacterial isolates were tested against gatifloxacin, ciprofloxacin, levofloxacin, ofloxacin, sparfloxacin and trovafloxacin using broth microdilution methods recommended by the National Committee for Clinical Laboratory Standards (NCCLS). RESULTS: Gatifloxacin demonstrated a potency and spectrum very similar to those of other new fluoroquinolones such as levofloxacin, sparfloxacin, and trovafloxacin. Gatifloxacin was particularly active against the Enterobacteriaceae (94.8% susceptible at </=2 mg/L), Acinetobacter spp. (77.2%), Stenotrophomonas maltophilia (75.1%), Streptococcus pneumoniae (99.8%), other Streptococcus spp. (>/=98.9%), and various Staphylococcus spp. (79.2-100.0%). Trovafloxacin was the most similar comparison drug overall. CONCLUSIONS: These results indicate a potential therapeutic role for gatifloxacin that would widen the potency or spectrum of fluoroquinolones, particularly against Gram-positive species, when considering its favorable bioavailability.

Potential interactions of the extended-spectrum fluoroquinolones with the CNS

The new generation fluoroquinolones -- sparfloxacin, levofloxacin, grepafloxacin and trovafloxacin -- have been designed to respond to the clinical need for extended antimicrobial cover in the face of increasing global microbial resistance. Their main focus is in the treatment of respiratory infections, particularly those acquired in the community. CNS adverse effects, such as dizziness and headache, are known to occur relatively commonly with some fluoroquinolones and are not, in general, well tolerated by patients. The structural component of the fluoroquinolone molecule believed to be responsible for improved gram-positive activity is also believed to be implicated in the production of CNS adverse effects, including those arising from drug interactions with theophylline and NSAIDs. Inhibition of brain gamma-aminobutyric acid (GABA) receptor binding appears to be a strong indicator of CNS activity, though N-methyl-D-aspartate receptor binding has also been implicated. In accordance with the results of these predictive studies, clinical trials have found sparfloxacin, levofloxacin and grepafloxacin to be associated with a low incidence of CNS events. Trovafloxacin has been found to be associated with a higher incidence of CNS events (particularly lightheadedness and dizziness) than the other 3 agents. Ongoing and future clinical studies will help to define the usefulness of the predictive models, as well as reveal the full CNS adverse event profile of these and other investigational fluoroquinolones.

Comparative efficacies of levofloxacin and ciprofloxacin against Streptococcus pneumoniae in a mouse model of experimental septicaemia

The in vivo efficacies of levofloxacin and ciprofloxacin were compared against three clinical isolates of Streptococcus pneumoniae, using a mouse protection model. Two strains (SP 22 and SP 28) were penicillin-sensitive while one strain (SP 46) was penicillin-resistant. Each strain had identical susceptibility to both drugs. Using mice with renal impairment induced by uranyl nitrate injection, the elimination half-life of each antibiotic was prolonged to approximate human pharmacokinetic profiles of the drugs. The dosing regimen of each drug that yielded serum levels in mice which mimic human therapeutic concentrations of the drugs, were designed. One hour after intraperitoneal inoculation with minimum lethal dose of each strain, either levofloxacin at a dosing regimen of 10.6 mg/kg every 8 h or ciprofloxacin at 9.5 mg/kg every 8 h was subcutaneously administered for a total of six or 15 doses. In treatment, monitored daily for 5-8 days, levofloxacin resulted in higher survival compared with ciprofloxacin for the three strains. For example, percent survival following levofloxacin treatment recorded at day 4 postinfection with SP 22, SP 28 and SP 46 were 41, 90 and 30%, respectively, while the corresponding values after ciprofloxacin treatment were 27, 75 and 16%, respectively. However, statistical analysis did not reveal a significant difference (p > 0.05). The lack of significant difference observed in the efficacies of both drugs reflected the comparability of their 24-h AUC/MIC ratios. It is suggested that, with some strains of S. pneumoniae, the efficacy of levofloxacin may be equivalent to that of ciprofloxacin in the treatment of systemic pneumococcal infections caused by susceptible strains of the organism.

A randomized, crossover design study of the pharmacology of extended-spectrum fluoroquinolones for pneumococcal infections

STUDY OBJECTIVES

The objectives of this study were to characterize the single-dose and steady-state plasma pharmacokinetics of IV levofloxacin and IV alatrofloxacin, and to compare the results to pneumococcal isolate sensitivities in order to estimate the clinical efficacy of current community-acquired pneumonia treatment regimens against pneumococcal infections.

DESIGN

Two-way, open-label, randomized, crossover study.

PARTICIPANTS

Each of 12 healthy volunteer subjects received IV levofloxacin, 500 mg qd for 7 days, and IV alatrofloxacin, 200 mg qd for 7 days. The two regimens were separated by a 2-week washout period.

MEASUREMENTS AND RESULTS

Plasma concentration profiles were collected around the first and final doses of both regimens and were assayed for their respective quinolone concentrations. When the peak concentrations for both agents were compared to standard twofold dilution minimum inhibitory concentration (MIC) values for pneumococcal isolates, it was discovered that the breakpoint MIC value at which each compound would no longer achieve a peak plasma concentration/MIC ratio of at least 12:1 was 0.5 mg/L for levofloxacin and 0.25 mg/L for alatrofloxacin.

CONCLUSIONS

Based on the MIC that inhibits 90% of isolates of Streptococcus pneumoniae for both of these agents (1.0 to 2.0 mg/L for levofloxacin and 0.125 to 0.25 mg/L for trovafloxacin), our results indicate that although the once-daily regimen of alatrofloxacin appears to be appropriate for this pathogen, a more aggressive regimen may need to be investigated to optimize the clinical and microbiological effects of levofloxacin.

Eosinophilia Possibly Associated with Intravenous Levofloxacin

Objective:

To report the first published case of eosinophilia following the administration of intravenous levofloxacin.

Case Summary:

An 84-year-old white man was admitted for community-acquired pneumonia, for which he received intravenous levofloxacin therapy. The absolute eosinophil count on admission was 120 cells/mm3 (differential 3.5%). On day 6 of admission and therapy, the absolute eosinophil count peaked at 957 cells/mm3 (differential 16.8%) and then returned to a normal value of 1.2% on day 7, one day after discontinuation of levofloxacin.

Discussion:

Fluoroquinolones are broad-spectrum antimicrobials used frequently to treat a variety of infections. A review of MEDLINE (1996-May 1999) did not yield any previous reports of eosinophilia associated with intravenous levofloxacin therapy. However, many quinolones have been associated with eosinophilia, occasionally with significant associated morbidity. This patient's eosinophilia developed within one day of initiating levofloxacin and resolved within one day of discontinuation of the drug. To our knowledge, this is the first reported case of eosinophilia related to intravenous levofloxacin therapy.

Conclusions:

The temporal relationship of events in this case suggests that levofloxacin was the cause of this patient's eosinophilia. We report this case to alert clinicians to the possibility of eosinophilia associated with levofloxacin.

The new fluoroquinolones: A critical review

OBJECTIVE

This paper reviews the literature available on the new fluoroquinolones - clinafloxacin, gatifloxacin, grepafloxacin, levofloxacin, moxifloxacin, sparfloxacin and trovafloxacin - to compare these agents with each other and contrast them with ciprofloxacin, an older fluoroquinolone.

DATA SELECTION

Published papers used were obtained by searching MEDLINE for articles published between 1994 and 1998, inclusive. References of published papers were also obtained and reviewed. Abstracts from scientific proceedings were reviewed.

DATA EXTRACTION

Due to the limited data available on several of the agents, criteria for study inclusion in the in vitro, pharmacokinetics and in vivo sections were not restrictive.

DATA SYNTHESIS

The new fluoroquinolones offer excellent Gram-negative bacillary activity and improved Gram-positive activity (eg, against Streptococcus pneumoniae and Staphylococcus aureus) over ciprofloxacin. Clinafloxacin, gatifloxacin, moxifloxacin, sparfloxacin and trovafloxacin display improved activity against anaerobes (eg, Bacteriodes fragilis). All of the new fluoroquinolones have a longer serum half-life than ciprofloxacin (allowing for once daily dosing), and several are eliminated predominantly by nonrenal means. No clinical trials are available comparing the new fluoroquinolones with each other. Clinical trials comparing the new fluoroquinolones with standard therapy have demonstrated good efficacy in a variety of infections. Their adverse effect profile is similar to that of ciprofloxacin. Clinafloxacin and sparfloxacin cause a high incidence of phototoxicity (1.5% to 14% and 2% to 11.7%, respectively), grepafloxacin causes a high incidence of taste perversion (9% to 17%) and trovafloxacin causes a high incidence of dizziness (11%). They all interact with metal ion-containing drugs (eg, antacids), and clinafloxacin and grepafloxacin interact with theophylline. The new fluoroquinolones are expensive; however, their use may result in savings in situations where, because of their potent and broad spectrum of activity, they can be used orally in place of intravenous antibiotics.

CONCLUSIONS

The new fluoroquinolones offer advantages over ciprofloxacin in terms of improved in vitro activity and pharmacokinetics. Whether these advantages translate into improved clinical outcomes is presently unknown. The new fluoroquinolones have the potential to emerge as important therapeutic agents in the treatment of respiratory tract and genitourinary tract infections.

Comparison of the effectiveness of levofloxacin and amoxicillin-clavulanate for the treatment of acute sinusitis in adults

In this comparative trial, outpatients with acute sinusitis were randomly assigned to receive levofloxacin (500 mg orally once daily) or amoxicillin-clavulanate (500/125 mg orally 3 times daily) for 10 to 14 days. The success rates (cured and improved) 2 to 5 days after the end of treatment were 88.4% for the 267 clinically evaluable patients who received levofloxacin and 87.3% for the 268 clinically evaluable patients who received amoxicillin-clavulanate. Drug-related adverse events occurred in a smaller percentage of patients in the levofloxacin treatment group (7.4%) than in the amoxicillin-clavulanate treatment group (21.2%). The most common of these were nausea, diarrhea, vaginitis, and abdominal pain for levofloxacin-treated patients and diarrhea, vaginitis, nausea, genital moniliasis, abdominal pain, vomiting, and flatulence for amoxicillin-clavulanate-treated patients. The results of this study show that once-daily administration of levofloxacin is as effective and better tolerated than amoxicillin-clavulanate administered 3 times daily for treating acute sinusitis in adult outpatients.

Italian survey on comparative levofloxacin susceptibility in 334 clinical isolates of Pseudomonas aeruginosa

A national survey on susceptibility patterns of 334 Pseudomonas aeruginosa isolates from intensive care units and hematology and oncology wards from 13 Italian hospitals compared the in vitro activity of levofloxacin, an injectable oral fluoroquinolone, to those of ciprofloxacin, ofloxacin, ceftazidime, imipenem, amikacin, and gentamicin. Amikacin and imipenem had the best susceptibility profiles. The activity of levofloxacin was superior to those of the other quinolones and was comparable to that of ceftazidime. The effect of levofloxacin in vitro on P. aeruginosa clinical isolates suggests that further clinical investigations are warranted.

The bactericidal activity of levofloxacin against ampicillin-resistant and ampicillin-susceptible Haemophilus influenzae in comparison with ofloxacin, ciprofloxacin and sparfloxacin

The bactericidal activity of levofloxacin against four Haemophilus influenzae clinical isolates (two ampicillin-resistant and two susceptible) was compared with that of ofloxacin, ciprofloxacin and sparfloxacin at concentrations simulating the peak serum concentrations obtained with the recommended oral doses. Bactericidal activity was assessed using time-kill curves and minimum kill-time values. Both concentrations of levofloxacin rapidly killed all the study strains, with mean kill times of 4 h and no viable bacteria remaining after 18-h exposure. The bactericidal activities of levofloxacin, ofloxacin and sparfloxacin were similar. The minimum kill-times for both concentrations of ciprofloxacin were 28-35% longer than those of levofloxacin. These results support the use of levofloxacin for H. influenzae infections, including ampicillin-resistant strains.

Mechanism underlying levofloxacin uptake by human polymorphonuclear neutrophils

The mechanism of radiolabeled levofloxacin ([3H]levofloxacin) uptake by human polymorphonuclear neutrophils (PMNs) was investigated by a classical velocity centrifugation technique. PMNs were incubated with levofloxacin for 5 to 180 min under various conditions before centrifugation through an oil cushion. Radioactivity was measured in the cell pellet to determine the amount of cell-associated drug. The uptake of levofloxacin was moderate with a cellular concentration/extracellular concentration ratio of about 4 to 6. Levofloxacin accumulated in PMNs parallel to the extracellular concentration, without saturation, over the range of 2.5 to 200 mg/liter (linear regression analysis: r = 0.92; P < 0.001). The activation energy was low (36 +/- 7.2 kJ/mol). Levofloxacin uptake was increased in Ca(2+)-depleted, EGTA-containing medium by approximately 33% (P = 0.022), while Ni2+, a Ca2+ channel inhibitor, inhibited it in a concentration-dependent manner, with the concentration that inhibited 50% of control uptake being approximately 2.65 mM. Verapamil (an L-type Ca2+ channel inhibitor) and other pharmacologic agents which modify Ca2+ homeostasis did not modify levofloxacin uptake. Interestingly, Ca2+ and Mg2+ inhibited levofloxacin uptake in a concentration-dependent manner. EGTA, Ni2+, and verapamil did not modify levofloxacin efflux; thapsigargin, a Ca2+ pool-releasing agent, modestly increased the intracellular retention of levofloxacin. In addition, contrary to other fluoroquinolones, probenecid at 1 to 10 mM did not modify either levofloxacin uptake or efflux. These data are consistent with a mechanism of passive accumulation of levofloxacin in PMNs. Extracellular Ca2+ and Mg2+ may influence the structural conformation of levofloxacin or the lipophilicity of PMN membranes, thus explaining their effect on levofloxacin uptake.

Expanded activity and utility of the new fluoroquinolones: a review

In general, the fluoroquinolones developed over the past few years have greater potency, a broader spectrum of antimicrobial activity, greater in vitro efficacy against resistant organisms, and a better safety profile than other antimicrobial agents, including the older quinolones. The present review focuses on 4 new quinolones that are commercially available (levofloxacin, trovafloxacin, grepafloxacin, and sparfloxacin) and 3 that are currently undergoing clinical trials (gatifloxacin, moxifloxacin, and clinafloxacin). Examination of the minimum inhibitory concentrations of these drugs against gram-positive, gram-negative, anaerobic, and atypical organisms demonstrates their increased potency in vitro. The available clinical evidence, although sparse, suggests the potential enhanced efficacy of these drugs in the treatment of various community-acquired and nosocomial infections (eg, respiratory, urinary tract, and skin infections and sexually transmitted diseases). Compared with ciprofloxacin, their pharmacokinetic profiles demonstrate equivalent or greater bioavailability, higher plasma concentrations, and increased tissue penetration, as reflected in greater volume of distribution. Adverse events seen with most quinolones are mild. Serious adverse effects that may occur are phototoxicity (particularly with sparfloxacin) and prolongation of the QTc interval (seen with sparfloxacin and grepafloxacin). Drug interactions are possible between multivalent cation-containing compounds and all quinolones and between theophylline and both ciprofloxacin and grepafloxacin. Drugs that prolong the QTc interval should not be coadministered with sparfloxacin and grepafloxacin. Step-down therapy, a therapeutic and cost-saving advantage possible with gatifloxacin, levofloxacin, and moxifloxacin, allows the switching of patients from intravenous to oral therapy without having to change the dosage regimen or class of antibiotics. In addition to shortening the hospital stay and reducing the risk of venous complications, step-down therapy has been shown to cut hospital drug costs by 40% and hospitalization costs by 20%.

Efficacy and safety of oral levofloxacin compared with clarithromycin in the treatment of acute sinusitis in adults: a multicentre, double-blind, randomized study. The Canadian Sinusitis Study Group

Adult patients with acute sinusitis (n = 236) were randomized in a double-blind study to levofloxacin 500 mg orally once daily (n = 119) or clarithromycin 500 mg orally twice daily (n = 117) for 10-14 days. Between 2 and 5 days after therapy participants were evaluated as cured (no symptoms), improved (symptoms improved, no further therapy required), or failed (further therapy required). Clinical response rates (cured plus improved) for clinically evaluable patients were 93.9% for levofloxacin (n = 98) and 93.5% for clarithromycin (n = 93). The proportion of patients evaluated as cured was higher in the levofloxacin (40.8%) than in the clarithromycin arm (29.0%) and individual symptoms showed higher rates of resolution. Of patients receiving levofloxacin and clarithromycin, 22.5% and 39.3%, respectively, experienced adverse events related or possibly related to the study therapy. This study showed that, in the treatment of acute sinusitis, daily levofloxacin therapy is as effective as twice-daily clarithromycin therapy with more complete clearing of symptoms and a more tolerable side-effect profile.

Determination of protein binding of gyrase inhibitors by means of continuous ultrafiltration

In order to characterize the protein binding of a drug, it is necessary to have a method which is close to in vivo conditions and fast in the course of measurement. The continuous ultrafiltration fulfils both requirements for substances with a high extent of protein binding. In this study, 18 gyrase inhibitors in clinical practice, characterized by a lower extent of protein binding, were subjected to the titration procedure of the continuous ultrafiltration using bovine and human serum albumin (BSA, HSA), and human plasma. The results of the continuous ultrafiltration were found to be similar to those obtained by means of the 'classical' discontinuous ultrafiltration using plasma (correlation between continuous and discontinuous ultrafiltration r2 = 0.87). In the cases of pipemidic acid, enoxacin and rufloxacin, the continuous method gave approximately 20% lower degrees of protein binding than the discontinuous procedure, which utilizes plasma having the full range of proteins. It is likely that these drugs bind mainly to other proteins in plasma than HSA. This finding proves that this fast method is worthwhile in the whole range of protein binding.

Levofloxacin: a therapeutic review

This therapeutic review discusses the pharmacology, pharmacokinetics, in vitro activity, drug interactions, and adverse effects of levofloxacin, a fluoroquinolone antibiotic. Particular emphasis is placed on the clinical efficacy of levofloxacin and its place in therapy. Compared with ciprofloxacin and the earlier quinolone agents, levofloxacin has an improved pharmacokinetic profile that allows convenient once-daily dosing in either an oral or parenteral formulation. Levofloxacin has enhanced activity against gram-positive aerobic organisms, including penicillin-resistant pneumococci. In published comparative trials involving commonly used treatment regimens, levofloxacin had equivalent if not greater activity in the treatment of community-acquired pneumonia, acute bacterial exacerbations of chronic bronchitis, acute bacterial sinusitis, acute pyelonephritis, and complicated urinary tract infection. Levofloxacin is well tolerated and induces minimal adverse drug reactions. Based on the above attributes, it may be reasonable to include levofloxacin on the hospital formulary in place of older quinolones. More recently released quinolones such as trovafloxacin exhibit similar advantages; however, until direct comparative trials between levofloxacin and these newer agents are conducted, it is difficult to advocate one agent over another. Regardless of which quinolone is the primary agent on the formulary, it is imperative that this class of antimicrobial drugs be used with discretion to minimize the development of resistance.

In vitro susceptibility of recent gram-positive isolates to ciprofloxacin, levofloxacin, and trovafloxacin

Gram-positive isolates (n = 290) were tested for their susceptibility to three fluoroquinolone antibiotics by standard disk-diffusion technology. Overall, 59%, 72%, and 85% were susceptible and 29%, 25%, and 11% were resistant to ciprofloxacin, levofloxacin, and trovafloxacin, respectively. Of Staphylococcus aureus isolates (n = 84), 55%, 57%, and 88% were susceptible to the three antibiotics, respectively. Staphylococcus epidermidis (n = 45), too, was more susceptible to trovafloxacin, although the differences were smaller (60%, 62%, and 78%). Of 35 Enterococcus faecalis isolates, 66% and 74% were susceptible to levofloxacin and trovafloxacin, respectively, but only 9% were susceptible to ciprofloxacin.

Clinical applications of quinolones

The quinolone antimicrobials are the class of inhibitors of bacterial topoisomerases that has been developed most fully for clinical use in human medicine. Initial members of the class had their greatest potency against Gram-negative bacteria, but newly developed members have exhibited increased potency against Gram-positive bacteria and soon agents will be available with additional activity against anaerobic bacteria, providing a broad spectrum of potency. After nalidixic acid, the earliest member of the class which was used for treatment of urinary tract infections, the later fluoroquinolone congeners have had sufficient potency, absorption, and distribution into tissue for additional uses in treatment of sexually transmitted diseases, infections of the gastrointestinal tract, respiratory tract, skin, and bones and joints. Tolerability of these agents in usual doses has been good. Acquired bacterial resistance resulting from clinical uses has occurred in particular among staphylococci and Pseudomonas aeruginosa. Intense drug use and ability of resistant pathogens to spread have also contributed to development of resistance in initially more susceptible pathogens such as Escherichia coli and Neisseria gonorrhoeae in certain settings. Preservation of the considerable clinical utility of the quinolone class for the long term will be affected by the extent to which their use is judicious.

Levofloxacin. Its use in infections of the respiratory tract, skin, soft tissues and urinary tract

Levofloxacin, the optically pure levorotatory isomer of ofloxacin, is a fluoroquinolone antibacterial agent. Like other fluoroquinolones, it acts on bacterial topoisomerase and has activity against a broad range of Gram-positive and Gram-negative organisms. Levofloxacin also appears to have improved activity against Streptococcus pneumoniae compared with ciprofloxacin or ofloxacin. Levofloxacin distributes well and achieves high levels in excess of plasma concentrations in many tissues (e.g., lung, skin, prostate). High oral bioavailability allows switching from intravenous to oral therapy without dosage adjustment. In patients with mild to severe community-acquired pneumonia receiving treatment for 7 to 14 days, oral levofloxacin was similar in efficacy to amoxicillin/clavulanic acid, and intravenous and/or oral levofloxacin was superior to intravenous ceftriaxone and/or oral cefuroxime axetil. With levofloxacin use, clinical success (clinical cure or improvement) rates were 87 to 96% and bacteriological eradication rates were 87 to 100%. In the 5- to 10-day treatment of acute exacerbations of chronic bronchitis, oral levofloxacin was similar in efficacy to oral cefuroxime axetil or cefaclor. Levofloxacin resulted in clinical success in 78 to 94.6% of patients and bacteriological eradication in 77 to 97%. Oral levofloxacin was also similar in efficacy to amoxicillin/clavulanic acid or oral clarithromycin in patients with acute maxillary sinusitis treated for 7 to 14 days. Equivalence between 7- to 10-day therapy with oral levofloxacin and ciprofloxacin was seen in patients with uncomplicated skin and soft tissue infections. Clinical success was seen in 97.8 and 96.1% of levofloxacin recipients and bacteriological eradication in 97.5 and 93.2%. Complicated urinary tract infections, including pyelonephritis, responded similarly well to oral levofloxacin or ciprofloxacin for 10 days or lomefloxacin for 14 days. Clinical success and bacteriological eradication rates with levofloxacin occurred in 92 to 93.3% and 93.6 to 94.7% of patients.

CONCLUSIONS

Levofloxacin can be administered in a once-daily regimen as an alternative to other fluoroquinolones in the treatment of infections of the urinary tract, skin and soft tissues. Its more interesting use is as an alternative to established treatments of respiratory tract infections. S. pneumoniae appears to be more susceptible to levofloxacin than to ciprofloxacin or ofloxacin. Other newer fluoroquinolone agents that also have enhanced in vitro antipneumococcal activity may not share the well established tolerability profile of levofloxacin, which also appears to improve on that of some older fluoroquinolones.

A comparison of the activity of ciprofloxacin and levofloxacin with other agents against respiratory tract pathogens

In a study involving 15 UK hospitals, sequential respiratory tract isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis were studied. The susceptibility of these strains to two fluoroquinolones, ciprofloxacin and levofloxacin were compared to those of currently used macrolides and beta-lactams. The activity of ciprofloxacin and levofloxacin against S. pneumoniae was not statistically significantly different (geometric mean MIC 0.978 and 0.95 mg/L respectively). Beta-lactam resistance did not affect fluoroquinolone susceptibility. H. influenzae and M. catarrhalis were highly susceptible to both fluoroquinolones.

Levofloxacin versus ciprofloxacin versus lomefloxacin in acute pyelonephritis

OBJECTIVES

To evaluate, in two randomized, multicenter trials, levofloxacin compared with ciprofloxacin and lomefloxacin for efficacy and safety in treating acute pyelonephritis.

METHODS

We enrolled a total of 186 patients with bacteriologically proved infection. Of these, 89 patients in both trials combined received levofloxacin 250 mg once daily; 58 received ciprofloxacin 500 mg twice daily in the first trial (double blind); and 39 received lomefloxacin 400 mg once daily in the second trial (open label). Microbiologic response of patients evaluable for microbiologic efficacy was the primary efficacy variable, and clinical response of microbiologically evaluable patients was the secondary efficacy variable in both studies.

RESULTS

Escherichia coli was the most prevalent pathogen. At 5 to 9 days after the end of treatment, 95% of uropathogens were eradicated in patients who received levofloxacin compared with 94% in the ciprofloxacin-treated group and 95% in the lomefloxacin-treated group. The clinical cure rate was 92% for levofloxacin in both studies combined, 88% for ciprofloxacin, and 80% for lomefloxacin. Drug-related adverse events were reported by 2% of levofloxacin-treated patients, 8% of ciprofloxacin-treated patients, and 5% of lomefloxacin-treated patients.

CONCLUSIONS

The once-daily oral administration, proven efficacy, and good tolerability make levofloxacin an excellent choice for empiric treatment of acute pyelonephritis.

Sparfloxacin but not levofloxacin or ofloxacin prolongs cardiac repolarization in rabbit Purkinje fibers

Sparfloxacin, a fluoroquinolone antibacterial, has been reported to prolong cardiac repolarization in some patients. In this study, we have investigated the in vitro cardiac electrophysiological effects of two other fluoroquinolones, levofloxacin and ofloxacin, and compared them with those exerted by sparfloxacin. Cardiac action potentials have been recorded from rabbit Purkinje fibers using conventional glass microelectrodes. The influence of a sudden decrease in stimulation rate on repolarization is examined. It is found that ofloxacin and levofloxacin (1-100 microM) do not alter the action potential parameters even at a concentration as high as 100 microM. The stimulation rate is without effect on repolarization. On the contrary, sparfloxacin (1-100 microM) lengthens concentration-dependently the duration of action potential, this effect being significant from the concentration of 10 microM. A non significant decrease in maximal rate of rise of phase 0 depolarization was observed at the concentration of 100 microM. Under low stimulation rate, the sparfloxacin-induced prolonging effect was magnified and early afterdepolarizations occurred in one of seven fibers from the concentration of 30 microM and in four other fibers at the concentration of 100 microM. These results suggest that levofloxacin and ofloxacin had no effect on cardiac cellular electrophysiology whereas sparfloxacin exerts pure class III electrophysiological effects, which can explain the prolongation of QT interval observed clinically in some patients and might become arrhythmogenic in the presence of other predisposing factors.

In vitro activity of levofloxacin against a selected group of anaerobic bacteria isolated from skin and soft tissue infections

The in vitro activity of levofloxacin was compared to the activities of ofloxacin, ciprofloxacin, ampicillin-sulbactam (2:1), cefoxitin, and metronidazole for a selected group of anaerobes (n = 175) isolated from skin and soft tissue infections by using the National Committee for Clinical Laboratory Standards-approved Wadsworth method. Ampicillin-sulbactam and cefoxitin inhibited 99% of the strains of this select group, levofloxacin and ofloxacin inhibited 73 and 50%, respectively, at 2 microg/ml, and ciprofloxacin inhibited 51% at 1 microg/ml. The geometric mean MIC of levofloxacin was lower than those of ofloxacin and ciprofloxacin for every group except Veillonella.

A controlled trial of levofloxacin and lomefloxacin in the treatment of complicated urinary tract infection

OBJECTIVES

The efficacy and safety of levofloxacin and lomefloxacin in complicated urinary tract infections (UTIs) were compared in a randomized, open-label, multicenter study.

METHODS

Outpatients were randomized to receive levofloxacin (250 mg once daily) for 7 to 10 days or lomefloxacin (400 mg once daily) for 14 days. Three hundred thirty-six patients (171 with levofloxacin, 165 with lomefloxacin) were evaluable for microbiologic efficacy, and 461 patients (232 with levofloxacin, 229 with lomefloxacin) for safety.

RESULTS

The overall microbiologic eradication rate of pathogens was 95.5% (168 of 176) for levofloxacin and 91.7% (154 of 168) for lomefloxacin. Eradication rates with respect to patients were 95.3% (163 of 171) and 92.1% (152 of 165) for levofloxacin and lomefloxacin, respectively. At the 5 to 9-day post-therapy visit, symptoms were completely resolved in 84.8% of levofloxacin-treated patients and were decreased in 8.2% (93.0% clinical success). Among the lomefloxacin-treated patients, complete resolution was seen in 82.4%, with decreased symptoms in 6.1% (88.5% clinical success). Drug-related adverse events (AEs) were reported by 10 (2.6%) and 18 (5.2%) levofloxacin- and lomefloxacin-treated patients, respectively. Compared with levofloxacin-treated patients, more lomefloxacin-treated patients experienced photosensitivity reactions (3 [1.3%] versus 0) and dizziness (2 [0.9%] versus 0). Nausea (3 [1.3%] versus 1 [0.4%]) was more frequent in the levofloxacin-treated group. Six patients in each treatment group had a gastrointestinal AE (1.7%); rash was reported more frequently with lomefloxacin (4 patients [0.4%]) than with levofloxacin (1 patient [0.4%]). Discontinuation because of AEs was observed in 8 (3.4%) levofloxacin- and 14 (6.1%) lomefloxacin-treated patients.

CONCLUSIONS

Once-daily levofloxacin is as effective as and has a superior tolerability profile than lomefloxacin in the treatment of complicated UTIs.

Open-label assessment of levofloxacin for the treatment of acute bacterial sinusitis in adults

PURPOSE

To evaluate the efficacy and safety of levofloxacin (500 mg orally once daily for 10 to 14 days) in treating adult outpatients with acute bacterial sinusitis.

PATIENTS AND METHODS

A total of 329 patients enrolled in the study at 24 centers. All patients had a pre-therapy Gram's stain and culture of sinus exudate obtained by antral puncture or nasal endoscopy. Clinical response was assessed on the basis of signs and symptoms and sinus radiograph or computed tomography results. Microbiologic cure rates were determined on the basis of presumed plus documented eradication of the pre-therapy pathogen(s).

RESULTS

The most common pathogens were Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, and Moraxella catarrhalis. Of 300 clinically evaluable patients, 175 (58%) were cured and 90 (30%) were improved at the post-therapy evaluation, resulting in a clinical success rate of 88%. Thirty-five patients (12%) clinically failed treatment. The microbiologic eradication rate (presumed plus documented) among 138 microbiologically evaluable patients was 92%. Microbiologic eradication rates (presumed plus documented) of the most common pathogens ranged from 93% (M. catarrhalis) to 100% (S. pneumoniae) at the post-therapy visit. All but one of the 265 patients who were cured or improved at post-therapy returned for a long-term follow-up visit; 243 (92%) remained well 4 to 6 weeks after therapy; and 21 (8%) had a relapse of symptoms. Adverse events considered to be related to levofloxacin administration were reported by 29 patients (9%). The most common drug-related adverse events were diarrhea, flatulence, and nausea; most adverse events were mild to moderate in severity.

CONCLUSION

The results of this study indicate that levofloxacin 500 mg once daily is an effective and safe treatment for acute bacterial sinusitis.

Levofloxacin and sparfloxacin: new quinolone antibiotics

OBJECTIVE

To discuss the pharmacology, pharmacokinetics, spectrum of activity, clinical trials, and adverse effects of levofloxacin and sparfloxacin, two new fluoroquinolone antibiotics.

DATA SOURCES

Literature was identified by a MEDLINE search from January 1985 to September 1997. Abstracts and presentations were identified by review of program abstracts from the Interscience Conference on Antimicrobial Agents and Chemotherapy from 1988 to 1996.

STUDY SELECTION

Randomized, controlled clinical studies were selected for evaluation; however, uncontrolled studies were included when data were limited for indications approved by the Food and Drug Administration (FDA). In vitro data were selected from comparison trials whenever available. Only in vitro trials that provided data on the minimum inhibitory concentrations required to inhibit 90% of isolates were used. Data from North American studies were selected whenever available.

DATA EXTRACTION

Data were evaluated with respect to in vitro activity, study design, clinical and microbiologic outcomes, and adverse drug reactions.

DATA SYNTHESIS

Levofloxacin and sparfloxacin are active against pathogens frequently involved in community-acquired upper and lower respiratory tract infections, including Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Mycoplasma pneumoniae, Legionella pneumophila, and Chlamydia pneumoniae. Both compounds have enhanced activity compared with ciprofloxacin against most gram-positive bacteria, including enterococci, streptococci, and staphylococci, and retain good activity against most Enterobacteriaceae and Pseudomonas aeruginosa. Sparfloxacin has greater anaerobic activity than levofloxacin, which is more active than ciprofloxacin or ofloxacin. Although many clinical studies are available only in abstract form, the clinical data demonstrate that these new quinolones are effective for most community-acquired upper and lower respiratory tract infections, urinary tract infections, gonococcal and nongonococcal urethritis, and skin and skin structure infections. FDA-approved indications are limited for both compounds to date.

CONCLUSIONS

Levofloxacin and sparfloxacin have improved gram-positive activity compared with that of older fluoroquinolones, and are administered once daily. Sparfloxacin-associated photosensitivity may limit its therapeutic usefulness. Clinical trials confirm that these agents are as effective as traditional therapies for the management of community-acquired pneumonia, acute exacerbations of chronic bronchitis, sinusitis, urinary tract infections, acute gonococcal and nongonococcal urethritis, and skin and skin structure infections.

Timed kill kinetic studies of levofloxacin, ofloxacin, and ciprofloxacin against Moraxella catarrhalis

Levofloxacin bactericidal activity was compared to ciprofloxacin and ofloxacin against 10 strains of Moraxella catarrhalis. The cidal action (by kill-curve analysis) was slightly more rapid for levofloxacin, but all tested fluoroquinolones were considered bactericidal for all strains tested, including those producing BRO-1 and 2 beta-lactamases.

Levofloxacin versus ciprofloxacin, flucloxacillin, or vancomycin for treatment of experimental endocarditis due to methicillin-susceptible or -resistant Staphylococcus aureus

Levofloxacin is the L isomer of ofloxacin, a racemic mixture in which the L stereochemical form carries the antimicrobial activity. Levofloxacin is more active than former quinolones against gram-positive bacteria, making it potentially useful against such pathogens. In this study, levofloxacin was compared to ciprofloxacin, flucloxacillin, and vancomycin for the treatment of experimental endocarditis due to two methicillin-susceptible Staphylococcus aureus (MSSA) and two methicillin-resistant S. aureus (MRSA) isolates. The four test organisms were susceptible to ciprofloxacin, the levofloxacin MICs for the organisms were low (0.12 to 0.25 mg/liter), and the organisms were killed in vitro by drug concentrations simulating both the peak and trough levels achieved in human serum (5 and 0.5 mg/liter, respectively) during levofloxacin therapy. Rats with aortic endocarditis were treated for 3 days. Antibiotics were injected with a programmable pump to simulate the kinetics of either levofloxacin (350 mg orally once a day), ciprofloxacin (750 mg orally twice a day), flucloxacillin (2 g intravenously four times a day), or vancomycin (1 g intravenously twice a day). Levofloxacin tended to be superior to ciprofloxacin in therapeutic experiments (P = 0.08). More importantly, levofloxacin did not select for resistance in the animals, in contrast to ciprofloxacin. The lower propensity of levofloxacin than ciprofloxacin to select for quinolone resistance was also clearly demonstrated in vitro. Finally, the effectiveness of this simulation of oral levofloxacin therapy was at least equivalent to that of standard treatment for MSSA or MRSA endocarditis with either flucloxacillin or vancomycin. This is noteworthy, because oral antibiotics are not expected to succeed in the treatment of severe staphylococcal infections. These good results obtained with animals suggest that levofloxacin might deserve consideration for further study in the treatment of infections due to ciprofloxacin-susceptible staphylococci in humans.

Assessment of the synergistic interactions of levofloxacin and ampicillin against Enterococcus faecium by the checkerboard agar dilution and time-kill methods

Multidrug-resistant enterococci have become increasingly difficult to eradicate in a growing number of nosocomial infections. With the emergence of vancomycin-resistant enterococci, the use of synergistic antibiotic combinations has become one of the only remaining therapeutic options. Levofloxacin, the active l-isomer of ofloxacin, is a new oral and intravenous fluoroquinolone with a broad spectrum of activity against numerous Gram-positive, Gram-negative, and atypical organisms. The in vitro activity of levofloxacin, alone and in combination with ampicillin, against recent clinical isolates of Enterococcus faecium was assessed for synergistic interactions using the checkerboard agar dilution technique and time-kill methodology. Against all strains, the static technique of checkerboard agar dilution demonstrated indifferent or additive effects for the ampicillin + levofloxacin combination. With the dynamic time-kill technique, synergy was demonstrated for ampicillin (16 micrograms/ml) + levofloxacin (2 micrograms/ml) combination against three levofloxacin-sensitive, ampicillin-resistant isolates. At 24 h, the combination yielded a > or = 2-log10 decrease in CFU/ml compared to levofloxacin alone, while ampicillin had negligible effects. Against both a levofloxacin-intermediate, ampicillin-resistant isolate, and a highly levofloxacin-resistant, ampicillin-resistant isolate, none of the ampicillin+levofloxacin combinations tested demonstrated a synergistic interaction. The time-kill method suggested synergy for the ampicillin+levofloxacin combination against some strains of E. faecium.