Pulmonary disposition of roxithromycin (RU 28965), a new macrolide antibiotic

Oral antibiotics used in the treatment of chronic rhinosinusitis have limited penetration into the sinonasal mucosa: a randomized trial

Despite the widespread prescription of antibiotics for patients with chronic rhinosinusitis (CRS), the extent to which drug distribution to the sinonasal mucosa occurs remains largely undefined. Twenty subjects undergoing functional endoscopic sinus surgery (FESS) for CRS were randomized to one of two groups: 1) doxycycline (100 mg daily for seven days) 2) roxithromycin (300 mg daily for seven days). Drug levels were measured using liquid chromatography-tandem mass spectrometry in sinonasal mucus, sinonasal tissues and serum at steady state. Doxycycline concentrations measured in the mucus were significantly lower compared to that in the serum (mean mucus/serum ratio = 0.16, p < 0.001) and the tissue (mean mucus/tissue ratio = 0.18, p < 0.0001). Roxithromycin concentrations in the mucus were also significantly lower compared to that in the serum (mean mucus/serum ratio = 0.37, p = 0.002) and the tissue (mean mucus/tissue ratio = 0.60, p < 0.001). Although the efficacy of doxycycline and roxithromycin in sinonasal mucus in vivo cannot be predicted solely from reported minimum inhibitory concentrations, given the added complexity of bacterial biofilm antimicrobial tolerance, these results suggest that low mucosal penetration of antibiotics may be one of the factors contributing to the limited efficacy of these agents in the treatment of CRS.

Measurements of Deposition, Lung Surface Area and Lung Fluid for Simulation of Inhaled Compounds

Modern strategies in drug development employ in silico techniques in the design of compounds as well as estimations of pharmacokinetics, pharmacodynamics and toxicity parameters. The quality of the results depends on software algorithm, data library and input data. Compared to simulations of absorption, distribution, metabolism, excretion, and toxicity of oral drug compounds, relatively few studies report predictions of pharmacokinetics and pharmacodynamics of inhaled substances. For calculation of the drug concentration at the absorption site, the pulmonary epithelium, physiological parameters such as lung surface and distribution volume (lung lining fluid) have to be known. These parameters can only be determined by invasive techniques and by postmortem studies. Very different values have been reported in the literature. This review addresses the state of software programs for simulation of orally inhaled substances and focuses on problems in the determination of particle deposition, lung surface and of lung lining fluid. The different surface areas for deposition and for drug absorption are difficult to include directly into the simulations. As drug levels are influenced by multiple parameters the role of single parameters in the simulations cannot be identified easily.

Pharmacokinetics of arbekacin in bronchial epithelial lining fluid of healthy volunteers

INTRODUCTION

Arbekacin is a unique aminoglycoside antibiotic with anti-methicillin-resistant Staphylococcus aureus activity. The efficacy of aminoglycosides is related to their serum maximum concentration. Local concentration of antibiotics in pulmonary epithelial lining fluid, rather than its serum concentration, can help determine its clinical efficacy more precisely for treatment of respiratory infectious disease. The objective of this study was to sequentially measure arbekacin concentration in epithelial lining fluid after infusion of a single clinically available dose.

METHOD

After the initial blood sampling, arbekacin was intravenously infused into 6 healthy volunteers over 1 h. Epithelial lining fluid and serum samples were collected by bronchoscopic microsampling 1, 1.5, 2, 2.5, 3, 4, 5, and 6 h after the start of 200 mg arbekacin infusion.

RESULTS

Each probe sampled 10.1 ± 5.2 μl bronchial epithelial lining fluid. The sample dilution factor was 266.7 ± 157.1. Drug concentration was successfully measured in all but 2 of the epithelial lining fluid samples. The maximum concentration of arbekacin in epithelial lining fluid and serum was 10.4 ± 1.9 μg/ml and 26.0 ± 12.2 μg/ml, respectively. The ratio of the maximum drug concentration in the epithelial lining fluid to that in the serum was 0.47 ± 0.19.

CONCLUSIONS

The maximum concentration of epithelial lining fluid reached levels that would effectively treat most clinical strains of methicillin-resistant S. aureus.

Delivering Antibacterials to the Lungs

An important determinant of clinical outcome of a lower respiratory tract infection may be sterilization of the infected lung, which is also dependent on sustained antibacterial concentrations achieved in the lung. For this reason, recently there has been increased interest in measuring the concentration of antimicrobial agents at different potential sites of infection in the lung. Levels of antibacterials are now measured in bronchial mucosa, epithelial lining fluid (ELF) and alveolar macrophages, as well as in sputum. Penicillins and cephalosporins reach only marginal concentrations in bronchial secretions, whereas fluoroquinolones and macrolides have been shown to achieve high concentrations. The extent of penetration of different antibacterials into the bronchial mucosa is relatively high. This is also true for beta-lactams, although their tissue concentrations never reach blood concentrations. Antibacterials penetrate less into the ELF than into the bronchial mucosa, but fluoroquinolones appear to concentrate more into alveolar lavage than into bronchial mucosa. Pulmonary pharmacokinetics is a very useful tool for describing how drugs behave in the human lung, but it does not promote an understanding of the pharmacological effects of a drug. More important, instead, is the correlation between pulmonary disposition of the drug and its minimum inhibitory concentration (MIC) values for the infectious agent. The addition of bacteriological characteristics to in vivo pharmacokinetic studies has triggered a 'pharmacodynamic approach'. Pharmacodynamic parameters integrate the microbiological activity and pharmacokinetics of an anti-infective drug by focusing on its biological effects, particularly growth inhibition and killing of pathogens. Drugs that penetrate well and remain for long periods at the pulmonary site of infection often induce therapeutic responses greater than expected on the basis of in vitro data. However, although the determination of antibacterial concentrations at the site of infection in the lung has been suggested to be important in predicting the therapeutic efficacy of antimicrobial treatment during bacterial infections of the lower respiratory tract, some studies have demonstrated that pulmonary bacterial clearance is correlated more closely to concentrations in the serum than to those in the lung homogenates, probably because they better reflect antibacterial concentration in the interstitial fluid.

Penetration of anti-infective agents into pulmonary epithelial lining fluid: focus on antibacterial agents

The exposure-response relationship of anti-infective agents at the site of infection is currently being re-examined. Epithelial lining fluid (ELF) has been suggested as the site (compartment) of antimicrobial activity against lung infections caused by extracellular pathogens. There have been an extensive number of studies conducted during the past 20 years to determine drug penetration into ELF and to compare plasma and ELF concentrations of anti-infective agents. The majority of these studies estimated ELF drug concentrations by the method of urea dilution and involved either healthy adult subjects or patients undergoing diagnostic bronchoscopy. Antibacterial agents such as macrolides, ketolides, newer fluoroquinolones and oxazolidinones have ELF to plasma concentration ratios of >1. In comparison, β-lactams, aminoglycosides and glycopeptides have ELF to plasma concentration ratios of ≤1. Potential explanations (e.g. drug transporters, overestimation of the ELF volume, lysis of cells) for why these differences in ELF penetration occur among antibacterial classes need further investigation. The relationship between ELF concentrations and clinical outcomes has been under-studied. In vitro pharmacodynamic models, using simulated ELF and plasma concentrations, have been used to examine the eradication rates of resistant and susceptible pathogens and to explain why selected anti-infective agents (e.g. those with ELF to plasma concentration ratios of >1) are less likely to be associated with clinical treatment failures. Population pharmacokinetic modelling and Monte Carlo simulations have recently been used and permit ELF and plasma concentrations to be evaluated with regard to achievement of target attainment rates. These mathematical modelling techniques have also allowed further examination of drug doses and differences in the time courses of ELF and plasma concentrations as potential explanations for clinical and microbiological effects seen in clinical trials. Further studies are warranted in patients with lower respiratory tract infections to confirm and explore the relationships between ELF concentrations, clinical and microbiological outcomes, and pharmacodynamic parameters.

Antimicrobial chemotherapy and lung microdialysis: a review

Pneumonia is a form of lung infection that may be caused by various micro-organisms. The predominant site of infection in pneumonia is debatable. Advances in the fields of diagnostic and therapeutic medicine have had a less than optimal effect on the outcome of pneumonia and one of the many causes is likely to be inadequate antimicrobial concentrations at the site of infection in lung tissue. Traditional antimicrobial therapy guidelines are based on indirect modelling from blood antimicrobial levels. However, studies both in humans and animals have shown the fallacy of this concept in various tissues. Many different methods have been employed to study lung tissue antimicrobial levels with limited success, and each has limitations that diminish their utility. An emerging technique being used to study the pharmacokinetics of antimicrobial agents in lung tissue is microdialysis. Development of microdialysis catheters, along with improvement in analytical techniques, has improved the accuracy of the data. Unfortunately, very few studies have reported the use of microdialysis in lung tissue, and even fewer antimicrobial classes have been studied. These studies generally suggest that this technique is a safe and effective way of assessing the pharmacokinetics of antimicrobial agents in lung tissue. Further descriptive studies need to be conducted to study the pharmacokinetics and pharmacodynamics of different antimicrobial classes in lung tissue. Data emanating from these studies could inform decisions for appropriate dosing schedules of antimicrobial agents in pneumonia.

Beneficial effect of antibiotics on ciliary beat frequency of human nasal epithelial cells exposed to bacterial toxins

In the present study, we explored whether the cilio-inhibitory effect induced by toxins derived from bacterial infections could be compensated for by a cilio-stimulatory effect of antibiotics. Human nasal epithelial cells (HNEC) expressing beating cilia were grown as monolayers. Ciliary beat frequency (CBF) was determined using an inverted microscope coupled with a high-speed digital camera. Clarithromycin and neomycin did not influence ciliary activity. Bacitracin, clindamycin, gramicidin and roxithromycin increased CBF significantly: by 50 +/- 12%, 54 +/- 16%, 31 +/- 16% and 31 +/- 18%, respectively. A 30 min exposure to Staphylococcus aureus enterotoxin B (SEB) and Pseudomonas aeruginosa lipopolysaccharide (PAL) decreased CBF significantly, by 37 +/- 16 and 28 +/- 12%, respectively. In contrast with exposure to the toxin alone, co-incubation of the nasal monolayer cells with PAL and bacitracin or clindamycin did not result in a decrease in CBF after 30 and 60 min. The effect of SEB could be compensated for by bacitracin but not by clindamycin. After a 12 h preincubation period with SEB, co-incubation with either bacitracin or clindamycin resulted in the complete recovery of CBF. This study suggests that topical antibiotic treatment of nasal infections could result in a dual positive effect, namely treatment of the bacterial infection and recovery of ciliary activity.

[Blood and respiratory diffusion of antibiotics. A critical analysis of predictive parameters for clinical effectiveness]

The implementation of a treatment for lower respiratory tract infections must integrate a pharmacokinetic/pharmacodynamic (PK-PD) approach of antibiotic dosing. The activity of beta-lactam antibiotics is best predicted by the duration of time during which serum concentrations exceed the MIC (T>MIC). T>MIC of 30-40% is sufficient to achieve clinical cure in immunocompetent patients. This threshold is achieved with amoxicillin for penicillin susceptible or resistant Sreptococcus pneumoniae and with amoxicillin-clavulanate and ceftriaxone for S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. For macrolides, the activity is best predicted by T>MIC and for azithromycin and telithromycin by area-under-the-curve/MIC (AUC/MIC). Sufficient PK-PD values are only achieved for macrolides against susceptible strains of S. pneumoniae and against M. catarrhalis; for telithromycin, an AUC/MIC>25, which is necessary for bacterial eradication, is achieved in>99% of patients for S. pneumoniae and M. catarrhalis and>90% of patients for H. influenzae. For fluoroquinolones, both peak/MIC and AUC/MIC are predictors of clinical and bacteriological efficacy. AUC/MIC required ratios vary according to pathogens and severity of diseases from 48 to 125. These thresholds are reached for respiratory pathogens; for S. pneumoniae, AUC/MIC90 ratios of levofloxacin and moxifloxacin are 96 and 192, respectively; the presence of a mutation in parC increases the risk for the acquisition of additional mutations and failure.

Bronchoscopic microsampling method for measuring drug concentration in epithelial lining fluid

Direct measurement of the concentration of antimicrobial agents in bronchial epithelial lining fluid (ELF) would allow for a more informed approach to appropriate dosing of antimicrobial agents for respiratory tract infections. In this study, we determined the time versus concentration profile in ELF after an oral administration of levofloxacin, using recently developed bronchoscopic microsampling probes. These probes could be repeatedly and safely inserted through the fiberoptic bronchoscope in normal healthy volunteers. The concentration of levofloxacin in ELF was 43.4% of the corresponding serum value at 1 hour, reached the same level at 2 hours, decreased in a similar manner as that in serum, and returned to undetectable levels at 24 hours. It exceeded minimal inhibitory concentrations of Staphylococcus aureus (0.25 microg/ml), Klebsiella species (0.5 microg/ml), and Haemophilus influenzae (0.06 microg/ml) after 6 hours. The experimental procedure was well tolerated, and no complications were observed. In conclusion, bronchoscopic microsampling is a feasible and promising method for measuring antimicrobial concentrations in the target sites of respiratory tracts directly and repeatedly.

Closed-chest microdialysis to measure antibiotic penetration into human lung tissue

The majority of bacterial lung infections are localized to the interstitial space fluid, which is therefore an important target site for antimicrobial chemotherapy. Direct measurement of interstitial concentrations of antimicrobial agents in human lung tissue would allow for a more informed approach to appropriate dosing of antimicrobial agents, but until now this was beyond technical reach. In this exploratory pharmacokinetic study, we measured the time versus concentration profile of cefpirome after a single intravenous dose administration of 2 g in the lung interstitial fluid by flexible microdialysis catheters, which were implanted during lung surgery for pulmonary tumors in five patients. Cefpirome concentrations in lung interstitial fluid were 66% of corresponding plasma values within the first 240 min, and exceeded minimal inhibitory concentrations of most relevant bacteria. The experimental procedure was well tolerated by the patients and no adverse events were observed. The present study provides evidence for the first time that closed chest microdialysis of the human lung is a feasible and safe method to measure lung concentrations in patients in vivo. The present data also corroborate the use of cefpirome as a valuable agent in the treatment of lung infections with most extracellular bacteria.

Review of macrolides and ketolides: focus on respiratory tract infections

The first macrolide, erythromycin A, demonstrated broad-spectrum antimicrobial activity and was used primarily for respiratory and skin and soft tissue infections. Newer 14-, 15- and 16-membered ring macrolides such as clarithromycin and the azalide, azithromycin, have been developed to address the limitations of erythromycin. The main structural component of the macrolides is a large lactone ring that varies in size from 12 to 16 atoms. A new group of 14-membered macrolides known as the ketolides have recently been developed which have a 3-keto in place of the L-cladinose moiety. Macrolides reversibly bind to the 23S rRNA and thus, inhibit protein synthesis by blocking elongation. The ketolides have also been reported to bind to 23S rRNA and their mechanism of action is similar to that of macrolides. Macrolide resistance mechanisms include target site alteration, alteration in antibiotic transport and modification of the antibiotic. The macrolides and ketolides exhibit good activity against gram-positive aerobes and some gram-negative aerobes. Ketolides have excellent activity versus macrolide-resistant Streptococcus spp. Including mefA and ermB producing Streptococcus pneumoniae. The newer macrolides, such as azithromycin and clarithromycin, and the ketolides exhibit greater activity against Haemophilus influenzae than erythromycin. The bioavailability of macrolides ranges from 25 to 85%, with corresponding serum concentrations ranging from 0.4 to 12 mg/L and area under the concentration-time curves from 3 to 115 mg/L x h. Half-lives range from short for erythromycin to medium for clarithromycin, roxithromycin and ketolides, to very long for dirithromycin and azithromycin. All of these agents display large volumes of distribution with excellent uptake into respiratory tissues and fluids relative to serum. The majority of the agents are hepatically metabolised and excretion in the urine is limited, with the exception of clarithromycin. Clinical trials involving the macrolides are available for various respiratory infections. In general, macrolides are the preferred treatment for community-acquired pneumonia and alternative treatment for other respiratory infections. These agents are frequently used in patients with penicillin allergies. The macrolides are well-tolerated agents. Macrolides are divided into 3 groups for likely occurrence of drug-drug interactions: group 1 (e.g. erythromycin) are frequently involved, group 2 (e.g. clarithromycin, roxithromycin) are less commonly involved, whereas drug interactions have not been described for group 3 (e.g. azithromycin, dirithromycin). Few pharmacoeconomic studies involving macrolides are presently available. The ketolides are being developed in an attempt to address the increasingly prevalent problems of macrolide-resistant and multiresistant organisms.

[Pulmonary diffusion of antibiotics. Critical analysis of the literature]

OBJECTIVES

Collect exhaustive data from the literature concerning the diffusion of antibiotics into lung tissue and calculate their inhibitory quotient towards the germs most frequently encountered in pulmonary infections.

DATA SOURCES

Review of the literature. Data collected from the Medline database with the key words: lung, diffusion, disposition, antibiotics. Inhibitory quotients calculated from these data.

RESULTS

The results were relatively similar for the different types of samples, though some differences existed between the studies. These differences were caused in particular by methodological difficulties for the tissue dosage of antibiotics.

CONCLUSION

Further standardized studies, measuring in particular the antibiotic concentration in the epithelial lining fluid and in the alveolar macrophages, are necessary to obtain more reliable results in terms of inhibitory quotients. Only clinical studies, perhaps with the help of these data, could establish the real efficiency of antibiotics in lung infections.

Pharmacokinetic population study to describe cefepime lung concentrations

Pharmacokinetic parameters of cefepime in 2 g plasma and lung tissue bid over 3 days to achieve the steady-state was studied in 16 patients (15 male, one female) subjected to lung surgery for bronchial epithelioma. The aims of this study were firstly to quantify cefepime lung diffusion with cefepime lung concentrations in comparison with cefepime serum concentrations, and secondly to estimate population pharmacokinetic parameters of cefepime in lung tissue using NONMEM. The mean characteristics of patients were: age, 60 years (range, 51-69 years), weight, 73 kg (range, 62-87 kg) and creatinine clearance, 77 ml/min (range, 62-92 ml/min). Both serum sample (two per patient) and lung sample (one per patient) cefepime concentrations were analysed by HPLC with UV detection. Five groups were made according to the time of sampling after the last cefepime intravenous infusion at the fifth infusion: 0.5 h (n=2), 2 h (n=5), 4 h (n=3), 8 h (n=3) and 12 h (n=3). The cefepime concentration ratio between lung and serum was calculated for each group and statistical analysis show no significant difference between groups. The mean concentration ratio between lung and serum was 101% (range, 70-130%). To explain this observation a two-compartment pharmacokinetic model with a population approach was used to describe pharmacokinetic parameters of cefepime both in lung and in serum. Serum was assimilated at the central compartment and lung was the peripheral compartment. NONMEM was used to estimate the mean and the variance of the pharmacokinetic parameters. Central volume of distribution (V(d)), steady-state volume of distribution (V(ss)), central clearance (CL) and transfer constants (K(cp)) from serum to lung and (K(pc)) from lung to serum were estimated. Central elimination half-life t(1/2Kbeta)was extrapolated from elimination constant beta. Results were: V(d)= 15.62 +/- 2.56 l, V(ss)= 17.58 +/- 2.58 l, CL = 3.65 +/- 1.25 l/h, beta = 0.234 h(-1), t(1/2beta)= 2.96 hours, K(cp)= 12.25 +/- 8.56 h(-1)and K(pc)= 0.242 +/- 0.085 h(-1). The results show that cefepime diffusion in lung occurs quickly without lagtime and in similar concentrations to that in serum.

Genitourinary chlamydial infection: a reappraisal and hypothesis

Our understanding of genitourinary chlamydial infection and disease remains limited. That natural defences and/or apparently adequate treatments leave some patients with latent disease is suspected. There is, however, no consensus as to its nature. Furthermore, many patients, most obviously males, presenting with similar or identical symptoms and signs remain unexplained in microbiological terms; this in spite of many years of dedicated research endeavour. The recent trend towards an impasse has coincided with a growing acquaintance with the immunobiology and immunopathology of chlamydial infections. The time would seem to have arrived for a reappraisal of available clinical and laboratory observations. A hypothesis with research suggestions is presented for discussion.

Concentration of enrofloxacin and its active metabolite in alveolar macrophages and pulmonary epithelial lining fluid of dogs

The purpose of this study was to determine the concentration of enrofloxacin and its active metabolite, ciprofloxacin, in alveolar macrophages (AM) and epithelial lining fluid (ELF) of the lungs in comparison to plasma concentrations in healthy dogs. Eleven dogs were given a single oral dose (5 mg/kg) of enrofloxacin. Four hours later, plasma and bronchoalveolar lavage (BAL) fluid were collected. Cells were separated from the BAL fluid and lysed for determination of drug concentrations within AM. Supernatant was used to determine concentrations of drugs in ELF. Drug assays were performed by high-performance liquid chromatography. The concentration of enrofloxacin (mean +/- SD) was 0.33 +/- 0.14 microgram/mL in plasma, 3.34 +/- 2.4 micrograms/mL in AM and 4.79 +/- 5.0 micrograms/mL in ELF. The concentration of ciprofloxacin was 0.42 +/- 0.26 microgram/mL in plasma, 1.15 +/- 1.03 micrograms/mL in AM and 0.26 +/- 0.26 microgram/mL in ELF. Mean concentrations of both drugs in AM were greater than in plasma (AM to plasma ratio, 10.3 for enrofloxacin and 4.7 for ciprofloxacin). Mean concentrations of enrofloxacin, but not ciprofloxacin, in ELF were greater than in plasma (ELF to plasma ratio, 13.5 for enrofloxacin and 0.52 for ciprofloxacin). Enrofloxacin concentrations in AM and ELF largely exceeded the MICs of the major bacterial pathogens and surpassed by about two times the breakpoint MIC of that drug, and ciprofloxacin concentrations in AM surpassed the MIC of many susceptible organisms. These results suggest that sufficient antimicrobial activity is present in AM and ELF of dogs following oral administration of enrofloxacin to be effective in the treatment of lower respiratory tract infections involving susceptible organisms.

Effect of macrolide antibiotics on macrophage functions

Macrolide antibiotics have a variety of actions other than antimicrobial activities. Recently, it has been suggested that macrolide antibiotics act as immunomodulators. In this study, we evaluated the effects of macrolide antibiotics on macrophage functions. For the macrophage, we used the mouse macrophage cell line J774.1. The following effects of macrolide antibiotics on macrophage functions were evaluated: the effect of macrolide antibiotics on macrophage growth; the phagocytosis of beads; cytocidal activity against Candida albicans; and chemotaxis to lipopolysaccharide (LPS). Macrolide antibiotics except for azithromycin significantly stimulated the growth of the macrophage. In addition, pretreatment with macrolide antibiotics except for roxithromycin significantly stimulated the macrophage phagocytosis of beads, macrophage chemotaxis to LPS, and macrophage cytocidal activity against Candida albicans. These results suggest that macrolide antibiotics stimulate macrophage functions.

Pharmacokinetics of antimicrobial agents in the respiratory tract

The ability of antibiotics to penetrate into the respiratory tract has been investigated at several sites, namely, sputum and bronchial secretions, tissue homogenates, pleural fluid and, more recently, epithelial lining fluid and alveolar macrophages. The major reason for such investigations is that these data may be helpful to a more thorough understanding of drug distribution in the lung tissue and fluids and to a more accurate prediction of clinical outcome. However, the study of drug concentration at each of these sites presents problems in terms of methodology and data interpretation. The advantages and disadvantages of each of these methods are considered, and the data on penetration of betalactams, aminoglycosides, macrolides, fluoroquinolones and other antimicrobial agents (including antifungal and antiprotozoan drugs) are reviewed.

Comparative bronchoalveolar concentrations of ciprofloxacin and lomefloxacin following oral administration

In a comparative study, the concentrations of two fluoroquinolone antimicrobials, ciprofloxacin and lomefloxacin, were measured in serum, bronchial mucosal biopsies, epithelial lining fluid (ELF) and alveolar macrophages (AM). Thirty-four subjects received either ciprofloxacin 250 mg b.d. (17 subjects) or lomefloxacin 400 mg o.d. for 4 days prior to sampling by bronchoscopic bronchial biopsy and bronchoalveolar lavage. Both ciprofloxacin and lomefloxacin showed favourable accumulation in the sites of infection with bronchial biopsy concentrations of 1.6 and 1.7 times those of serum respectively; ELF concentrations of 2.1 and 1.9 times serum; and AM concentrations of 11.8 and 20.1 times serum respectively. The MIC90 for most of the common chest pathogens was reliably exceeded by both agents except for that of Streptococcus pneumoniae.

Analysis of vancomycin entry into pulmonary lining fluid by bronchoalveolar lavage in critically ill patients

Vancomycin penetration into the fluid lining the epithelial surface of the lower respiratory tract was studied by performing fiberoptic bronchoscopy with bronchoalveolar lavage on 14 critically ill, ventilated patients who had received the drug for at least 5 days. The apparent volume of epithelial lining fluid (ELF) recovered by bronchoalveolar lavage was determined by using urea as an endogenous marker. Vancomycin levels in ELF ranged from 0.4 to 8.1 micrograms/ml (mean, 4.5 micrograms/ml), while the mean simultaneous level of the drug in plasma was 24 micrograms/ml (range, 9 to 37.4 micrograms/ml). There was a significant relationship (r = 0.64, P < 0.02) between vancomycin levels in plasma and those in ELF, with a correlation whose slope (0.15) indicated that the blood-to-ELF ratio of drug penetration was 6:1. Using the albumin concentration in ELF as a marker of lung inflammation, we found that vancomycin penetration was higher in patients with ELF albumin values of > or = 3.4 mg/ml than in patients with normal values (< 3.4 mg/ml) (P < 0.02). These results suggest that the vancomycin distribution includes the ELF of the lower respiratory tract at a concentration that is dependent upon the levels in blood and the alveolar capillary membrane protein permeability. These concentrations were well above the MICs for most staphylococci and enterococci.

Penetration of cefpodoxime proxetil in lung parenchyma and epithelial lining fluid of noninfected patients

The pulmonary disposition of cefpodoxime was studied in 12 patients with pulmonary opacities after a single oral dose of 260 mg of cefpodoxime-proxetil, which is equivalent to 200 mg of cefpodoxime. Blood and lung tissue samples were collected during surgery, and bronchoalveolar lavage was carried out 3 h (group A) or 6 h (group B) after drug administration. Urea was used as an endogenous marker for measurement of the volume of epithelial lining fluid (ELF). Concentrations were measured by using a microbiological assay. The mean concentrations of cefpodoxime in plasma, ELF, and lung tissue were, respectively, 1.85 +/- 0.82 mg/liter, 0.22 +/- 0.13 mg/liter, and 0.89 +/- 0.80 mg/kg of body weight in group A and 1.40 +/- 1.25 mg/liter, 0.12 +/- 0.14 mg/liter, and 0.84 +/- 0.61 mg/kg in group B. Concentrations in lung parenchyma 6 h after dosing were at least equal to or above the MICs for 90% of the strains of most organisms commonly found in respiratory tract infections, whereas data for ELF suggest levels of drug insufficient to inhibit bacteria.

Pulmonary disposition of antimicrobial agents: methodological considerations

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Clinical evaluation of roxithromycin 300 mg once daily as an alternative to 150 mg twice daily

A multicenter, double-blind, randomized, two-arm study was conducted to compare two dosage regimens of roxithromycin--150 mg b.i.d. and 300 mg once daily--in 1588 patients with infectious disease, 1573 of whom were evaluable for safety and 1391 for efficacy. There were no significant differences in demographic or disease characteristics at presentation. Treatment duration averaged 10 days in both groups. Clinical response rates (% satisfactory response) were similar in both arms (b.i.d. versus once daily, respectively): upper respiratory tract, 95.3 and 95.0; lower respiratory tract, 93.1 and 93.6; and skin and soft tissue, 93.1 and 93.0. Bacteriologic response was also similar. The overall incidences of adverse events were 8.5% for daily dosing and 7.2% for b.i.d. dosing, but there was a slightly greater frequency of gastrointestinal events (p less than 0.03) was observed with the once-daily regimen. Thus roxithromycin 300 mg once daily can be recommended as an effective and well-tolerated alternative to the conventional b.i.d. regimen.

Roxithromycin versus amoxicillin-clavulanic acid in the treatment of respiratory tract infections

A multicenter, double-blind, double-dummy trial was conducted in 96 general practice patients with upper and lower respiratory tract infection to compare the efficacy and tolerance of roxithromycin (150 mg b.i.d.) and amoxicillin-clavulanic acid (500 mg/125 mg t.i.d.). Good clinical response was obtained in 96% and 95% of cases, respectively, but only 4% of patients receiving roxithromycin volunteered adverse events possibly or probably related to their test treatment, as opposed to 17% of those receiving amoxicillin-clavulanic acid. The results indicate that both drugs are equally effective in the treatment of respiratory tract infection, but that roxithromycin is better tolerated.

Penetration of netilmicin in the lower respiratory tract after once-daily dosing

A major criticism of the use of aminoglycosides for the treatment of pneumonia is the poor penetration in infected airways. Once-daily dosing of aminoglycosides results in higher peak plasma concentrations without increasing toxic reactions and with optimization of pharmacodynamic properties. To predict intrapulmonary antimicrobial activity after once-daily dosing of aminoglycosides, it is necessary to determine the respective bronchial and alveolar disposition. We prospectively conducted a pharmacokinetic study of netilmicin following the first intravenous administration of a once-daily dosing schedule in 20 ventilated patients with pneumonia. A bronchoscopic sampling of bronchial secretions and a subsegmental bronchoalveolar lavage (BAL) were performed 60, 90, 120, and 180 min (five patients at each time point) on the first treatment day after intravenous administration over 30 min of 450 mg of netilmicin. The netilmicin concentrations in the alveolar lining fluid (ALF) were calculated using urea as an endogenous marker of dilution. In bronchial secretions, a peak concentration of 2.00 (SEM: 0.26) mg/L or 6 percent of the 30-min plasma concentration was reached at 120 min. In ALF, much higher levels were found. At 120 min, a peak ALF concentration of 14.7 (SEM: 2.22) mg/L or 41 percent of the 30-min plasma concentration was reached. Spearman's rank correlation testing failed to show a correlation between bronchial and ALF concentrations. Higher plasma concentrations of netilmicin after once-daily dosing give rise to ALF concentrations exceeding the minimum inhibitory concentration of susceptible respiratory pathogens involved in nosocomial pneumonia, while bronchial concentrations remain low. Aminoglycoside concentrations in bronchial secretions cannot be used to predict alveolar concentrations. Low diffusibility can no longer be considered as a disadvantage of aminoglycosides for treating pneumonias.

Cefpodoxime proxetil in upper respiratory tract infections

Cefpodoxime proxetil is a new third generation oral cephalosporin, which shows potent antibacterial activity against both Gram-positive and Gram-negative bacteria, and high stability in the presence of beta-lactamases. Low concentrations of cefpodoxime inhibit most respiratory pathogens, including Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella (Branhamella) catarrhalis. Cefpodoxime reaches concentrations of 0.24 +/- 0.06 mg/kg in tonsils, 0.89 +/- 0.80 mg/kg in lung parenchyma, and 0.91 +/- 0.01 mg/kg in bronchial mucosa; these values exceed by far the minimum inhibitory concentrations (MICs) of cefpodoxime for respiratory pathogens. Preliminary clinical studies were carried out in 181 patients with upper respiratory tract infections: the results indicated an overall clinical response in 88.4% of patients; in 30% the clinical efficacy was excellent and in 58.5% it was good. Further studies showed clinical cure in 90.3% of patients with pharyngotonsillitis, and clinical efficacy (cure plus improvement) in 95% of those with acute sinusitis. Moreover, bacterial eradication was obtained in 78 to 96.7% of cases, most of which involved H. influenzae, streptococci, or M. catarrhalis. Cefpodoxime appears to be an effective new antibacterial that can be recommended as a drug of first choice in the treatment of most upper respiratory tract infections.

Concentrations of temafloxacin in serum and bronchial mucosa

The bronchial mucosal concentrations of temafloxacin hydrochloride were determined in specimens obtained at fibreoptic bronchoscopy and compared with simultaneous serum concentrations. The 18 patients studied were given an oral dose of 400 mg b.i.d for three days to achieve steady state levels. The mean serum concentration was 6.9 mg/l (SD 2.5 mg/l) and the mean bronchial mucosal concentration 12.2 mg/kg (SD 4 mg/kg). The mucosal levels exceeded those required to inhibit most of the common respiratory pathogens, including Streptococcus pneumoniae and Pseudomonas aeruginosa. These data support the use of temafloxacin for therapy of bronchial infections.

Concentrations of oral lomefloxacin in serum and bronchial mucosa

The bronchial mucosal concentrations of lomefloxacin were determined for specimens obtained by fiber-optic bronchoscopy and compared with simultaneous concentrations in serum. The 23 patients studied were given an oral dose of 400 mg once daily for 4 days to achieve steady-state levels. The median concentration in serum was 2.5 micrograms/ml (range, 1.0 to 5 micrograms/ml), and the median bronchial mucosal concentration was 5.0 micrograms/g (range, 0.7 to 18.6 micrograms/g). The median percent penetration was 177% (range, 69 to 541%). The concentrations in serum and mucosa exceeded the MIC for 90% of strains of organisms causing bronchial infections but not sufficiently to recommend lomefloxacin for the routine treatment of pneumococcal infections.

Influence of cytostatic treatment on the efficacy of erythromycin and roxithromycin in a staphylococcal infection in mice

Mice made monocytopenic with etoposide or both granulocytopenic and monocytopenic with cyclophosphamide were infected in a thigh muscle with 3 x 10(6) CFU of Staphylococcus aureus; 1 h later erythromycin or roxithromycin was administered, and 4 h after that the number of CFU per thigh was determined. In vitro as well as in vivo, the maximal effect of both antibiotics was only bacteriostatic. Monocytopenia did not diminish the efficacy of either erythromycin or roxithromycin in vivo, whereas the combination of granulocytopenia and monocytopenia markedly decreased the efficacy of both drugs: a 4-fold dose increase was necessary to obtain the same final number of CFU at the site of infection as in the controls. It is concluded that granulocytes contributed substantially to antibiotic efficacy against S. aureus in this short-term infection model.

Roxithromycin. A review of its antibacterial activity, pharmacokinetic properties and clinical efficacy

Roxithromycin is an acid-stable orally administered antibacterial macrolide structurally related to erythromycin. It has an in vitro antibacterial profile similar to that of erythromycin, with activity against Staphylococcus aureus, S. epidermidis, Streptococcus pneumoniae, S. pyogenes, Branhamella catarrhalis, Mycoplasma pneumoniae, Legionella pneumophila, Chlamydia trachomatis, Gardnerella vaginalis, Haemophilus ducreyi, some anaerobes and other less common pathogens. Roxithromycin has a pharmacokinetic profile that is characterised by excellent enteral absorption achieving high concentrations in most tissues and body fluids. The results of clinical studies with roxithromycin have confirmed the potential for its use in a variety of infections, which was suggested by its antibacterial activity in vitro and pharmacokinetic profile. Clinical efficacy has been confirmed in the treatment of respiratory tract infections, including community-acquired and atypical pneumonias, ear, nose and throat infections, genitourinary tract infections, and skin and soft tissue infections. In a relatively small number of patients roxithromycin has generally been shown to be as effective as erythromycin and other appropriate antibacterial drugs in some of the above indications. Roxithromycin is well tolerated and has less potential than erythromycin to produce clinically significant drug interactions. Thus, roxithromycin is an orally active drug which should prove a useful alternative when selecting antibacterial therapy for indications where macrolides are appropriate.