Efficacy of aerosolized tobramycin in patients with cystic fibrosis

Pharmacokinetics and pharmacodynamics of linezolid in children with cystic fibrosis

Alternative antimicrobial regimens are needed for treatment of methicillin-resistant Staphylococcus aureus (MRSA)-associated pulmonary exacerbations in children with cystic fibrosis (CF). There are no published pharmacokinetic (PK) and pharmacodynamic (PD) data for linezolid in children with CF.

OBJECTIVES

(1) To determine the PK and PD profile of linezolid among children with CF; (2) to characterize the effect of linezolid on MRSA infection; (3) to determine the effect of age and CF transmembrane regulator (CFTR) gene mutations on drug clearance.

HYPOTHESES

Linezolid clearance is enhanced in children with CF requiring a higher dosage regimen. Age and CFTR gene mutations affect drug clearance.

METHODS

This was a retrospective cohort study; medical records of children with MRSA-associated pulmonary exacerbations treated with linezolid (10 mg/kg/dose IV every 8h) were reviewed. Linezolid peak and trough concentrations in serum were determined by high performance liquid chromatography, PK profiles determined using standard noncompartmental method, and PD indices were evaluated.

RESULTS

10 children (mean +/- SD, 10.2 +/- 5.5 years) received 14 courses of linezolid at 10 +/- 0.4 mg/kg/dose every 8h for 15.4 +/- 3.2 days. Seven had homozygous DeltaF508 CFTR mutation. Peak and trough linezolid concentrations varied widely (range, 8.4-20.5 and 0.1-11.5 mcg/mL respectively). The PK profile of children <10 years differed significantly from older patients (>or=10 years). The PK indices of children with homozygous DeltaF508 differed marginally from those with heterozygous CFTR mutations, but there were too few subjects to allow separation of age and CFTR mutations effect. No patient achieved the target PD ratio of AUC/MIC >80. MRSA persisted in sputum or throat culture after treatment with linezolid.

CONCLUSIONS

Additional PK and PD data are needed to optimize linezolid therapy in children with cystic fibrosis; it is likely that higher doses will be needed.

Bronchiectasis in children

Bronchiectasis is a chronic disease of the conducting airways that produces persistent productive cough, recurrent respiratory infectious exacerbations, and obstructive lung disease in children and adults. This article focuses on the grading and recommendations for chronic therapies of bronchiectasis caused by cystic fibrosis (CF)- and non-CF-related conditions. The scope of this article is to focus on outpatient treatment and not include as-needed treatment for mild or severe pulmonary exacerbations associated with bronchiectasis.

The new lung allocation system and its impact on waitlist characteristics and post-transplant outcomes

Historically, waiting time was the primary determinant of lung organ allocation in the United States. Under this system, waiting time grew progressively longer as the annual number of transplants reached a plateau, and every year, a considerable number of candidates died while waiting. In 2005, the lung allocation system changed; under the new system, priority for transplantation is determined by medical urgency and expected outcome. The lung allocation score is based on survival models that estimate waitlist and post-transplant survival, and reflects the net transplant benefit. Early evaluations of the new system indicate that waiting time has decreased, the total number of transplants has increased, waitlist mortality may be decreasing, and survival after transplantation remains unchanged. Over time, refinements in the lung allocation score will likely reduce waitlist mortality further and maintain or perhaps improve survival after transplantation.

Inhaled aztreonam lysine for chronic airway Pseudomonas aeruginosa in cystic fibrosis

RATIONALE

The effectiveness and safety of aztreonam lysine for inhalation (AZLI) in patients with cystic fibrosis (CF) on maintenance treatment for Pseudomonas aeruginosa (PA) airway infection was evaluated in this randomized, double-blind, placebo-controlled study.

OBJECTIVES

To evaluate the safety and efficacy of inhaled aztreonam lysine in controlling PA infection in patients with CF.

METHODS

After randomization and a 28-day course of tobramycin inhalation solution (TIS), patients (n = 211; > or =6 yr; > or =3 TIS courses within previous year; FEV(1) > or = 25% and < or =75% predicted values) were treated with 75 mg AZLI or placebo, twice or three times daily for 28 days, then monitored for 56 days. The primary efficacy endpoint was time to need for additional inhaled or intravenous antipseudomonal antibiotics. Secondary endpoints included changes in respiratory symptoms (CF Questionnaire-Revised [CFQ-R] Respiratory Scale), pulmonary function (FEV(1)), and sputum PA density. Adverse events and minimum inhibitory concentrations of aztreonam for PA were monitored.

MEASUREMENTS AND MAIN RESULTS

AZLI treatment increased median time to need for additional antipseudomonal antibiotics for symptoms of pulmonary exacerbation by 21 days, compared with placebo (AZLI, 92 d; placebo, 71 d; P = 0.007). AZLI improved mean CFQ-R respiratory scores (5.01 points, P = 0.02), FEV(1) (6.3%, P = 0.001), and sputum PA density (-0.66 log(10) cfu/g, P = 0.006) compared with placebo; no AZLI dose-response was observed. Adverse events reported for AZLI and placebo were comparable and consistent with CF lung disease. Susceptibility of PA to aztreonam at baseline and end of therapy were similar.

CONCLUSIONS

AZLI was effective in patients with CF using frequent TIS therapy. AZLI delayed time to need for inhaled or intravenous antipseudomonal antibiotics, improved respiratory symptoms and pulmonary function, and was well tolerated. Clinical trial registered with www.clinicaltrials.gov (NCT 00104520).

Update on the epidemiology and management of Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus, in patients with cystic fibrosis

PURPOSE OF REVIEW

Staphylococcus aureus is one of the first and most common pathogens to be isolated from the respiratory tract of patients with cystic fibrosis. The prevalence of respiratory tract colonization/infection with both methicillin-susceptible and methicillin-resistant S. aureus has increased over the past decade. The clinical significance of colonization/infection with these pathogens is variable, leading to numerous therapeutic strategies: primary prophylaxis, eradication, treatment of cystic fiboris pulmonary exacerbations, and treatment of methicillin-resistant S. aureus.

RECENT FINDINGS

Studies have demonstrated increased prevalence of S. aureus in clinical laboratories that use selective media. Additionally, small colony variant S. aureus has been associated with persistent infection, co-infection with Pseudomonas aeruginosa, and frequent courses of antibiotics, but this phenotype may be difficult to identify in clinical laboratories. Increased prevalence of methicillin-resistant S. aureus has led to use of oral and inhaled antibiotics in attempts to eradicate this pathogen; these studies have yielded variable results.

SUMMARY

The epidemiology of S. aureus in cystic fibrosis has changed. Studies are needed to assess the clinical significance of the increased prevalence of both methicillin-susceptible and methicillin-resistant S. aureus, and whether primary prophylaxis or new treatment/eradication protocols are effective.

Efficacy, safety, and local pharmacokinetics of highly concentrated nebulized tobramycin in patients with cystic fibrosis colonized with Pseudomonas aeruginosa

BACKGROUND AND AIM

Progressive respiratory failure due to Pseudomonas aeruginosa colonization is the most significant morbidity in patients with cystic fibrosis (CF). This trial was designed to investigate the efficacy and safety of a highly concentrated (300mg/4mL) tobramycin solution for inhalation (TSI) [Bramitob] in patients with CF and P. aeruginosa infection.

METHODS

Fifty-nine patients were randomized to receive a 4-week treatment with tobramycin or placebo administered twice daily via the Pari LC Plus nebulizer and Pari TurboBoy compressor, followed by a 4-week run-out phase. Pulmonary function (forced expiratory volume in 1 second [FEV(1)], forced vital capacity [FVC], and forced expiratory flow at the midportion of vital capacity [FEF(25-75%)]), P. aeruginosa susceptibility, microbiologic results, and in vitro minimum inhibitory concentration for 90% of strains (MIC(90)) were the efficacy outcome measures, while safety was monitored by the recording of adverse events, audiometry (bone conduction at 250-8,000Hz frequency), laboratory tests, physical examination and general health condition. The concentration of tobramycin attained in sputum was measured in a cohort of 21 patients.

RESULTS

FEV(1) significantly increased from baseline in the tobramycin group compared with no change in the placebo group: the absolute difference between groups (intent-to-treat population) of predicted normal was 13.2% at week 2 (p = 0.002) and 13.3% at week 4 (p = 0.003). Significant differences in favor of the tobramycin group were also observed for FVC and FEF(25-75%). The microbiologic results at the end of the treatment period (P. aeruginosa-negative culture, persistence, superinfection) showed a significantly better outcome in the tobramycin group compared with placebo (p = 0.033). The effects of tobramycin on pulmonary function and microbiology were not maintained at the end of the run-out phase. Mean sputum concentrations of tobramycin after the first dose (695.6 +/- 817.0 microg/mL) were similar to those measured after the last dose (716.9 +/- 799 microg/mL) and were superior to the detected specific MIC(90). The proportion of patients with drug-related adverse events was lower in the tobramycin group and no signs of renal or auditory toxicity were observed.

CONCLUSIONS

The 4-week administration of a highly concentrated TSI significantly improved pulmonary function and microbiologic outcome compared with placebo and was well tolerated. The results of this study should be confirmed in further long-term trials in larger populations.

Cystic fibrosis pulmonary guidelines: chronic medications for maintenance of lung health

RATIONALE

Cystic fibrosis is a recessive genetic disease characterized by dehydration of the airway surface liquid and impaired mucociliary clearance. As a result, individuals with the disease have difficulty clearing pathogens from the lung and experience chronic pulmonary infections and inflammation. Death is usually a result of respiratory failure. Newly introduced therapies and aggressive management of the lung disease have resulted in great improvements in length and quality of life, with the result that the median expected survival age has reached 36 years. However, as the number of treatments expands, the medical regimen becomes increasingly burdensome in time, money, and health resources. Hence, it is important that treatments should be recommended on the basis of available evidence of efficacy and safety.

OBJECTIVES

The Cystic Fibrosis Foundation therefore established a committee to examine the clinical evidence for each therapy and to provide guidance for the prescription of these therapies.

METHODS

The committee members developed and refined a series of questions related to drug therapies used in the maintenance of pulmonary function. We addressed the questions in one of three ways, based on available evidence: (1) commissioned systematic review, (2) modified systematic review, or (3) summary of existing Cochrane reviews.

CONCLUSIONS

It is hoped that the guidelines provided in this article will facilitate the appropriate application of these treatments to improve and extend the lives of all individuals with cystic fibrosis.

High-throughput screens for small-molecule inhibitors of Pseudomonas aeruginosa biofilm development

Pseudomonas aeruginosa is both a model biofilm-forming organism and an opportunistic pathogen responsible for chronic lung infections in cystic fibrosis (CF) patients and infections in burn patients, among other maladies. Here we describe the development of an efficient high-throughput screen to identify small-molecule modulators of biofilm formation. This screen has been run with 66,095 compounds to identify those that prevent biofilm formation without affecting planktonic bacterial growth. The screen is a luminescence-based attachment assay that has been validated with several strains of P. aeruginosa and compared to a well-established but low-throughput crystal violet staining biofilm assay. P. aeruginosa strain PAO1 was selected for use in the screen both because it forms robust biofilms and because genetic information and tools are available for the organism. The attachment-inhibited mutant, strain PAO1 DeltafliC, was used as a screening-positive control. We have also developed and validated a complementary biofilm detachment assay that can be used as an alternative primary screen or secondary screen for the attachment screening-positive compounds. We have determined the potencies of 61 compounds against biofilm attachment and have identified 30 compounds that fall into different structural classes as biofilm attachment inhibitors with 50% effective concentrations of less than 20 microM. These small-molecule inhibitors could lead to the identification of their relevant biofilm targets or potential therapeutics for P. aeruginosa infections.

Pharmacokinetics of inhaled monodisperse beclomethasone as a function of particle size

AIMS

For optimal efficacy, antiasthma drugs should be delivered to the desired region in the airways. To date, the optimal particle size for steroids in adults is not known. The aim of the study was to evaluate the pulmonary bioavailability for inhaled beclomethasone dipropionate (BDP) aerosols of different particle sizes.

METHODS

In a randomized single-blind crossover trial, 10 mild asthmatic patients inhaled monodisperse BDP aerosols with mass median aerodynamic diameters (MMADs) of 1.5, 2.5 and 4.5 microm. Gastrointestinal absorption was blocked by activated charcoal. Plasma concentrations of 17-beclomethasone monopropionate (17-BMP) were measured by liquid chromatography plus mass spectrometry.

RESULTS

Aerosols with MMADs of 1.5 microm, 2.5 microm, and 4.5 microm gave mean maximum concentrations (C(max)) of 17-BMP of 475 pg ml(-1), 1300 pg ml(-1), and 1161 pg ml(-1), respectively. The area under the curve (AUC) values of 17-BMP for MMADs of 1.5 microm, 2.5 microm, and 4.5 microm were 825 pg ml(-1) h, 2629 pg ml(-1) h, and 2276 pg ml(-1) h, respectively. The mean terminal half-time of 17-BMP for all three aerosol sizes was around 1.5 h.

CONCLUSIONS

Monodisperse BDP aerosols with a MMAD of 1.5 microm gave two-three fold lower values for C(max) and AUC than those with MMADs of 2.5 and 4.5 microm.

Tobramycin solution for inhalation in cystic fibrosis patients: a review of the literature

Cystic fibrosis patients suffer increased sputum production and a notable decline in respiratory function throughout the progression of their disease. Patients are left vulnerable to respiratory colonization/infection from a number of pathogens, including Pseudomonas aeruginosa. At present, the only antibiotic formulation that is FDA approved for aerosolized delivery is tobramycin solution for inhalation (TSI). TSI allows for targeted antibiotic delivery to the lungs and is indicated for maintenance therapy in cystic fibrosis patients infected with P. aeruginosa. Studies demonstrate that cyclical treatment with TSI is associated with an increase in respiratory function and a decrease in sputum density in cystic fibrosis patients. Additional benefits include fewer hospitalizations and a decreased need for systemic antibiotics. However, because of the need for chronic administration, issues such as emergence of resistant organisms and toxicity are a potential concern and have also been evaluated. This review details the pharmacology of TSI and literature involving its use in cystic fibrosis patients.

Bioelectric effects of quinine on polarized airway epithelial cells

Quinine has been increasingly utilized as a placebo in cystic fibrosis (CF) clinical trials, including those leading to FDA approval of inhaled tobramycin, recent studies of anti-inflammatory aerosols such as glutathione, and clinical testing of hypertonic saline aerosols to augment mucous clearance. The drug effectively masks taste of experimental therapeutics, but could also confer changes in processes contributing to CF pathogenesis, including chloride secretion and paracellular ion permeability. In the Ussing chamber, concentrations of quinine (1 mg/ml) anticipated in the airways of CF subjects after aerosolization led to changes in chloride transport in Calu-3 (airway serous glandular) cell monolayers. Tissue resistance was significantly disrupted by the compound in both Calu-3 and primary airway epithelial cells in vitro. Lower doses of quinine (between 10 and 100 microg/ml) strongly inhibited the chloride secretory mechanism that utilizes CFTR, and forskolin activated I(SC) was reduced by approximately 24% and 44% in the presence of 10 and 100 microg/ml quinine, respectively. Our findings indicate that quinine disrupts airway epithelial functional integrity and blocks transepithelial chloride transport. The use of quinine as a taste-masking agent may have bioelectric effects relevant to CF trials using aerosolized drug delivery.

Inhaling medicines: delivering drugs to the body through the lungs

Remarkably, with the exception of anaesthetic gases, the ancient human practice of inhaling substances into the lungs for systemic effect has only just begun to be adopted by modern medicine. Treatment of asthma by inhaled drugs began in earnest in the 1950s, and now such 'topical' or targeted treatment with inhaled drugs is considered for treating many other lung diseases. More recently, major advances have led to increasing interest in systemic delivery of drugs by inhalation. Small molecules can be delivered with very rapid action, low metabolism and high bioavailability; and macromolecules can be delivered without injections, as highlighted by the recent approval of the first inhaled insulin product. Here, we review these advances, and discuss aspects of lung physiology and formulation composition that influence the systemic delivery of inhaled therapeutics.

Advances in cystic fibrosis therapies

PURPOSE OF REVIEW

Over the past four decades, outcomes for patients with cystic fibrosis have improved dramatically. Major contributors to this improvement are a better understanding of disease pathogenesis and the systematic conduct of clinical trials evaluating new therapies designed to address these defects. This review describes recent developments in cystic fibrosis pulmonary therapies intended to treat various facets of the disease, including several treatments currently in development.

RECENT FINDINGS

The mainstays of therapy for cystic fibrosis, such as nutritional support and mechanical mucus clearance, are now supplemented with aggressive antibiotic regimens intended to suppress or eradicate bacterial colonization, anti-inflammatory agents, and new approaches that improve mucociliary clearance. Therapies in development address the underlying ion transport defect found in cystic fibrosis airways and also include small-molecule agents that restore function to the mutant cystic fibrosis transmembrane conductance regulator.

SUMMARY

Recent advances in therapies for cystic fibrosis offer the promise of improved outcomes and longer lives for patients with cystic fibrosis.

Other medications for aerosol delivery

Although aerosol therapy is most commonly used to treat asthma and COPD, there are a large number of aerosol medications now used or in development for other diseases. Mucoactive agents have long been available by aerosol, but now we have truly effective drugs to improve effective airway clearance including dornase alfa, hyperosmolar saline, and aerosol surfactant. Inhaled antibiotics are available for the treatment of cystic fibrosis, bronchiectasis and other chronic airway infections. With the development of devices that can target aerosol to the deep lung, the opportunity to deliver medications systemically by the aerosol route has become a reality. Insulin, recently approved in the US as aerosol therapy, and other peptides are systemically absorbed from the distal airway and alveolus. Aerosol gene transfer therapy to correct abnormalities associated with cystic fibrosis, primary ciliary dyskinesia and other airway diseases also holds great potential.

Advanced Techniques in the Diagnosis and Management of Infectious Pulmonary Diseases in Horses

Techniques for novel approaches to the diagnosis and management of equine pulmonary disease continue to be developed and used in clinical practice. Diagnostic techniques involving immunoassays and nucleic acid-based tests not only decrease the time in which results become available but increase the sensitivity and specificity of test results. These assays do not substitute for careful clinical evaluation but can shorten the time to a confirmed accurate diagnosis, and thus allow for early initiation of therapeutic strategies and prevention protocols. With further understanding of the molecular biology and immunology of equine pulmonary disease, diagnostic and management techniques should become further refined.

Comparison of Lung Deposition of Amikacin by Intrapulmonary Percussive Ventilation and Jet Nebulization by Urinary Monitoring

The intrapulmonary percussive ventilation (IPV), frequently coupled with a nebulizer, is increasingly used as a physiotherapy technique; however, its physiologic and clinical values have been poorly studied. The aim of this study was to compare lung deposition of amikacin by the nebulizer of the IPV device (Percussionaire; Percussionaire Corporation; Sandpoint, ID) and that of standard jet nebulization (SST; SideStream; Medic-Aid; West Sussex, UK). Amikacin was nebulized with both devices in a group of five healthy subjects during spontaneous breathing. The deposition of amikacin was measured by urinary monitoring. Drug output of both devices was measured. Respiratory frequency (RF) was significantly lower when comparing the IPV device with SST (8.2 +/- 1.6 breaths/min vs. 12.6 +/- 2.5 breaths/min, p < 0.05). The total daily amount of amikacin excreted in the urine was significantly lower with IPV than with SST (0.8% initial dose vs. 5.6% initial dose, p < 0.001). Elimination halflife was identical with both devices. Drug output was lower with IPV than with SST. The amount of amikacin delivered to the lung is sixfold lower with IPV than with SST, although a lower respiratory frequency was adopted by the subjects with the IPV. Therefore, the IPV seems unfavorable for the nebulization of antibiotics.

Progression of lung disease on computed tomography and pulmonary function tests in children and adults with cystic fibrosis

BACKGROUND

A study was undertaken to compare the ability of computed tomographic (CT) scores and pulmonary function tests to detect changes in lung disease in children and adults with cystic fibrosis (CF).

METHODS

CT scans and pulmonary function tests were retrospectively studied in a cohort of patients with CF aged 5-52 years for whom two or three CT scans at 3 year intervals were available, together with pulmonary function test results. All CT scans were scored by two observers. Pulmonary function results were expressed as percentage predicted and Z scores.

RESULTS

Of 119 patients studied, two CT scans were available in 92 patients and three in 24. CT (composite and component) scores and lung function both deteriorated significantly (p<0.02). Peripheral bronchiectasis worsened by 1.7% per year in children (p<0.0001) and by 1.5% per year in adults (p<0.0001). Bronchiectasis worsened in 68 of 92 patients while forced expiratory volume in 1 second (FEV1) worsened in 54 of 92 patients; bronchiectasis also deteriorated in 27 patients with stable or improving FEV1. The CT score (and its components) and pulmonary function tests showed similar rates of deterioration in adults and children (p>0.09).

CONCLUSION

The peripheral bronchiectasis CT score deteriorates faster and more frequently than lung function parameters in children and adults with CF, which indicates that pulmonary function tests and CT scans measure different aspects of CF lung disease. Our data support previous findings that the peripheral bronchiectasis CT score has an added value to pulmonary function tests in monitoring CF lung disease.

Improving rate of decline of FEV1 in young adults with cystic fibrosis

BACKGROUND

CF is characterised by a progressive decline in lung function; reductions in this decline are often used as a measure of success in clinical trials. With improvements in treatment it may be that there has been a temporal shift in the pattern of the disease.

METHODS

318 patients born in five successive cohorts and attending a specialist clinic with at least two routine measurements of lung function made between the ages of 18 and 22 were included. The declines in their lung function were estimated and compared.

RESULTS

The mean (SE) slopes for percentage predicted forced expiratory volume in 1 second (FEV(1)) and forced vital capacity (FVC) were -1.53 (0.36)% and -1.27 (0.34)%, respectively (NS). The annual deterioration in FEV(1) was -2.49%, -1.99% -2.20%, -1.65%, and -0.65% from the earliest to the most recent birth cohort; a similar pattern was observed for changes in FVC. There were no differences between male and female patients. Patients infected with Pseudomonas had a greater average decline in FEV(1) (-1.6% v -1.1%).

CONCLUSIONS

The rates of decline in lung function in young adults with CF have diminished with successive birth cohorts. This has important implications for the design of clinical studies in this disease.

Aerosolised antibiotics: a critical appraisal of their use

Aerosolised antimicrobial agents have been used in clinical practice since the 1950s. The main advantage of this route of administration is the targeted drug delivery to the site of infection in the lung. Exploitation of this targeted delivery can yield high concentrations at the site of infection/colonisation while minimising systemic toxicities. It is important to note that the ability of a drug to reach the target area in the lung effectively is dependent on a number of variables, including the nebuliser, patient technique, host anatomy and disease-specific factors. The most convincing data to support the use of aerosolised antimicrobials has been generated with tobramycin solution for inhalation (TOBI, Chiron Corp.) for maintenance treatment in patients with cystic fibrosis. In addition to cystic fibrosis, the use of aerosolised antimicrobials has also been studied for the treatment or prevention of a number of additional disease states including non-cystic fibrosis bronchiectasis, ventilator-associated pneumonia and prophylaxis against pulmonary fungal infections. Key studies evaluating the benefits and shortcomings of aerosolised antimicrobial agents in these areas are reviewed. Although the theory behind aerosolised administration of antibiotics seems to be sound, there are limited data available to support the routine use of this modality. Owing to the gaps still existing in our knowledge base regarding the routine use of aerosolised antibiotics, caution should be exercised when attempting to administer antimicrobials via this route in situations falling outside clearly established indications such as the treatment of patients with cystic fibrosis or Pneumocystis pneumonia.

Nebulized antibiotic therapy: the evidence

The main indications for nebulized antibiotic use are as maintenance therapy for patients with chronic Pseudomonas aeruginosa infection and in treatment protocols aimed at eradicating early P. aeruginosa infection. Daily nebulized antibiotic therapy has been used extensively in Europe for the last 25 years and recently in North America following the introduction of tobramycin solution for inhalation (TSI). The antibiotic is delivered directly to the site of infection, maximizing its efficacy and reducing its potential for toxicity. The efficacy of nebulized antibiotic therapy has been confirmed by meta-analyses of early studies which usually involved only small numbers of patients, and recently by large scale randomized control trials. These studies have shown that regular aerosolized antibiotic treatment results in improved respiratory function, less hospital admissions and respiratory exacerbations, and a significant reduction in the load of P. aeruginosa respiratory tract infection. Concerns about increasing bacterial resistance do not yet seem to have had any clinical impact. Successful eradication of early P. aeruginosa infection has been reported with nebulized colistin (in combination with oral ciprofloxacin), tobramycin and TSI. No advantage has been shown in studies comparing nebulized and intravenous antibiotics versus intravenous antibiotics alone in the treatment of acute respiratory exacerbations. Inhalation of antibiotics may provoke bronchospasm and patients should be assessed before and after treatment prior to continuing long-term therapy at home.

Breath sulfides and pulmonary function in cystic fibrosis

We have determined the concentrations of carbonyl sulfide (OCS), dimethylsulfide, and carbon disulfide (CS(2)) in the breath of a group of cystic fibrosis (CF) patients and one of healthy controls. At the detection sensitivity in these experiments, room air always contained measurable quantities of these three gases. For each subject the inhaled room concentrations were subtracted from the time-coincident concentrations in exhaled breath air. The most significant differences between the CF and control cohorts in these breath-minus-room values were found for OCS. The control group demonstrated a net uptake of 250 +/- 20 parts-per-trillion-by-volume (pptv), whereas the CF cohort had a net uptake of 110 +/- 60 pptv (P = 0.00003). Three CF patients exhaled more OCS than they inhaled from the room. The OCS concentrations in the CF cohort were strongly correlated with pulmonary function. The dimethylsulfide concentrations in breath were greatly enhanced over ambient, but no significant difference was observed between the CF and healthy control groups. The net (breath minus room) CS(2) concentrations for individuals ranged between +180 and -100 pptv. They were slightly greater in the CF cohort (+26 +/- 38 pptv) vs. the control group (-17 +/- 15 pptv; P = 0.04). Lung disease in CF is accompanied by the subsistence of chronic bacterial infections. Sulfides are known to be produced by bacteria in various systems and were therefore the special target for this investigation. Our results suggest that breath sulfide content deserves attention as a noninvasive marker of respiratory colonization.

Use of Pseudomonas biofilm susceptibilities to assign simulated antibiotic regimens for cystic fibrosis airway infection

OBJECTIVES

Increasing evidence indicates that Pseudomonas aeruginosa grows as a biofilm in the lungs of cystic fibrosis (CF) patients. In contrast, the bacterial inoculum used in conventional susceptibility testing is composed of planktonic cells. As a prelude to a clinical trial of biofilm susceptibility testing in CF, simulated antibiotic regimens based on either biofilm or conventional susceptibility testing of CF patient isolates were compared.

PATIENTS AND METHODS

Biofilm and conventional susceptibilities were determined for P. aeruginosa isolate sets from 40 CF patients. An algorithm was used to assign simulated regimens of two anti-pseudomonal antibiotics for each patient/susceptibility method dataset. For agents with equivalent activity, the algorithm included a drug selection hierarchy, the rationale for which was suppression of chronic infection. Substitution of an alternative hierarchy, based on treatment of acute exacerbation, was used to evaluate the robustness of the regimen assignments.

RESULTS

For both drug-ranking schemes, all 40 simulated regimens based on conventional susceptibilities included a beta-lactam antibiotic. In contrast, based on biofilm testing, only 43% of chronic regimens and 65% of acute regimens included a beta-lactam. Moreover, the conventional and biofilm regimens assigned to individual patients were discordant, with only 20% and 40% of chronic and acute regimens, respectively, consisting of drugs in the same two mechanistic classes by both methods.

CONCLUSIONS

Biofilm susceptibility testing of CF P. aeruginosa isolate sets leads to different antibiotic assignments than conventional testing, with no single two-drug regimen predicted to provide optimal anti-biofilm activity against the majority of isolate sets.

Cystic fibrosis since 1938

Cystic fibrosis (CF) was distinguished from celiac disease in 1938. Then, it was a pathologic diagnosis, life expectancy was approximately 6 months, and the autosomal recessive disease was believed to arise from abnormal mucus plugging exocrine ducts. Death often occurred from lung infection. Discovery of the sweat electrolyte defect in 1953 and standardization of the sweat test in 1959 allowed identification of milder cases, and CF was no longer considered only a disorder of mucus. In 1955, establishment of centers with programs of aggressive, comprehensive care initiated striking improvement in longevity. The pillars of care established then (attention to nutrition, airway clearance, treatment of lung infection) remain today. In 1983, chloride transport was identified as the basic physiologic CF defect, accompanied by increased sodium reabsorption. In 1980, we learned that inflammation contributes independently to lung disease and constitutes an independent therapeutic target. In 1989, the discovery of the CF gene demonstrated the basic defect to be in a cAMP-regulated chloride channel. This afforded new diagnostic tests, opportunities for research, and prospects for using the gene as therapy. Since then, substantial advances in basic and clinical research catalyzed therapeutic improvements: median survival age now exceeds 30 years. The Cystic Fibrosis Foundation center network provides not only opportunity to conduct clinical trials but also means to disseminate new therapies. In the future, treatments directed at the basic defect can be expected, with concomitant improvements in morbidity and mortality.

Hypermutation is a key factor in development of multiple-antimicrobial resistance in Pseudomonas aeruginosa strains causing chronic lung infections

Pseudomonas aeruginosa is the most relevant pathogen producing chronic lung infections in patients with chronic underlying diseases such as cystic fibrosis (CF), bronchiectasis, and chronic obstructive pulmonary disease (COPD). Hypermutable (or mutator) P. aeruginosa strains, characterized by increased (up to 1,000-fold) spontaneous mutation rates due to alterations of the DNA mismatch repair (MMR) system have been found at high frequencies in the lungs of CF patients, but their role in other chronic processes is still unknown. Sixty-two P. aeruginosa isolates from 30 patients with underlying non-CF chronic respiratory diseases (22 with bronchiectasis and 8 with COPD) and documented chronic infection were studied. Antibiotic susceptibility profiles and mutation frequencies were determined, and complementation assays using the cloned wild-type mutS gene and molecular epidemiology studies (pulsed-field electrophoresis, [PFGE]) were performed with these strains. Thirty-three (53%) of the isolates were hypermutable, and 17 (57%) of the 30 patients were colonized by hypermutable strains. Strains from 11 of the 17 patients were found to be defective in the MMR mutS gene by complementation assays. Interpatient transmission of strains was ruled out by PFGE. Multiple-antimicrobial resistance was documented in 42% of the hypermutable strains in contrast to 0% resistance in the nonhypermutable strains (P < 0.0001). Hypermutable P. aeruginosa strains are extremely prevalent in chronic infections in contrast to what has been described in acute processes, suggesting a role of hypermutation in bacterial adaptation for long-term persistence. Furthermore, hypermutation is found to be a key factor for the development of multiple-antimicrobial resistance, and therefore these findings are expected to have important consequences for the treatment of chronic infections.

Renal and Vestibular Toxicity Due to Inhaled Tobramycin in a Lung Transplant Recipient

Chronic rejection is the major hurdle to long-term survival after lung transplantation. Endobronchial infection with Pseudomonas aeruginosa is common in patients with chronic rejection and this may further contribute to deterioration of the allograft. Inhaled tobramycin is commonly used to treat P aeruginosa airways infection in patients with cystic fibrosis. The safety of inhaled tobramycin in transplant recipients, however, has not been established. We describe the first report of a lung transplant recipient who developed renal failure and vestibular injury after receiving inhaled tobramycin. We review the literature regarding the safety of inhaled tobramycin and discuss potential mechanisms that may promote systemic toxicity in transplant recipients.

Misleading High Tobramycin Plasma Concentrations Can Be Caused by Skin Contamination of Fingerprick Blood Following Inhalation of Nebulized Tobramycin (TOBI??)

We observed unexpected high plasma concentrations of tobramycin (48.5 and 28.1 mg/L) in fingerprick blood samples after the nebulization of tobramycin solution for inhalation (tobramycin 300 mg/5 mL, TOBI by 2 young children aged 3 years. To investigate whether dermal contamination could be the source of error, 3 adult volunteers were present during another nebulization by a third child (age 2 years). The volunteers had exposure to tobramycin by handling the nebulizer or the nebule and also by inhalation from holding the child and being in close proximity while TOBI was being administered. Five blood samples by fingerprick and 2 by venipuncture were collected and assayed for tobramycin concentration. On each occasion the site was swabbed with alcohol wipes to mimic standard patient sampling methods. One site was resampled after cleaning of hands with 2% chlorhexidine gluconate and water. Tobramycin concentrations from venipuncture 1-2 hours after nebulization were all <0.2 mg/L except for 1 result of 1.2 mg/L. The tobramycin concentrations from fingerpricks before hand washing varied between 6.8 and 172 mg/L, and after hand washing between 0.3 and 17.6 mg/L. Contamination of fingers with tobramycin is likely to have caused the error in the 2 initial cases and did cause misleadingly elevated levels in the adult volunteers. We caution that therapeutic drug monitoring of nebulized tobramycin should not be done by fingerprick sampling, and care should be taken to avoid contamination of the venipuncture site.

Emerging drug treatments for cystic fibrosis

Cystic fibrosis (CF) is one of the most common life-shortening inherited disorders. Mutations in the cystic fibrosis transmembrane regulator (CFTR) gene disrupt the localisation and function of the cAMP-mediated chloride channel. Most of the morbidity and mortality arise from the lung disease which is characterised by excessive inflammation and chronic infection. Research into the mechanisms of wild-type and mutant CFTR biogenesis suggest that multiple drug targets can be identified. This review explores the current understanding of the nature of the different mutant CFTR forms and the potential for repair of the chloride channel defect. High-throughput screening, pharmacogenomics and proteomics bring recent technological advances to the field.

Histatin-derived peptides: potential agents to treat localised infections

Histatins are a family of histidine-rich, cationic peptides composed of up to 38 amino acids. They are secreted by the salivary glands of humans and some subhuman primates and are thought to be part of the host defence system in the oral cavity. Histatins exhibit in vitro activity against both bacteria and yeast, common to other antimicrobial peptides. Because of these activities, histatin-based peptides could play an important role in the treatment and prevention of infectious diseases. A 12 amino acid amidated fragment of histatin 5, designated P-113, has been identified as the smallest fragment that retains antimicrobial activity comparable to the parent compound. Animal studies and human clinical trials showed that P-113 has potential in preventing the development of gingivitis, with no adverse side effects. Histatin peptides also could be used for other therapeutic applications in which the infection is localised and accessible via topical delivery, such as treatment of candidiasis (thrush) and mucositis in the oral cavity, skin infections and treatment of lung infections afflicting cystic fibrosis patients.

Deposition of coarse particles in cystic fibrosis: model predictions versus experimental results

In patients with cystic fibrosis (CF), the lung regions most affected by infection are presumed to be poorly ventilated and, hence, difficult to treat with inhaled therapeutic aerosols. Current dosimetric models do not adequately describe regional particle deposition in CF. We have developed a multiple-path particle deposition model and compared model predictions with the observed pattern of coarse particle (5 microm, mass median aerodynamic diameter) deposition in ten CF patients and eight healthy volunteers. Our model divides the lung into quadrants, separated at lobar bronchi, representing apical and basal lung regions. The volume and ventilation of quadrants were experimentally determined from a xenon equilibrium and multi-breath washout, respectively. Regional ventilation in the healthy lung was assumed to be determined largely by regional compliance. In CF patients, the deviations in regional ventilation from that observed in the healthy subjects were assumed to be due to regional resistance. A "custom" lung morphology was calculated for each subject based on their lung volume (functional residual capacity plus one-half tidal volume) and ventilation to each quadrant. Input parameters for particle deposition calculations were "custom" lung morphology, breathing pattern, and inhaled particle size. Relative to healthy subjects, the CF patients had reduced ventilation to the apices and increased ventilation to the bases of the lung. In healthy subjects, the general pattern of particle deposition followed ventilation. However, in the CF patients, the model predicted increased particle deposition in the large airways of the apices (an obstructed and poorly ventilated region) and to a lesser extent in the basal lung (relatively healthier and better-ventilated region), whereas particle deposition in the parenchyma was only increased in the basal lung and was decreased or absent in the apical lung. Our modeling strategy improves estimates of regional aerosol deposition and may be useful for predicting breathing conditions and particle size for optimal drug delivery in a given CF patient.

Inhaled tobramycin in non-cystic fibrosis patients with bronchiectasis and chronic bronchial infection with Pseudomonas aeruginosa

BACKGROUND

Non-cystic fibrosis (CF) patients with bronchiectasis usually develop chronic bronchial infection with Pseudomonas aeruginosa (PA) that is related to worsening lung function and increased morbidity and mortality.

OBJECTIVE

To determine whether direct aerosol delivery of tobramycin to the lower airways may control infection and produce only low systemic toxicity.

METHODS

A double-blind, placebo-controlled crossover trial involving 30 patients was conducted to determine the clinical effectiveness and safety of 6-month tobramycin inhalation therapy. Patients received 300 mg of aerosolized tobramycin or placebo twice daily in 2 cycles, each for 6 months, with a one-month washout period. The number of exacerbations, number of hospital admissions, number of hospital admission days, antibiotic use, pulmonary function, quality of life, tobramycin toxicity, density of PA in sputum, emergence of bacterial resistance, and emergence of other opportunistic bacteria were recorded.

RESULTS

The number of admissions and days of admission (mean +/- SD) during the tobramycin period (0.15 +/- 0.37 and 2.05 +/- 5.03) were lower than those during the placebo period (0.75 +/-1.16 and 12.65 +/- 21.8) (p < 0.047). A decrease in PA density in sputum was associated with tobramycin administration in the analysis of the first 6-month cycle (p = 0.038). No significant differences were observed in the number of exacerbations, antibiotic use, pulmonary function, and quality of life. The emergence of bacterial resistance and other bacteria did not differ between the 2 periods of study. Inhaled tobramycin was associated with bronchospasm in 3 patients, but not with detectable ototoxicity or nephrotoxicity.

CONCLUSIONS

Aerosol administration of high-dose tobramycin in non-CF bronchiectatic patients for endobronchial infection with PA appears to be safe and decreases the risk of hospitalization and PA density in sputum. Nevertheless, pulmonary function and quality of life are not improved, and the risk of bronchospasm is appreciable.

Pseudomonal infection in cystic fibrosis: the battle continues

Pseudomonas aeruginosa lung infection is the major cause of morbidity and mortality in patients with cystic fibrosis. Infection usually begins in childhood and is responsible for respiratory failure and death in most patients with cystic fibrosis. The organism triggers an exuberant chronic inflammatory reaction which damages the airways and leads to progressive loss of lung function. Over the last decade significant advances have been made in the understanding of the pathophysiology of cystic fibrosis airways disease. These should assist the development of new and better therapies to treat this pathogen. This review provides an overview of pseudomonal infection in cystic fibrosis, including mechanisms by which the bacteria may colonize the cystic fibrosis airway, persistence of pseudomonal infection and the biofilm mode of growth. Available treatments and possible novel approaches to therapy will be discussed.

The long-term use of inhaled tobramycin in patients with cystic fibrosis

Tobramycin nebuliser solution (TNS) has been investigated in several clinical trials, including a large, placebo-controlled study that demonstrated efficacy over a 24-week period. The open-label extension phase of this trial enabled observations to be conducted for an additional period of almost 18 months. Patients from both treatment arms (n=396) entered the open-label phase and received up to nine 28-day on, 28-day off cycles of TNS 300 mg by aerosol twice daily (b.i.d.). Mean lung function in patients who had received placebo during the double-blind phase improved during the first three cycles of the open-label treatment. However, lung function in these patients did not recover to the levels seen in those patients who had received TNS throughout the double-blind and open-label phases. In both groups of patients, improvement was maintained during the study. Greater improvements were seen in adolescents compared with older patients. Adverse events were generally uncommon, with a notably lower incidence of fever, anorexia, abdominal pain and vomiting than was observed in the double-blind phase among patients who received placebo, and a generally low incidence of tinnitus. We conclude that long-term TNS administration is safe and effective.

Treatment with tobramycin solution for inhalation reduces hospitalizations in young CF subjects with mild lung disease

Our objective was to study the effect of tobramycin solution for inhalation (TSI; TOBI, Chiron Corp.) on lung function decline rate in 400 young persons with cystic fibrosis (CF) and mild lung disease. Effects on hospitalization, antibiotic use, school days missed, and nutritional status also were determined. This was an open-label, randomized (stratified by sex and age group, i.e., 6-10 and 11-15 years), parallel-group, multicenter study. Routine subject management (control group) was compared to routine management plus 28 days of twice-daily TSI inhalation, followed by 28 days off the drug (TSI group) for 56 weeks. Primary efficacy endpoints included rate of lung function decline (as measured by forced expiratory volume in 1 sec; FEV(1)), hospitalization, and concomitant antibiotic use. Safety was assessed by analysis of treatment-emergent adverse events. Only 184 of 400 planned subjects were recruited and randomized (93 to the TSI group, and 91 to the control group). Enrollment was ended after 2 years because of difficult recruitment. An interim safety review showed a 2.42-fold risk of respiratory hospitalization for control group subjects (P = 0.020), and the study was terminated. Sixty-three subjects (34.2%) completed the entire study (30 in the TSI group, or 32.3%; and 33 in the control group, or 36.3%). Significantly fewer TSI subjects were hospitalized for worsening of respiratory symptoms (11.0% vs. 25.6%; P = 0.011), and fewer TSI subjects were hospitalized overall (16.5% vs. 27.8%; P = 0.065). Fewer TSI subjects received antibiotics other than the study drug (78.0% vs. 95.6%), and significantly fewer received oral antibiotics (76.9% vs. 91.1%; P = 0.009). No other safety or adverse event differences were observed. In conclusion, significant reductions in respiratory hospitalizations, concomitant antibiotic use, and a trend towards improvement in percent predicted forced expiratory flow (FEF(25-75)) provide evidence of a clinical benefit of TSI use in young persons with CF and mild lung disease. An effect on lung function decline rate could not be evaluated as planned, due to inadequate enrollment and early study termination.

Vestibular toxicity due to inhaled tobramycin in a patient with renal insufficiency

Inhaled tobramycin is being used increasingly in patients with cystic fibrosis and other forms of bronchiectasis for treatment of bronchial colonization with Pseudomonas aeruginosa. The goal of inhaled antibiotics is to provide maximal concentrations at the site of infection without risking systemic toxicity. We report an unusual case of reversible vestibular toxicity due to inhaled tobramycin in a patient with renal failure who was undergoing hemodialysis. Although systemic absorption after inhaled tobramycin is reportedly negligible, no recommendations have been published regarding monitoring of serum concentrations in patients receiving this form of therapy. We suggest that clinicians consider monitoring serum concentrations of tobramycin in patients at risk of renal toxicity and/or ototoxicity, such as those with predisposing renal or otologic compromise. Further studies in at-risk patients are needed to determine the optimal frequency and timing of such monitoring.

Refractory chronic rhinosinusitis: pathophysiology and management of chronic rhinosinusitis persisting after endoscopic sinus surgery

Refractory chronic rhinosinusitis (RCRS) is defined as persistence of signs and symptoms of chronic rhinosinusitis, despite technically adequate endoscopic sinus surgery. Rather than a simple, prolonged bout of acute sinusitis, it instead appears to be secondary to an interaction of a susceptible host with the outside environment. Inflammatory responses to colonizing bacteria appear to be responsible for a significant portion of the pathophysiology. Reduction of bacterial load and inflammation of the mucosa play an important role in controlling the disease. Novel treatment strategies, with an emphasis on topical therapies, seem to offer optimal management. In this review, current concepts on the pathophysiology and current therapies available for RCRS are outlined. A practical management strategy based on the author's personal experience draws upon these concepts, and is detailed in this review of an unusual topic.

Clinical Evaluation of the Delivery and Safety of Aerosolized Liposomal 9-Nitro-20(S)-Camptothecin in Patients with Advanced Pulmonary Malignancies

PURPOSE

The purpose is to evaluate the feasibility and safety of aerosol administration of the topoisomerase I inhibitor, 9-nitrocamptothecin, in a liposome formulation, and to recommend a dosage for a Phase II trial for an 8-week daily treatment schedule.

EXPERIMENTAL DESIGN

Patients with primary or metastatic lung cancer received aerosolized liposomal 9-nitrocamptothecin for 5 consecutive days/week for 1, 2, 4, or 6 weeks followed by 2 weeks of rest to determine feasibility. For the Phase I part, the dose was increased stepwise from 6.7 up to 26.6 micro g/kg/day Monday to Friday for 8 weeks followed by 2 weeks of rest.

RESULTS

Twenty-five patients received treatment. The mean baseline forced expiratory volume in 1 second for all patients was 85% of predicted. A dose-limiting toxicity was chemical pharyngitis seen after 1 week in 2 of 2 patients at 26.6 micro g/kg/day. At 20.0 micro g/kg/day, grade 2 and 3 fatigue prompting a dose reduction was seen after 4 weeks in 2 of 4 patients. Grade 2 toxic effects included nausea/vomiting (9 patients), cough and bronchial irritation (6 patients), fatigue (5 patients), anemia (4 patients), neutropenia (2 patients), anorexia (1 patient), and skin rash around the face mask (1 patient). 9-Nitro-20(S)-camptothecin (9NC) was absorbed systemically. Partial remissions were observed in 2 patients with uterine cancer, and stabilization occurred in 3 patients with primary lung cancer.

CONCLUSIONS

Aerosol administration of liposomal 9NC was found to be feasible and safe. 9NC delivered as an aerosol was detected in patient's plasma shortly after the start of treatment. The recommended dose for Phase II studies is 13.3 micro g/kg/day (equivalent to 0.5 mg/m(2)/day), which constitutes two consecutive 30-min nebulizations/day from a nebulizer reservoir with 4 mg of 9NC in 10 ml of sterile water, Monday to Friday for 8 weeks every 10 weeks.

Improved outcomes of patients with cystic fibrosis admitted to the intensive care unit

BACKGROUND

Invasive mechanical ventilation (IMV) has been previously associated with a poor outcome for patients with cystic fibrosis (CF), but with improved survival and the availability of lung transplantation intensive care unit (ICU) admission is being increasingly considered. This study aimed to review the outcomes of adult CF patients admitted to ICU, and to identify factors that may have influenced outcomes.

METHODS

A retrospective audit was conducted of CF patients admitted to ICU. Anthropometric data, spirometry, nutritional status, sputum microbiology, arterial blood gas tensions, and mode of ventilation used were recorded. Immediate and 1-year survival and lung transplantation utilisation were recorded.

RESULTS

Twenty patients were admitted to ICU and nine (45%) survived to hospital discharge. Five of the nine survivors had potentially reversible conditions. Four patients admitted with respiratory exacerbations alone who survived, were maintained on non-invasive ventilation (NIV). The relative risk of deaths for patients with a BMI < 18 and a FEV1 < 24% predicted were 3.25 (1.27-3.25), and 3.68 (1.11-16.33), respectively.

CONCLUSIONS

The outcome of patients with CF admitted to ICU has improved, with 45% of the patients in this study surviving to hospital discharge. Five of these survivors underwent successful lung transplantation. Long-term use of NIV post discharge may have contributed to this favourable outcome. A BMI < 18 and FEV1 < 24% predicted were associated with a significantly higher relative risk of death.

Bringing new treatments to the bedside in cystic fibrosis

The discovery of the cystic fibrosis transmembrane conductance regulator gene in 1989 led to a dramatic increase in the understanding of the molecular basis of CF. Increased knowledge has provided the opportunity to target drug development at correcting the basic defect either by gene therapy or pharmacological modulation of the abnormal physiological processes. Development of new medications for the CF population poses many challenges. The discovery and development of new medications is always time consuming and expensive. Since CF affects a small population worldwide, the potential for a drug company to profit from a new treatment is limited. In addition, each new therapy must have an additional and proven benefit to be attractive to clinicians and consumers, otherwise it will not be commercially viable. Demonstrating clinical benefit is problematic as a limited number of patients are available to participate in clinical trails and outcome measures, such as length of life, are hard to measure. In this review we will illustrate these challenges by discussing the development of treatments which have successfully reached the bedside and those that were unsuccessful.

New medical management techniques for acute exacerbations of chronic rhinosinusitis

In the past 2 years, intranasal nebulized medications have emerged as a widely prescribed treatment for medical management of chronic rhinosinusitis. This represents an innovative and advanced approach to treating acute exacerbations of chronic rhinosinusitis topically. The use of specially formulated medication compounds delivered by unique nebulization equipment is reviewed in the treatment of patients with chronic sinus disease. Scientific data including related upper and lower respiratory literature is included, as well as the important aspects of factors affecting nebulized medication delivery to the sinuses. The benefits, effectiveness, risks, and adverse effects of intranasal nebulized medications are also addressed. A treatment algorithm identifying appropriate use of nebulized medications in the treatment plan for chronic sinusitis patients is then presented in diagrammatic format.