Pulmonary Epithelial Lining Fluid Research Articles

Biopharmaceutical Characterization of Nebulized Antimicrobial Agents in Rats: 6. Aminoglycosides.

Amikacin and gentamicin pharmacokinetic behaviors after nebulization were determined by comparing plasma and pulmonary epithelial lining fluid (ELF) concentrations in rats after intratracheal and intravenous administrations. ELF areas under concentration-time curve were 874 and 162 times higher after nebulization than after intravenous administration for amikacin and gentamicin, respectively. Even if both molecules appear to be good candidates for nebulization, these results demonstrate a much higher targeting advantage of nebulization for amikacin than for gentamicin.

A strategy for designing voriconazole dosage regimens to prevent invasive pulmonary aspergillosis based on a cellular pharmacokinetics/pharmacodynamics model

BackgroundInvasive pulmonary aspergillosis (IPA) is a life-threatening disease in immunosuppressed patients. Voriconazole is commonly used to prevent and treat IPA in the clinic, but the optimal prophylactic antifungal regimen is unknown. The objective of this study was to clarify the mechanism underlying how voriconazole prevents IPA based on a target cellular pharmacokinetics/pharmacodynamics model, with the aim of identifying a way to design an optimal prophylactic antifungal regimen.MethodsA nystatin assay was used to establish a target-cells model for A. fumigatus infection. An inhibitory effect sigmoid Emax model was developed to explore the cellular PK/PD breakpoint, and Monte Carlo simulation was used to design the prophylactic antifungal regimen.ResultsThe intracellular activity of voriconazole in the target cells varied with its concentration, with the minimum inhibitory concentration (MIC) being an important determinant. For A. fumigatus strains AF293 and AF26, voriconazole decreased the intracellular inoculum by 0.79 and 0.84 lg cfu, respectively. The inhibitory effect sigmoid Emax model showed that 84.01% of the intracellular inoculum was suppressed by voriconazole within 24 h, and that a PK/PD value of 35.53 for the extracellular voriconazole concentration divided by MIC was associated with a 50% suppression of intracellular A. fumigatus. The Monte Carlo simulation results showed that the oral administration of at least 200 mg of voriconazole twice daily was yielded estimated the cumulative fraction of response value of 91.48%. Concentration of voriconazole in the pulmonary epithelial lining fluid and the plasma of > 17.77 and > 1.55 mg/L, respectively, would ensure the PK/PD > 35.53 for voriconazole against most isolates of A. fumigatus and may will be benefit to prevent IPA in clinical applications.ConclusionsThis study used a target cellular pharmacokinetics/pharmacodynamics model to reveal a potential mechanism underlying how voriconazole prevents IPA and has provided a method for designing voriconazole prophylactic antifungal regimen in immunosuppressed patients.

Pharmacokinetics of florfenicol in turkey plasma, lung tissue, and pulmonary epithelial lining fluid after single oral bolus or continuous administration in the drinking water

Florfenicol (FF) is registered for treatment of bovine and swine respiratory diseases. Although, turkeys often suffer from bacterial respiratory tract infections, there is no registered formulation based on FF for poultry available in Europe. The aim of this study was to evaluate the pharmacokinetic behavior of FF in turkeys in plasma, lung tissue, and pulmonary epithelial lining fluid (PELF).The concentration and pharmacokinetic characteristics of FF in plasma, lung tissue, and PELF in turkeys were determined, either after a single oral bolus (30mg/kg body weight, BW) or during and after continuous drinking water medication (30mg/kg BW/d for 5 d). Plasma, lung tissue, and PELF samples were collected at different intervals after administration, and FF was quantified by liquid chromatography-tandem mass spectrometry. After single bolus administration, FF was rapidly absorbed in plasma (the time to maximum concentration, tmax, was 1.02h) and distributed to the respiratory tract (mean tmax = 1.00h). The mean t1/2el in plasma and lung tissue was similar, around 6h, whereas it was slightly higher in PELF, namely, 8.7hours. After oral bolus dosing, the mean maximum concentration in plasma was twice as high as in the lung tissue, 4.26μg/mL and 2.64μg/g, respectively, while in PELF it was much lower, 0.39μg/mL. During continuous drinking water medication, lung FF concentrations were slightly higher than plasma concentrations, with lung/plasma ratios of 2.01 and 1.27 after 24h and 72h, respectively. FF was not detected in PELF during continuous drinking water medication.

Salmeterol undergoes enantioselective bronchopulmonary distribution with receptor localisation a likely determinant of duration of action

BackgroundSalmeterol (a long acting beta2-agonist) is a chiral molecule. (RR)-salmeterol is responsible for pharmacological effect, but basic knowledge of enantioselective pulmonary pharmacodynamics and pharmacokinetics of salmeterol remains unknown. There are safety concerns with (S)-enantiomers of beta2-agonists, with suggestions that these enantiomers may increase bronchial hyperresponsivneness in asthma patients. MethodologyHorses (n = 12) received racemic (rac-) salmeterol 250 μg via inhalation. Enantioselective UPLC–MS/MS was used to determine (R)- and (S)-salmeterol concentrations in pulmonary epithelial lining fluid (PELF) sampled 2, 5, 10 and 15 min after administration, in central lung (endoscopic bronchial biopsy) and peripheral lung (percutaneous pulmonary biopsy) tissues (at 20 and 25 min respectively), and in plasma samples. ResultsPhysiologically relevant tissue concentrations were found for both enantiomers, with median levels greater in central than peripheral lung (equivalent to 32 and 5 mM (R)-salmeterol for central and peripheral lung respectively). Levels in PELF decreased around 50% over 15 min and enantioselective distribution was observed in the central lung with levels of (R)-salmeterol around 30% higher than (S)-salmeterol. ConclusionSalmeterol distribution is enantioselective in the central lung. This suggests duration of action is more likely associated with specific B2ADR localisation effects rather than non-specific physiochemical factors which would not be enantioselective.

Exhaled breath condensate as an alternative sample for drug monitoring.

Exhaled breath condensate as an alternative sample for drug monitoring.

Bronchopulmonary pharmacokinetics of (R)-salbutamol and (S)-salbutamol enantiomers in pulmonary epithelial lining fluid and lung tissue of horses.

Salbutamol is usually administered as a racemic mixture but little is known about the enantioselectivity of salbutamol pharmacokinetics in the lung. This study was designed to investigate enantiomer concentrations in lung tissue after inhaled dosing. Horses (n=12) received racemic salbutamol 1000 μg via inhalation. Enantioselective ultra performance liquid chromatography-tandem mass spectrometry was used to determine salbutamol concentrations in pulmonary epithelial lining fluid (PELF) sampled 2, 5, 10 and 15min after administration, in central lung (endoscopic bronchial biopsy) and peripheral lung (percutaneous pulmonary biopsy) tissues (at 20 and 25min respectively), and in plasma samples. Mean±95% confidence interval (CI) yield of PELF was 57±10mg. Initial mean±95%CI (R)- and (S)-salbutamol PELF concentrations were 389±189ngg-1 and 378±177ngg-1 respectively, and both reduced approximately 50% by 15min. Mean±95%CI central lung levels of drug were higher than peripheral lung tissue for both (R)-salbutamol (875±945 vs. 49.5±12ngg-1 ) and (S)-salbutamol (877±955 vs. 50.9±12ngg-1 ) respectively. There was no evidence of enantioselectivity in PELF or central lung but minor (~2%) enantioselectivity was observed in the peripheral lung. Enantioselectivity was clearly evident in plasma with (S):(R) ratio of 1.25 and 1.14 for both area under the concentration-time curve (0-25min) and Cmax respectively. PELF sampling in horses offers sufficient yield allowing direct detection of drug and, combined with tissue sampling, is a valuable model to investigate bronchopulmonary pharmacokinetics. Salbutamol did not demonstrate enantioselectivity in PELF or central lung tissue uptake following acute dosing, however, enantioselective plasma concentrations were demonstrated, with minor enantioselectivity in the peripheral lung.

4-6 気管支鏡下マイクロサンプリング法による肺上皮被覆液の解析 : 各種病態への応用( 第28回日本呼吸器内視鏡学会総会)

4-6 気管支鏡下マイクロサンプリング法による肺上皮被覆液の解析 : 各種病態への応用( 第28回日本呼吸器内視鏡学会総会)

Comparative pharmacokinetics of minocycline in foals and adult horses.

The objective of this study was to compare the pharmacokinetics of minocycline in foals vs. adult horses. Minocycline was administered to six healthy 6-to 9-week-old foals and six adult horses at a dose of 4mg/kg intragastrically (IG) and 2mg/kg intravenously (i.v.) in a cross-over design. Five additional oral doses were administered at 12-h intervals in foals. A microbiologic assay was used to measure minocycline concentration in plasma, urine, synovial fluid, and cerebrospinal fluid (CSF). Liquid chromatography-tandem mass spectrometry was used to measure minocycline concentrations in pulmonary epithelial lining fluid (PELF) and bronchoalveolar (BAL) cells. After i.v. administration to foals, minocycline had a mean (±SD) elimination half-life of 8.5±2.1h, a systemic clearance of 113.3±26.1mL/h/kg, and an apparent volume of distribution of 1.24±0.19L/kg. Pharmacokinetic variables determined after i.v. administration to adult horses were not significantly different from those determined in foals. Bioavailability was significantly higher in foals (57.8±19.3%) than in adult horses (32.0±18.0%). Minocycline concentrations in PELF were higher than in other body fluids. Oral minocycline dosed at 4mg/kg every 12h might be adequate for the treatment of susceptible bacterial infections in foals.

Pharmacokinetics and distribution in interstitial and pulmonary epithelial lining fluid of danofloxacin in ruminant and preruminant calves.

The objective of this study was to compare active drug concentrations in the plasma vs. different effector compartments including interstitial fluid (ISF) and pulmonary epithelial lining fluid (PELF) of healthy preruminating (3-week-old) and ruminating (6-month-old) calves. Eight calves in each age group were given a single subcutaneous (s.c.) dose (8mg/kg) of danofloxacin. Plasma, ISF, and bronchoalveolar lavage (BAL) fluid were collected over 96h and analyzed by high-pressure liquid chromatography. PELF concentrations were calculated by a urea dilution assay of the BAL fluids. Plasma protein binding was measured using a microcentrifugation system. For most preruminant and ruminant calves, the concentration-time profile of the central compartment was best described by a two-compartment open body model. For some calves, a third compartment was also observed. The time to maximum concentration in the plasma was longer in preruminating calves (3.1h) vs. ruminating calves (1.4h). Clearance (CL/F) was 385.15 and 535.11mL/h/kg in preruminant and ruminant calves, respectively. Ruminant calves maintained higher ISF/plasma concentration ratios throughout the study period compared to that observed in preruminant calves. Potential reasons for age-related differences in plasma concentration-time profiles and partitioning of the drug to lungs and ISF as a function of age are explored.

The Epidemiologic and Pharmacodynamic Cutoff Values of Tilmicosin against Haemophilus parasuis.

The aim of this study was to establish antimicrobial susceptibility breakpoints for tilmicosin against Haemophilus parasuis, which is an important pathogen of respiratory tract infections. The minimum inhibitory concentrations (MICs) of 103 H. parasuis isolates were determined by the agar dilution method. The wild type (WT) distribution and epidemiologic cutoff value (ECV) were evaluated by statistical analysis. The new bronchoaveolar lavage was used to establish intrapulmonary pharmacokinetic (PK) model in swine. The pharmacokinetic (PK) parameters of tilmicosin, both in pulmonary epithelial lining fluid (PELF) and in plasma, were determined using high performance liquid chromatography method and WinNonlin software. The pharmacodynamic cutoff (COPD) was calculated using Monte Carlo simulation. Our results showed that 100% of WT isolates were covered when the ECV was set at 16 μg/mL. The tilmicosin had concentration-dependent activity against H. parasuis. The PK data indicated that tilmicosin concentrations in PELF was rapidly increased to high levels at 4 h and kept stable until 48 h after drug administration, while the tilmicosin concentration in plasma reached maximum levels at 4 h and continued to decrease during 4–72 h. Using Monte Carlo simulation, COPD was defined as 1 μg/mL. Conclusively, the ECV and COPD of tilmicosin against H. parasuis were established for the first time based on the MIC distribution and PK-PD analysis in the target tissue, respectively. These values are of great importance for detection of tilmicosin-resistant H. parasuis and for effective treatment of clinical intrapulmonary infection caused by H. parasuis.

Biopharmaceutical Characterization of Nebulized Antimicrobial Agents in Rats. 4. Aztreonam.

The aim of this study was to determine aztreonam (ATM) membrane permeability using Calu-3 cells and its plasma and pulmonary epithelial lining fluid (ELF) pharmacokinetics in rats after intratracheal nebulization and intravenous administration (15 mg · kg(-1)). ATM exhibits low Calu-3 permeability (0.07 ± 0.02 × 10(-6) cm · s(-1)), and a high area under the ELF/unbound plasma concentration time curve between 0 and infinity (AUCELF/AUCu,plasma) ratio of 1,069 was observed after nebulization in rats. These results confirm that ATM is a low-permeability molecule and a good candidate for nebulization.

Pulmonary vasculature directed adenovirus increases epithelial lining fluid alpha-1 antitrypsin levels.

Gene therapy for inherited serum deficiency disorders has previously been limited by the balance between obtaining adequate expression and causing hepatic toxicity. Our group has previously described modifications of a replication deficient human adenovirus serotype 5 that increase pulmonary vasculature transgene expression. In the present study, we use a modified pulmonary targeted adenovirus to express human alpha-1 antitrypsin (A1AT) in C57BL/6 J mice. Using the targeted adenovirus, we were able to achieve similar increases in serum A1AT levels with less liver viral uptake. We also increased pulmonary epithelial lining fluid A1AT levels by more than an order of magnitude compared to that of untargeted adenovirus expressing A1AT in a mouse model. These gains are achieved along with evidence of decreased systemic inflammation and no evidence for increased inflammation within the vector-targeted end organ. In addition to comprising a step towards clinically viable gene therapy for A1AT, maximization of protein production at the site of action represents a significant technical advancement in the field of systemically delivered pulmonary targeted gene therapy. It also provides an alternative to the previous limitations of hepatic viral transduction and associated toxicities.

Penetration of antimicrobials to pulmonary epithelial lining fluid and muscle and impact of drug physicochemical properties determined by microdialysis

IntroductionThe objectives of this study were to characterize antimicrobial drug penetration into the pulmonary epithelial lining fluid (PELF) and extracellular fluid (ECF) of muscle in relation to physicochemical properties of the drugs (molecular mass, Log D, polar surface area and charge), using intrabronchial microdialysis. The series of drugs tested include gentamicin, sulfadiazine, cefquinome, minocycline and colistin. MethodsDrug concentrations were measured during 2h of steady state plasma drug concentrations at therapeutic levels in anesthetized pigs. Microdialysis probes were positioned 2 to 4cm distal to the tracheal bifurcature and in M. gluteobiceps and were calibrated by retrodialysis by drug. ResultsMean AUCPELF/PLASMA(fu) and mean AUCMUSCLE/PLASMA(fu) ratios were respectively for gentamicin (0.8, 0.7), sulfadiazine (1.1, 0.7), cefquinome (1.3, 1.5) minocycline (1.6, 0.7) and colistin (0.26, 0.12). The penetration of drugs into PELF (r2=0.55–0.77, p=0.0004–0.0089) and ECF of muscle (r2=0.39–0.53, p=0.0108–0.0397) was positively correlated to Log D, whereas molecular mass, polar surface area and charge were negatively correlated to drug penetration. Sulfadiazine, gentamicin, cefquinome and colistin had similar penetration ratios into PELF and ECF of muscle, ranging from 0.12 to 1.50. DiscussionIn conclusion, drug penetration into PELF and ECF of muscle is correlated to mass, lipophilicity, polarity and charge of the drugs. Drug partition into ECF of muscle and PELF are similar for the passively transported drugs gentamicin, sulfadiazine, cefquinome and colistin, whereas minocycline appears to be actively transported into PELF.

Pharmacokinetics and pharmacodynamics of gamithromycin in pulmonary epithelial lining fluid in naturally occurring bovine respiratory disease in multisource commingled feedlot cattle

The objectives of this study were to determine (i) whether an association exists between individual pharmacokinetic parameters and treatment outcome when feeder cattle were diagnosed with bovine respiratory disease (BRD) and treated with gamithromycin (Zactran(®) ) at the label dose and (ii) whether there was a stronger association between treatment outcome and gamithromycin concentration in plasma or in the pulmonary epithelial lining fluid (PELF) effect compartment. The study design was a prospective, blinded, randomized clinical trial utilizing three groups of 60 (362-592lb) steers/bulls randomly allocated within origin to sham injection or gamithromycin mass medication. Cattle were evaluated daily for signs of BRD by a veterinarian blinded to treatment. Animals meeting the BRD case definition were enrolled and allocated to a sample collection scheme consisting of samples for bacterial isolation (bronchoalveolar lavage fluid and nasopharyngeal swabs) and gamithromycin concentration determination (PELF and plasma). Gamithromycin susceptibility of M.haemolytica (n=287) and P.multocida (n=257) were determined using broth microdilution with frozen panels containing gamithromycin at concentrations from 0.03 to 16μg/mL. A two-compartment plasma pharmacokinetic model with an additional compartment for gamithromycin in PELF was developed using rich data sets from published and unpublished studies. The sparse data from our study were then fit to this model using nonlinear mixed effects modeling to estimate individual parameter values. The resulting parameter estimates were used to simulate full time-concentration profiles for each animal in this study. These profiles were analyzed using noncompartmental methods so that PK/PD indices (AUC24 /MIC, AUC∞ /MIC, CMAX /MIC) could be calculated for plasma and PELF (also T>MIC) for each individual. The calculated PK/PD indices were indicative that for both M.haemolytica and P.multocida a higher drug exposure in terms of concentration, and duration of exposure relative to the MIC of the target pathogen, was favorable to a successful case outcome. Asignificant association was found between treatment success and PELF AUC0-24 /MIC for P.multocida. The calves in this study demonstrated an increased clearance and volume of distribution in plasma as compared to the healthy calves in two previously published reports. Ultimately, the findings from this study indicate that higher PK/PD indices were predictive of positive treatment outcomes.

Radical Formation in the Gas-Phase Ozonolysis of Deprotonated Cysteine

Although the deleterious effects of ozone on the human respiratory system are well-known, many of the precise chemical mechanisms that both cause damage and afford protection in the pulmonary epithelial lining fluid are poorly understood. As a key first step to elucidating the intrinsic reactivity of ozone with proteins, its reactions with deprotonated cysteine [Cys-H]- are examined in the gas phase. Reaction proceeds at near the collision limit to give a rich set of products including 1) sequential oxygen atom abstraction reactions to yield cysteine sulfenate, sulfinate and sulfonate anions, and significantly 2) sulfenate radical anions formed by ejection of a hydroperoxy radical. The free-radical pathway occurs only when both thiol and carboxylate moieties are available, implicating electron-transfer as a key step in this reaction. This novel and facile reaction is also observed in small cys-containing peptides indicating a possible role for this chemistry in protein ozonolysis. Gas-phase reactions: Deprotonated cysteine reacted with ozone to give a rich set of products including sequential oxygen atom abstraction reactions to yield cysteine sulfenate, sulfonate, and sulfonate anions, and significantly sulfenate radical anions formed by ejection of a hydroperoxy radical (see picture). The free-radical pathway occurred only when both thiol and carboxylate moieties were available.

Radical Formation in the Gas-Phase Ozonolysis of Deprotonated Cysteine.

Although the deleterious effects of ozone on the human respiratory system are well-known, many of the precise chemical mechanisms that both cause damage and afford protection in the pulmonary epithelial lining fluid are poorly understood. As a key first step to elucidating the intrinsic reactivity of ozone with proteins, its reactions with deprotonated cysteine [Cys-H](-) are examined in the gas phase. Reaction proceeds at near the collision limit to give a rich set of products including 1) sequential oxygen atom abstraction reactions to yield cysteine sulfenate, sulfinate and sulfonate anions, and significantly 2) sulfenate radical anions formed by ejection of a hydroperoxy radical. The free-radical pathway occurs only when both thiol and carboxylate moieties are available, implicating electron-transfer as a key step in this reaction. This novel and facile reaction is also observed in small cys-containing peptides indicating a possible role for this chemistry in protein ozonolysis.

Pharmacokinetic and pharmacodynamic properties of gamithromycin in turkey poults with respect to Ornithobacterium rhinotracheale

The macrolide gamithromycin (GAM) has the ability to accumulate in tissues of the respiratory tract. Consequently, GAM might be a suitable antibiotic to treat bacterial respiratory infections in poultry, such as Ornithobacterium rhinotracheale. As O. rhinotracheale infections are common in turkey flocks, the aim of this study was to determine the pharmacokinetic (PK) parameters of GAM in plasma, lung tissue, and pulmonary epithelial lining fluid (PELF) of turkeys and to correlate them with pharmacodynamic (PD) characteristics (PK/PD). The animal experiment was performed with 64 turkeys, which received either a subcutaneous (SC, n = 32) or an oral (PO, n = 32) bolus of 6 mg GAM/kg body weight (BW). GAM concentrations in plasma, lung tissue, and PELF were measured at different time points post administration (p.a.), and PK characteristics were determined using non-compartmental modeling. The maximum plasma concentration after PO administration was ten-fold lower than after SC injection (0.087 and 0.89 μg/mL, respectively), whereas there was no difference in lung concentrations between both routes of administration. However, lung concentrations at day 1 p.a. were significantly higher than plasma levels for both routes of administration (2.22 and 3.66 μg/g for PO and SC, respectively). Consequently, lung/plasma ratios were high, up to 50 and 80 after PO and SC administration, respectively. GAM could not be detected in PELF, although this might be attributed to the collection method of PELF in birds. The GAM minimum inhibitory concentration (MIC) was determined for 38 O. rhinotracheale strains; MIC50 and MIC90 were 2 and >32 μg/mL, respectively. PK/PD correlation for lung tissue demonstrated that the time above the MIC90 of the susceptible population (2 μg/mL) was 1 day after PO bolus and 3.5 days after SC administration. The area under the curve (AUClast)/MIC ratios for lung tissue after SC and PO administration were 233 and 90, respectively. To conclude, GAM is highly distributed to lung tissue in turkey poults, suggesting that it has the potential to be used to treat respiratory infections such as O. rhinotracheale.

Development and validation of a liquid chromatography–tandem mass spectrometry method for the quantitative determination of gamithromycin in animal plasma, lung tissue and pulmonary epithelial lining fluid

A sensitive and specific method for the quantitative determination of gamithromycin in animal plasma, lung tissue and pulmonary epithelial lining fluid (PELF) using liquid chromatography combined with heated electrospray ionization tandem mass spectrometry (LC–MS/MS) was developed. The sample preparation was rapid, straightforward and consisted of a deproteinization and phospholipid removal step using an Oasis® Ostro™ 96-well plate (chicken, turkey and calf plasma) or HybridSPE®-Phospholipid SPE cartridges (pig plasma and turkey lung tissue), while a liquid–liquid extraction with diethyl ether in alkaline medium was used for PELF of turkey poults. Chromatography was performed on a C18 Hypersil GOLD column using 0.01M ammonium acetate in water with a pH of 9, and acetonitrile as mobile phases. The MS/MS instrument was operated in the positive electrospray ionization mode and the following selected reaction monitoring transitions were monitored for gamithromycin (protonated molecule>product ion): m/z 777.45>619.35 and m/z 777.45>157.80 for quantification and identification, respectively. The method was validated in-house: matrix-matched calibration graphs were prepared and good linearity (r≥0.99) was achieved over the concentration ranges tested (2.5–10,000ngmL−1 for chicken, pig and calf plasma; 5.0–2500ngmL−1 for turkey plasma; 50–10,000ngg−1 for turkey lung tissue and 20–1000ngmL−1 for turkey PELF). Limits of quantification (LOQ) were 2.5ngmL−1 for chicken, pig and calf plasma and 5.0ngmL−1 for turkey plasma, while the limits of detection (LOD) ranged between 0.007 and 0.07ngmL−1. For lung tissue and PELF, respective LOQ and LOD values of 50ngg−1 and 0.76ngg−1 (lung tissue) and 20ngmL−1 and 0.1ngmL−1 (PELF) were obtained. The results for the within-day and between-day precision, expressed as relative standard deviation (RSD), fell within the maximal RSD values. The accuracy fell within −30% to +10% (concentrations 1–10ngmL−1) or −20% to +10% (concentrations>10ngmL−1 or ngg−1) of the theoretical concentration.The method was successfully applied for the quantitative determination of gamithromycin in plasma samples of chickens, turkeys, pigs and calves; and in lung tissues and PELF of turkeys, all derived from pharmacokinetic studies in these animal species.

Intrabronchial Microdialysis: Effects of Probe Localization on Tissue Trauma and Drug Penetration into the Pulmonary Epithelial Lining Fluid.

Recent intrabronchial microdialysis data indicate that the respiratory epithelium is highly permeable to drugs. Of concern is whether intrabronchial microdialysis disrupts the integrity of the respiratory epithelium and thereby alters drug penetration into the pulmonary epithelial lining fluid (PELF). The objective of this study was to investigate the effect of intrabronchial microdialysis on the integrity of the bronchial epithelium. Microdialysis sampling in PELF in proximal (n=4) and distal bronchi (n=4) was performed after intravenous inulin and florfenicol administration in anaesthetized pigs. Inulin was used as a marker molecule of permeability of the epithelium, and florfenicol was used as test drug. Bronchial tissue was examined by histopathology (distal and proximal bronchi) and gene expression analysis (RT-qPCR, proximal bronchi) at the termination of the experiment (6.5hr). The microdialysis probe caused overt tissue trauma in distal bronchi, whereas no histopathological lesions were observed in proximal bronchi. A moderate up-regulation of the pro-inflammatory cytokines IL1B, IL6 and acute-phase reactant serum amyloid A was seen in proximal bronchi surrounding the microdialysis probes suggesting initiation of an inflammatory response. The observed up-regulation is considered to have limited impact on drug penetration during short-term studies. Inulin penetrated the respiratory epithelium in both proximal and distal bronchi without any correlation to histopathological lesions. Likewise, florfenicol penetration into PELF was unaffected by bronchial histopathology. However, this independency of pathology on drug penetration may not be valid for other antibiotics. We conclude that short-term microdialysis drug quantification can be performed in proximal bronchi without disruption of tissue integrity.

Pharmacokinetics of arbekacin in bronchial epithelial lining fluid of healthy volunteers.

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. After the initial blood sampling, arbekacin was intravenously infused into 6 healthy volunteers over 1h. Epithelial lining fluid and serum samples were collected by bronchoscopic microsampling 1, 1.5, 2, 2.5, 3, 4, 5, and 6h after the start of 200mg arbekacin infusion. Each probe sampled 10.1±5.2μl 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±1.9μg/ml and 26.0±12.2μg/ml, respectively. The ratio of the maximum drug concentration in the epithelial lining fluid to that in the serum was 0.47±0.19. The maximum concentration of epithelial lining fluid reached levels that would effectively treat most clinical strains of methicillin-resistant S. aureus.