a Department of Medical Microbiology, City Hospital NHS Trust, Birmingham, UK b Department of Thoracic Medicine, City Hospital NHS Trust, Birmingham, UK
Abstract
The concentrations of clinafloxacin were measured in serum, bronchial mucosa, alveolar macrophages and epithelial lining fluid after single 200 mg oral doses of clinafloxacin had been administered to 15 subjects who were undergoing bronchoscopy. Concentrations were measured using a microbiological assay method. Mean concentrations in serum, bronchial mucosa, alveolar macrophages and epithelial lining fluid at a mean of 1.27 h post-dose were 1.54, 2.65, 15.60 and 2.71 mg/L respectively. These site concentrations exceeded the MIC90 for common respiratory pathogens and indicate that clinafloxacin is likely to be effective in the treatment of a wide range of respiratory tract infections.
Introduction
Clinafloxacin (CI-960, PD 127391) is a fluoroquinolone antibacterial agent with a broad spectrum of activity. Compared with other available quinolones, clinafloxacin usually requires lower drug concentrations for bacterial inhibition and is active against a broad range of organisms including Gram-negative and -positive bacteria and strict anaerobes. Enterococcus faecalis and Pseudomonas aeruginosa are sensitive to clinafloxacin in vitro. 1,2 Clinofloxacin has an elimination half life of 57 h and a large volume of distribution. 3
This study was designed to assess concentrations of clinafloxacin in lung tissues with simultaneous measurement of serum levels after administration of single 200 mg oral doses.
Patients and methods
Fifteen patients (eight male and seven female) undergoing diagnostic fibre-optic bronchoscopy were enrolled into the study. All subjects were over 17 years of age and all female subjects were post-menopausal. All subjects gave fully informed, written consent and the study was approved by the Hospital Ethics Committee. Patients were excluded from the study if they had active lung infection, were on any antimicrobial agent, if they weighed <45 kg or if they had any unstable medical condition. Patients were also excluded from the study if they had any significant renal or hepatic disease or if they had a history of allergy to quinolones.
All potential subjects were screened within 14 days prior to bronchoscopy. This screening procedure included a detailed medical history, physical examination and blood analyses for haematology and clinical chemistry. The subjects received a single oral dose of 200 mg of clinafloxacin on the day of bronchoscopy after having fasted for 4 h. Bronchoscopy was carried out between 0.9 and 2 h post-dose. At bronchoscopy, as well as diagnostic samples, bronchial mucosal samples were taken and broncho-alveolar lavage (BAL) was performed. The lavage was carried out using four 50 mL aliquots of pre-warmed saline followed by gentle aspiration. The aspirate from the first 50 mL of lavage was discarded to avoid contamination with proximal airway contents. The aspirates from the next three aliquots were pooled and then placed in two Teflon containers; samples were then processed using a previously described method. 4
Microbiological assay
Assay plates containing Iso-Sensitest agar (Oxoid, Basingstoke, UK) were surface flooded with Escherichia coli 4004 (Bayer AG, Leverkusen, Germany) diluted to an optical density of 0.04 at a wavelength of 630 nm. Wells of 5 mm diameter were then punched into the agar and samples (comprising tests, calibrators, internal controls and quality assurance samples) were applied in triplicate in a random pattern. Calibrators, internal controls and quality assurance samples were prepared in human serum (Bradsure Biologicals, Loughborough, UK), pH 7 phosphate buffer and 9% sodium chloride for the assay of serum, macrophages and biopsies and BAL samples respectively. Calibrator ranges were 0.125, 0.25, 0.5, 1 and 2 mg/L for serum and 0.008, 0.015, 0.031, 0.062 and 0.125 mg/L for macrophages, biopsy and BAL samples.
Internal controls were 1.5 and 0.2 mg/L for serum, and 0.1 and 0.01 mg/L for all other samples. Plates were incubated overnight at 30°C and diameters of the zones of inhibition were then measured using an image analyser (Imaging Associates, Thame, UK). A line of best fit was calculated using Bennett's calculation. 5
The concentrations of antibiotic in bronchial mucosal biopsies, macrophages and epithelial lining fluid (ELF) were calculated as previously described.4
Results
Coefficients of variation for internal controls at concentrations of 1.5 and 0.2 mg/L in serum, pH 7 phosphate buffer and 0.1 and 0.01 mg/L in 9% sodium chloride were 6.0 and 5.1, 6.5 and 7.3, and 7.1 and 6.8% respectively.
The times of bronchoscopy ranged from 0.9 to 1.95 h post-dose. The Table shows the levels of clinafloxacin in serum and tissues in individual subjects and mean (S.D.) values.
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This single-dose study has shown that clinafloxacin concentrations in ELF, alveolar cells and bronchial mucosa were comparable to those in serum. The mean levels achieved at these sites exceeded the MIC90 values for a wide range of respiratory pathogens. The MIC90 values (mg/L) for clinafloxacin against respiratory pathogens are 0.12 for Streptococcus pneumoniae, 0.008 for Haemophilus influenzae, 0.015 for Legionella pneumophila, 0.03 for Staphylococcus aureus and 0.5 for P. aeruginosa. 1, 6This low level of MIC90 is particularly important with regard to S. pneumoniae where the MIC90 of earlier quinolones (e.g. ciprofloxacin MIC90 2 mg/L ) was higher than that for clinafloxacin.7
The mean bronchial mucosa:serum ratio of 1.72 for clinafloxacin was similar to that for other quinolones; however, theELF:serum ratio, 1.76, was slightly lower, possibly due to sampling in an earlier time-frame. 4,8 The excellent penetration of quinolones into alveolar macrophages was again confirmed in this study. It has been reported, however, that site:serum ratios may be even higher after multiple dosing of quinolones,4 presumably due to tissue accumulation.
Following oral administration to healthy human subjects, Cmax is achieved within 2 h, with linear pharmacokinetics in the 25 400 mg single-dose range.
The results of our study suggest that clinafloxacin should be effective in a wide range of respiratory infections. Clinafloxacin is present in these lung sites at concentrations well in excess of the MIC90 (i.e. 0.12 mg/L) to S. pneumoniae. 1, 2 Increasing ß-lactam and macrolide resistance of S. pneumoniaeis of major concern and the potential value of newer quinolones in this area is of interest.
Acknowledgments
We thank Parke-Davis for financial support for this project.
References
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Received 4 March 1998; returned 6 May 1998; revised 17 June 1998; accepted 3 August 1998