A new dosing paradigm: High-dose, short-course fluoroquinolone therapy for community-acquired pneumonia

Short-Course Therapy of Gemifloxacin Effective Against Pneumococcal Pneumonia in Mice

Standard 7-14 day (d) courses of antimicrobial therapy for community-acquired pneumonia (CAP) are thought to have contributed to the emergence of resistant pneumoccoci. Consequently, short-course fluoroquinolone regimens have been proposed to minimize resistance. To test this, we examined 2-day versus 5-day regimens of gemifloxacin and levofloxacin for treatment of pneumonia in a murine model. In doing so, we also investigated whether the enhanced potency of gemifloxacin would influence outcomes. CD1 Swiss mice were infected intratracheally with 10(5)-CFU of a virulent Streptococcus pneumoniae strain. Drugs were administered every 8 h for 2 d and 5 d, starting at 24 h postinfection. Temperature was used to assess disease progression. Gemifloxacin remained effective for 2 d and 5 d, with survival rates of 100%-83% compared with 40%-58% for levofloxacin. Eighty-nine to 100% of gemifloxacin-treated mice were clear of pulmonary bacteria compared with only 0%-20% for levofloxacin. For levofloxacin-treated mice, 2 of 7 (29%) isolates with a levofloxacin minimum inhibitory concentration (MIC) 4 times that of the infecting parent strain had ParC mutations. By contrast, no isolates recovered from gemifloxacin-treated mice were reduced in susceptibility. Gemifloxacin could be effective in shortening duration of therapy for CAP treatment as well as minimize resistance development.

Antibiotics in acute exacerbations of chronic bronchitis

Acute exacerbations of chronic bronchitis (AECB) are a major contributor to morbidity and mortality in patients with chronic obstructive pulmonary disease, accounting for more than 16 million physician office visits and over 500,000 hospitalizations in the USA each year. Antimicrobials have been recognized by clinical guidelines as an important component in the management of AECB with a bacterial etiology. The challenge of identifying patients most likely to benefit from antimicrobial therapy is difficult in the clinical setting. However, appropriate risk stratification of patients, and the use of antimicrobials within the correct spectrum and for a suitable duration, can improve clinical outcomes while minimizing induction of antimicrobial resistance. With an improved design in pharmacologic and clinical studies, differences can be appreciated among the various antimicrobial agents available to treat AECB. Factors to be considered in antimicrobial agent selection include local tissue penetration, effects on bacteriological eradication, duration of therapy, speed of resolution and prevention or delay of recurrences.

Intrapulmonary pharmacodynamics of high-dose levofloxacin in subjects with chronic bronchitis or chronic obstructive pulmonary disease

The objective of this study was to determine the plasma and intrapulmonary pharmacokinetic parameters of intravenously administered levofloxacin in subjects with stable chronic lung disease. Three doses of 1000 mg levofloxacin were administered once daily to 16 adult subjects divided into four groups of 4 subjects each. Standardised bronchoscopy and timed bronchoalveolar lavage (BAL) were performed at 4 h, 8 h, 12 h and 24 h following administration of the last dose. Blood was obtained for drug assay prior to drug administration, at the end of the last infusion (maximum concentration (Cmax)) and at the time of BAL. Levofloxacin was measured using a high-performance liquid chromatographic tandem mass spectrometric (HPLC/MS/MS) technique. Plasma, epithelial lining fluid (ELF) and alveolar cell (AC) pharmacokinetics were derived using non-compartmental methods. Cmax/MIC(90) and area under the concentration-time curve for 0-24 h after the last dose (AUC(0-24 h)/MIC(90) ratios were calculated for respiratory pathogens with minimum inhibitory concentrations for 90% of the organisms (MIC(90)) of 0.03-2 microg/mL. The Cmax (mean+/-standard deviation), AUC(0-24h) and half-life were, respectively, 9.2+/-2.7 microg/mL, 130 microg h/mL and 8.7 h for plasma, 22.8+/-12.9 microg/mL, 260 microg h/mL and 7.0 h for ELF and 76.3+/-28.7 microg/mL, 1492 microg h/mL and 49.5 h for ACs. Levofloxacin concentrations were quantitatively greater in ACs than in ELF or plasma at all time points, however only the differences between AC concentration and ELF or plasma concentrations in the 4-h and 8-h time groups were statistically significant. Cmax/MIC(90) and AUC/MIC(90) ratios in ELF were, respectively, 11.4 and 130 for Mycoplasma pneumoniae, 22.8 and 260 for Streptococcus pneumoniae, 91.2 and 1040 for Chlamydia pneumoniae and 760 and 8667 for Haemophilus influenzae. In ACs the ratios were 38.2 and 746 for M. pneumoniae, 76.3 and 1492 for S. pneumoniae, 305 and 5968 for C. pneumoniae and 2543 and 49 733 for H. influenzae. In conclusion, Cmax/MIC(90) and AUC/MIC(90) ratios provide a pharmacokinetic rationale for once-daily administration of a 1000 mg dose of levofloxacin and are favourable for the treatment of respiratory infection in patients with chronic lung disease.

Principles of Antimicrobial Therapy

The most compelling reason for practicing judicious antimicrobial use is to facilitate therapeutic success. The definition of therapeutic success has changed in recent years, however; not only does success include eradication of infection, but it must now include avoidance of resistance. If the goal of antimicrobial therapy is to achieve sufficient concentrations at the site of infection such that the infecting organism is killed, therapy should be successful.

Intrapulmonary pharmacokinetics and pharmacodynamics of high-dose levofloxacin in healthy volunteer subjects

The objective of this study was to determine the plasma and intrapulmonary pharmacokinetic parameters of intravenously administered levofloxacin in healthy volunteers. Three doses of either 750 mg or 1000 mg levofloxacin were administered intravenously to 4 healthy adult subjects (750 mg) to 20 healthy adult subjects divided into five groups of 4 subjects (1000 mg). Standardised bronchoscopy and timed bronchoalveolar lavage (BAL) were performed following administration of the last dose. Blood was obtained for drug assay prior to drug administration and at the time of BAL. Levofloxacin was measured in plasma, BAL fluid and alveolar cells (ACs) using a sensitive and specific combined high-performance liquid chromatographic tandem mass spectrometric technique (HPLC/MS/MS). Plasma, epithelial lining fluid (ELF) and AC pharmacokinetics were derived using non-compartmental methods. The maximum plasma drug concentration to minimum inhibitory concentration ratio (C(max)/MIC(90)) and the area under the drug concentration curve to minimum inhibitory concentration ratio (AUC/MIC(90)) during the dosing interval were calculated for potential respiratory pathogens with MIC(90) values from 0.03 microg/mL to 2 microg/mL. In the 1000 mg dose group, the C(max) (mean+/-standard deviation (S.D.)), AUC(0-8h) and half-life were: for plasma, 9.2+/-1.9 microg/mL, 103.6 microg h/mL and 7.45 h; for ELF, 25.8+/-7.9 microg/mL, 279.1 microg h/mL and 8.10h; and for ACs, 51.8+/-26.2 microg/mL, 507.5 microg h/mL and 14.32 h. In the 750 mg dose group, the C(max) values in plasma, ELF and ACs were 5.7+/-0.4, 28.0+/-23.6 and 34.2+/-18.7 microg/mL, respectively. Levofloxacin concentrations were significantly higher in ELF and ACs than in plasma at all time points. For pathogens commonly associated with community-acquired pneumonia, C(max)/MIC(90) ratios in ELF ranged from 12.9 for Mycoplasma pneumoniae to 859 for Haemophilus influenzae, and AUC/MIC(90) ratios ranged from 139 to 9303, respectively. The C(max)/MIC(90) ratios in ACs ranged from 25.9 for M. pneumoniae to 1727 for H. influenzae, and AUC/MIC(90) ratios ranged from 254 to 16917, respectively. The C(max)/MIC(90) and AUC/MIC(90) ratios provide a pharmacokinetic rationale for once-daily administration of a 1000 mg dose of levofloxacin and are favourable for the treatment of community-acquired respiratory pathogens.

Principles of antibiotic treatment of community-acquired pneumonia in the outpatient setting

Community-acquired pneumonia (CAP) is a common illness with high rates of morbidity and mortality. Nearly 80% of the treatment for this condition is provided in the outpatient setting. Among the etiologic agents associated with bacterial CAP, the predominant pathogen is Streptococcus pneumoniae. Treatment of CAP for the most part is empirical; therefore, any antibiotic treatment should cover both typical and atypical pathogens. The beta-lactams have historically been considered standard therapy for the treatment of CAP. However, the impact of rising resistance rates is now a primary concern facing physicians. For patients with comorbidities or recent antibiotic therapy, current guidelines recommend either combination therapy with a beta-lactam and a macrolide or an antipneumococcal fluoroquinolone alone. Fluoroquinolones are broad-spectrum antibiotics that exhibit high levels of penetration into the lungs and low levels of resistance. Evidence from clinical trials indicates clinical success rates of > 90% for moxifloxacin, gatifloxacin, and levofloxacin in the treatment of CAP due to S pneumoniae. Data from comparative clinical trials suggest fluoroquinolone monotherapy is as efficacious as beta-lactam-macrolide combination therapy in the treatment of CAP patients. The respiratory fluoroquinolone levofloxacin has also been shown to be effective in CAP patients for the treatment of macrolide-resistant S pneumoniae. The use of azithromycin, telithromycin, and fluoroquinolones in short-course regimens has been shown to be efficacious, safe, and tolerable in patients with CAP. Based on clinical evidence, high-dose, short-course therapies may represent a significant advance in the management of CAP.

Appropriate outpatient treatment of acute bacterial exacerbations of chronic bronchitis

Acute exacerbations of chronic bronchitis (AECB), which are characteristic of chronic obstructive pulmonary disease (COPD), contribute to morbidity and decreased quality of life for patients with COPD. A significant proportion of these exacerbations are due to bacterial infections. The Council for Appropriate and Rational Antibiotic Therapy (CARAT) criteria provide guidance for choosing the optimal drug at its optimal dose and duration for antimicrobial treatment of AECB due to bacterial infection. Evidence-based guidelines recommend stratifying patients according to risk factors to improve selection of targeted antimicrobial therapy. With increasing rates of resistance to some antimicrobials, resistance is also an important consideration for reducing treatment failures and decreasing the need for further pharmacologic treatment. Fluoroquinolones are recommended as first-line therapy for patients with chronic bronchitis who have risk factors; gatifloxacin, gemifloxacin, and levofloxacin are highly active against commonly encountered pathogens. Safety profiles are an important consideration because adverse events and poor tolerability can reduce patient adherence rates, which in turn can lead to poorer outcomes. Safety profiles also become an important consideration as shorter-course, higher-dose therapies become more prevalent. First-line therapy with a well-tolerated antibiotic that is active against the predominant pathogens, combined with low resistance rates and a convenient once-a-day dosing regimen, may reduce overall costs. Fluoroquinolones exhibit low resistance, good activity levels, and high respiratory penetration, and they are particularly well suited for shorter-course, higher-dose regimens in selected patients. Shorter-course, higher dose regimens, in turn, may be more effective, cost-efficient, and appropriate for controlling the rise of resistance than standard regimens.

Antimicrobial treatment of lower respiratory tract infections in the hospital setting

Respiratory tract infections (RTIs) that may require hospitalization include acute exacerbations of chronic bronchitis (AECB), community-acquired pneumonia (CAP), and hospital-acquired pneumonia (HAP), which includes ventilator-associated pneumonia (VAP). Healthcare-associated pneumonia (HCAP) is treated similar to HAP and may be considered with HAP. For CAP requiring hospitalization, the current guidelines for the treatments of RTIs generally recommend either a beta-lactam and macrolide combination or a fluoroquinolone. The respiratory fluoroquinolones (levofloxacin, gatifloxacin, moxifloxacin, and gemifloxacin) are excellent antibiotics due to high levels of susceptibility among gram-negative, gram-positive, and atypical pathogens. The fluoroquinolones are active against > 98% of Streptococcus pneumoniae, including penicillin-resistant strains. Fluoroquinolones are also recommended for AECB requiring hospitalization. Evidence from clinical trials suggests that levofloxacin monotherapy is as efficacious as combination ceftriaxone-erythromycin therapy in the treatment of patients hospitalized with CAP. For early-onset HAP, VAP, and HCAP without the risk of multidrug resistance, ceftriaxone, ampicillin-sulbactam, ertapenem, or one of the fluoroquinolones is recommended. High-dose, short-course therapy regimens may offer improved treatment due to higher drug concentrations, more rapid killing, increased adherence, and the potential to reduce development of resistance. Recent studies have shown that short-course therapy with levofloxacin, azithromycin, or telithromycin in patients with CAP was effective, safe, and tolerable and may control the rate of resistance.

Treatment of rhinosinusitis in the outpatient setting

Rhinosinusitis is one of the most common respiratory tract conditions seen by primary care physicians. Each year approximately 20 million cases of acute bacterial rhinosinusitis (ABRS) occur in the United States. Since diagnosis of ABRS relies on clinical evaluation, treatments are usually empirical and include an antibiotic treatment that covers the common bacteria associated with ABRS infection, Streptococcus pneumoniae and Haemophilus influenzae. The Council for Appropriate and Rational Antibiotic Therapy (CARAT) recommends that antimicrobial therapy for rhinosinusitis should combine high susceptibility, clinical effectiveness, safety, and tolerability. The most efficacious antibiotics for ABRS include the respiratory fluoroquinolones gatifloxacin, levofloxacin, and moxifloxacin, as well as ceftriaxone and amoxicillin-clavulanate. The use of fluoroquinolones or high-dose amoxicillin-clavulanate is recommended for patients with mild disease who have had recent antimicrobial therapy or for patients with moderate disease. These drugs are generally well tolerated with mild adverse effects. Resistance to fluoroquinolones in S pneumoniae and H influenzae has remained low in spite of their increased use. Recent studies indicate that short-course, high-dose treatment regimens may reduce total drug use, improve tolerability and adherence, prevent increases in resistance, and increase efficacy. The use of fluoroquinolones or amoxicillin-clavulanate in a short-course, high-dose regimen may represent an exciting new protocol in the treatment of rhinosinusitis.