The therapeutic ratio of R-albuterol is comparable with that of RS-albuterol in asthmatic patients

Indian Guidelines on Nebulization Therapy

Inhalational therapy, today, happens to be the mainstay of treatment in obstructive airway diseases (OADs), such as asthma, chronic obstructive pulmonary disease (COPD), and is also in the present, used in a variety of other pulmonary and even non-pulmonary disorders. Hand-held inhalation devices may often be difficult to use, particularly for children, elderly, debilitated or distressed patients. Nebulization therapy emerges as a good option in these cases besides being useful in the home care, emergency room and critical care settings. With so many advancements taking place in nebulizer technology; availability of a plethora of drug formulations for its use, and the widening scope of this therapy; medical practitioners, respiratory therapists, and other health care personnel face the challenge of choosing appropriate inhalation devices and drug formulations, besides their rational application and use in different clinical situations. Adequate maintenance of nebulizer equipment including their disinfection and storage are the other relevant issues requiring guidance. Injudicious and improper use of nebulizers and their poor maintenance can sometimes lead to serious health hazards, nosocomial infections, transmission of infection, and other adverse outcomes. Thus, it is imperative to have a proper national guideline on nebulization practices to bridge the knowledge gaps amongst various health care personnel involved in this practice. It will also serve as an educational and scientific resource for healthcare professionals, as well as promote future research by identifying neglected and ignored areas in this field. Such comprehensive guidelines on this subject have not been available in the country and the only available proper international guidelines were released in 1997 which have not been updated for a noticeably long period of over two decades, though many changes and advancements have taken place in this technology in the recent past. Much of nebulization practices in the present may not be evidence-based and even some of these, the way they are currently used, may be ineffective or even harmful. Recognizing the knowledge deficit and paucity of guidelines on the usage of nebulizers in various settings such as inpatient, out-patient, emergency room, critical care, and domiciliary use in India in a wide variety of indications to standardize nebulization practices and to address many other related issues; National College of Chest Physicians (India), commissioned a National task force consisting of eminent experts in the field of Pulmonary Medicine from different backgrounds and different parts of the country to review the available evidence from the medical literature on the scientific principles and clinical practices of nebulization therapy and to formulate evidence-based guidelines on it. The guideline is based on all possible literature that could be explored with the best available evidence and incorporating expert opinions. To support the guideline with high-quality evidence, a systematic search of the electronic databases was performed to identify the relevant studies, position papers, consensus reports, and recommendations published. Rating of the level of the quality of evidence and the strength of recommendation was done using the GRADE system. Six topics were identified, each given to one group of experts comprising of advisors, chairpersons, convenor and members, and such six groups (A-F) were formed and the consensus recommendations of each group was included as a section in the guidelines (Sections I to VI). The topics included were: A. Introduction, basic principles and technical aspects of nebulization, types of equipment, their choice, use, and maintenance B. Nebulization therapy in obstructive airway diseases C. Nebulization therapy in the intensive care unit D. Use of various drugs (other than bronchodilators and inhaled corticosteroids) by nebulized route and miscellaneous uses of nebulization therapy E. Domiciliary/Home/Maintenance nebulization therapy; public & health care workers education, and F. Nebulization therapy in COVID-19 pandemic and in patients of other contagious viral respiratory infections (included later considering the crisis created due to COVID-19 pandemic). Various issues in different sections have been discussed in the form of questions, followed by point-wise evidence statements based on the existing knowledge, and recommendations have been formulated.

Long-Acting β2-Agonists in Asthma: Enantioselective Safety Studies are Needed

Long-acting β2-agonists (LABAs) such as formoterol and salmeterol are used for prolonged bronchodilatation in asthma, usually in combination with inhaled corticosteroids (ICSs). Unexplained paradoxical asthma exacerbations and deaths have been associated with LABAs, particularly when used without ICS. LABAs clearly demonstrate effective bronchodilatation and steroid-sparing activity, but long-term treatment can lead to tolerance of their bronchodilator effects. There are also concerns with regard to the effects of LABAs on bronchial hyperresponsiveness (BHR), where long-term use is associated with increased BHR and loss of bronchoprotection. A complicating factor is that formoterol and salmeterol are both chiral compounds, usually administered as 50:50 racemic (rac-) mixtures of two enantiomers. The chiral nature of these compounds has been largely forgotten in the debate regarding LABA safety and effects on BHR, particularly that (S)-enantiomers of β2-agonists may be deleterious to asthma control. LABAs display enantioselective pharmacokinetics and pharmacodynamics. Biological plausibility of the deleterious effects of β2-agonists (S)-enantiomers is provided by in vitro and in vivo studies from the short-acting β2-agonist (SABA) salbutamol. Supportive clinical findings include the fact that patients in emergency departments who demonstrate a blunted response to salbutamol are more likely to benefit from (R)-salbutamol than rac-salbutamol, and resistance to salbutamol appears to be a contributory mechanism in rapid asthma deaths. More effort should therefore be applied to investigating potential enantiospecific effects of LABAs on safety, specifically bronchoprotection. Safety studies directly assessing the effects of LABA (S)-enantiomers on BHR are long overdue.

Management of severe COPD exacerbations: focus on beclomethasone dipropionate/formoterol/glycopyrronium bromide

The major determinant of the decline in lung function, quality of life, and the increased mortality risk in patients with COPD is represented by severe acute exacerbations of the disease, that is, those requiring patients’ hospitalization, constituting a substantial social and health care burden in terms of morbidity and medical resource utilization. Different long-term therapeutic strategies have been proposed so far in order to prevent and/or reduce the clinical and social impact of these events, the majority of which were extrapolated from trials initially focused on the effect of long-acting muscarinic antagonist and subsequently on the efficacy of long-acting β2-agonists in combination or not with inhaled corticosteroids. The option to employ all three classes of molecules combined, despite the limited amount of evidence in our possession, represents a choice currently proposed by international guidelines; however, current recommendations are often based mainly on observational studies or on the results of secondary outcomes in randomized controlled trials. The present narrative review evaluates the available trials that investigated the efficacy of inhaled therapy to prevent COPD exacerbations and especially severe ones, with a particular focus on beclomethasone dipropionate/formoterol/glycopyrronium bromide fixed dose combination, which is the first treatment that comprises all the three drug classes, specifically tested for the prevention of moderate and severe COPD exacerbations.

Clinical outcomes of levalbuterol versus racemic albuterol in pediatric patients with asthma: Propensity score matching approach in a medicaid population

OBJECTIVE

Racemic albuterol and levalbuterol are used to treat acute episodes of asthma. The main objective of this study was to compare levalbuterol therapy to albuterol therapy on incidence rates of subsequent emergency department (ED) visits and hospitalizations.

METHOD

We conducted a retrospective cohort study of asthmatic children who had pharmacy refills for levalbuterol/albuterol in the South Carolina Medicaid database in 2002-2011. Children receiving levalbuterol were matched to those receiving albuterol using propensity score matching technique. For ED visits and separately for hospitalizations, multivariable negative binomial regression was used to estimate the two group-specific incidence rates and the incidence rate ratio (IRR).

RESULTS

A total of 8,172 asthmatic patients aged 2-18 years were identified in the South Carolina Medicaid database. During the 12-month follow-up period, the levalbuterol group had fewer asthma-related ED visits and hospitalizations: 939 (11.49%) children had asthma-related ED visits (levalbuterol: 8.76%; albuterol: 14.21%), and 89 (1.09%) children had asthma-related hospitalizations (levalbuterol: 1.07%; albuterol: 1.12%). Comparing the levalbuterol group to the albuterol group, the adjusted IRR estimate was 0.57 (95% confidence interval [CI], 0.49-0.65) for of asthma-related ED visits, and 0.93 (95%CI, 0.99-1.63) for hospitalizations. Children filling levalbuterol also had a lower IRR of all-cause ED visit (0.88; 95%CI, 0.82-0.95), but similar IRR of all-cause hospitalizations (1.08; 95%CI, 0.82-1.42).

CONCLUSION

This observational study of children aged 2-18 demonstrated levalbuterol prescription fills were associated with reduced ED visits, but not hospitalizations. Additional research may be necessary to assess this association. Pediatr Pulmonol. 2017;52:516-523. © 2016 Wiley Periodicals, Inc.

Change in Oxygen Consumption Following Inhalation of Albuterol in Comparison with Levalbuterol in Healthy Adult Volunteers

BACKGROUND

Albuterol is the most commonly used β agonist to treat reversible lower airway obstruction. Albuterol contains a racemic mixture of two enantiomers. Levalbuterol contains the single R form enantiomer. Levalbuterol is frequently prescribed to limit cardiovascular toxicity.

OBJECTIVE

We examined changes in oxygen consumption (V'O₂) and heart rate (HR) following administration of albuterol and levalbuterol.

METHODS

This is a prospective, randomized, single-blinded, controlled study of healthy adult volunteers. Subjects separately received albuterol (5 mg) and levalbuterol (2.5 mg) aerosolized over 15 min. V'O₂ and vital signs were measured before the medications and 5, 10, 20, 40, and 60 min after.

RESULTS

We enrolled 24 volunteers with a median age of 32 years. Compared to baseline, there was a significant maximum increase in V'O₂ following administration of both albuterol (median 17% (1, 3 IQR 9, 43%) p < 0.001) and levalbuterol (median 23% (1, 3 IQR 10, 32%) p < 0.001). There was no significant difference between the maximum increase in V'O₂ following administration of albuterol compared to levalbuterol (p = 0.57). Compared to baseline, there was a significant maximal increase in HR with both albuterol (median 30% (1, 3 IQR 19, 43%) p < 0.001) and levalbuterol (median 23% (1, 3 IQR 19, 31%) p < 0.001). There was a statistically significant greater increase in maximal HR following administration of albuterol as compared to levalbuterol (p = 0.009).

CONCLUSION

Albuterol and levalbuterol both cause a significant increase in V'O₂ and HR. There was no significant difference between albuterol and levalbuterol regarding the maximum increase in V'O₂. There was a statistically significant but likely clinically insignificant difference in maximum increase in HR in patients with adequate oxygen delivery when comparing albuterol to levalbuterol.

Clinical outcomes and treatment cost comparison of levalbuterol versus albuterol in hospitalized adults with chronic obstructive pulmonary disease or asthma

PURPOSE

Results of a prospective study comparing clinical outcomes and costs of levalbuterol versus albuterol therapy for exacerbations of asthma or chronic obstructive pulmonary disease (COPD) are presented.

METHODS

In a single-center open-label study, selected adults hospitalized for asthma or COPD exacerbations over a 21-month period were randomly assigned to receive levalbuterol 1.25 mg three times daily (n = 55) or albuterol 2.5 mg four times daily (n = 57); dosage reductions and other respiratory therapies were permitted. Study outcomes included scheduled and rescue nebulizations, total treatment costs, hospital length of stay, and change in heart rate from baseline.

RESULTS

The numbers of scheduled nebulizations were similar in the levalbuterol and albuterol groups (mean ± S.D., 19.6 ± 13.4 versus 20.7 ± 14.4; p = 0.692), as were the numbers of rescue nebulizations (mean ± S.D., 0.7 ± 1.4 versus 0.8 ± 2.0; p = 0.849). The mean change from baseline in heart rate did not differ significantly between groups. Mean total treatment costs per patient were significantly greater with the use of levalbuterol ($8003, bootstrap 95% confidence interval [CI], $6628-$9379) versus albuterol ($5772, bootstrap 95% CI, $5051-$6494; p = 0.006). Hospital length of stay was significantly greater in the levalbuterol group (mean ± S.D., 8.5 ± 5.2 days versus 6.8 ± 3.6 days with albuterol use; p = 0.040).

CONCLUSION

Clinical outcomes were similar with the use of levalbuterol versus albuterol for exacerbations of COPD or asthma. On average, patients receiving levalbuterol had longer and more costly hospital stays.

Advances in acute asthma

PURPOSE OF REVIEW

The purpose of this study is to highlight some of the recent findings related with the management of acute exacerbations in the context of the emergency department setting.

RECENT FINDINGS

β₂-agonist heliox-driven nebulization significantly increased by 17% [95% confidence interval (CI) 5.2-29.4] peak expiratory flow, and decreased the rate of hospital admissions (risk ratio 0.77, 95% CI 0.62-0.98), compared with oxygen-driven nebulization. Other findings indicate that there is no robust evidence to support the use of intravenous or nebulized magnesium sulphate in adults with severe acute asthma, and that levalbuterol was not superior to albuterol regarding efficacy and safety in individuals with acute asthma. Finally, hyperlactatemia developed during the first hours of acute asthma treatment has a high prevalence, is related with the use of β₂-agonists and had no clinical consequences.

SUMMARY

After a comprehensive review of the best quality pieces of literature published in the last year, it is possible to conclude that the goals of acute asthma management remain almost unchanged.

Asthma myths, controversies, and dogma

Although the symptom complex we call asthma has been well described since antiquity, our understanding of the causes and therapy of asthma has evolved. Even with this evolution in our understanding, there are persistent myths (widely held but false beliefs) and dogma (entrenched beliefs) regarding the causes, classification, and therapy of asthma. It is sobering that some of the knowledge we hold dear today, will become the mythology of tomorrow.

Modeling and simulation to probe the pharmacokinetic disposition of pomalidomide R- and S-enantiomers

Pomalidomide, a potent novel immunomodulatory agent, has been developed as a racemic mixture of its R- and S-isomers. Pharmacokinetic (PK) analyses were conducted to determine the PK disposition of the isomers from their PK profiles in humans and monkeys. Modeling and simulation were performed to describe the observed PK profiles and explore potential differences in isomer disposition and exposure. PK profiles of S- and R-isomers were measured in a human absorption, distribution, metabolism, and excretion study after oral administration of racemate. PK profiles of S- and R-isomers were measured in monkeys after intravenous and oral administration of S- or R-isomers and pomalidomide racemate. Modeling and simulation were performed using NONMEM 7.2 (Globomax, Ellicott City, MD) to describe the observed PK profiles of S- and R-isomers in humans and monkeys. The results showed that in humans, the in vivo elimination rate of pomalidomide isomers was lower than the R-/S-interconversion rate, resulting in no clinically relevant difference in overall exposure to the two isomers. However, in monkeys, the in vivo elimination rate was higher than the R-/S-interconversion rate, resulting in 1.72- and 1.55-fold differences in R- versus S-isomer exposures. Monte Carlo simulation indicated that exposure to R- and S-enantiomers in humans should be comparable even if single isomers are administered. Thus, in humans, rapid isomeric interconversion of pomalidomide isomers results in comparable exposure to R- and S-enantiomers regardless of whether pomalidomide is administered as a single enantiomer or as a racemate, therefore justifying the clinical development of pomalidomide as a racemate.

Chiral Switch Drugs for Asthma and Allergies: True Benefit or Marketing Hype

Enantiomers are one of several possible molecular configurations present in a drug that has at least 1 chiral center. A drug containing 2 or more enatiomers is called a racemic mixture. Enatiomers are being developed from racemic mixtures as drugs in their own right often to extend patent protection of highly popular drugs. However, the therapeutic advantages of single enantiomer drugs developed for respiratory use such as levalbuterol, arformoterol, and levocetirizine over their racemate has been disappointing. In addition, single enantiomer drugs may be several fold more expensive than the racemic drug. New single enantiomer drugs, which are stable (no interconversion back to the racemate) and have fewer adverse effects and a more predictable pharmacodynamic or pharmacokinetic profile would confer a therapeutic advantage and thus would be beneficial for clinical use.

A comparison of heart rate changes associated with levalbuterol and racemic albuterol in pediatric cardiology patients

BACKGROUND

To our knowledge, no data exist regarding the effect of levalbuterol and racemic albuterol on heart rate in pediatric cardiology patients.

OBJECTIVE

To compare heart rate change in pediatric cardiology patients receiving levalbuterol and/or racemic albuterol. The secondary objective was to identify characteristics associated with heart rate changes observed with these drugs.

METHODS

A review of electronic medical records at a pediatric academic hospital was conducted to determine the equivalence of heart rate change in patients receiving levalbuterol or racemic albuterol. Patients receiving at least 3 doses of levalbuterol and/or racemic albuterol during the study period were included if they were younger than 18 years and had a diagnosis of congenital heart disease (CHD), cardiomyopathy, or supraventricular tachycardia. Patients were excluded if they received a β-blocker or continuous racemic albuterol or did not have documented pre- and postdose heart rates.

RESULTS

One hundred ninety-two patients were included. One hundred forty-two received racemic albuterol, 40 received levalbuterol, and 10 received both racemic albuterol and levalbuterol. The mean increase in heart rate for patients receiving racemic albuterol and levalbuterol was 6.8 beats/min and 6.2 beats/min, respectively (p = 0.01). In patients with CHD, the racemic albuterol group experienced a mean heart rate increase of 6.6 beats/min compared to 6.3 beats/min in the levalbuterol group (p = 0.01). Equivalence was also determined in patients without surgical intervention and patients receiving concomitant cardiac and respiratory medications. Equivalence was not established in other analyzed subgroups secondary to insufficient sample sizes.

CONCLUSIONS

Racemic albuterol and levalbuterol were associated with increased heart rate in pediatric cardiology patients. This increase was found to be equivalent.

Pharmacology and therapeutics of bronchodilators

Bronchodilators are central in the treatment of of airways disorders. They are the mainstay of the current management of chronic obstructive pulmonary disease (COPD) and are critical in the symptomatic management of asthma, although controversies around the use of these drugs remain. Bronchodilators work through their direct relaxation effect on airway smooth muscle cells. at present, three major classes of bronchodilators, β(2)-adrenoceptor (AR) agonists, muscarinic receptor antagonists, and xanthines are available and can be used individually or in combination. The use of the inhaled route is currently preferred to minimize systemic effects. Fast- and short-acting agents are best used for rescue of symptoms, whereas long-acting agents are best used for maintenance therapy. It has proven difficult to discover novel classes of bronchodilator drugs, although potential new targets are emerging. Consequently, the logical approach has been to improve the existing bronchodilators, although several novel broncholytic classes are under development. An important step in simplifying asthma and COPD management and improving adherence with prescribed therapy is to reduce the dose frequency to the minimum necessary to maintain disease control. Therefore, the incorporation of once-daily dose administration is an important strategy to improve adherence. Several once-daily β(2)-AR agonists or ultra-long-acting β(2)-AR-agonists (LABAs), such as indacaterol, olodaterol, and vilanterol, are already in the market or under development for the treatment of COPD and asthma, but current recommendations suggest the use of LABAs only in combination with an inhaled corticosteroid. In addition, some new potentially long-acting antimuscarinic agents, such as glycopyrronium bromide (NVA-237), aclidinium bromide, and umeclidinium bromide (GSK573719), are under development, as well as combinations of several classes of long-acting bronchodilator drugs, in an attempt to simplify treatment regimens as much as possible. This review will describe the pharmacology and therapeutics of old, new, and emerging classes of bronchodilator.

Levosalbutamol for chronic obstructive pulmonary disease: a treatment evaluation

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is an inflammatory disorder associated with considerable morbidity and mortality. β2-adrenoceptor agonists (β2-agonists) act by stimulating the β2-adrenoceptor present on smooth muscle and other cells in the airways, resulting in bronchodilatation. β2-agonists play a central role in the treatment of breathlessness in patients with COPD. Salbutamol is a chiral drug with (R)- and (S)- isomers. Almost all β2-agonists that are currently used are racemic mixtures of (R)- and (S)-salbutamol.

AREAS COVERED

(R)-salbutamol alone (Xenopex®, generically known as levosalbutamol) is now indicated for the treatment or prevention of bronchospasm with reversible obstructive airway disease. This evaluation demonstrates that (R)-salbutamol provides a beneficial β2-agonist effect at a cellular level and in experimental models of airways disease. Furthermore, we demonstrate that (S)-salbutamol opposes the desirable effects of (R)-salbutamol and can actually cause features of asthma and COPD in vitro and in experimental asthma.

EXPERT OPINION

Despite this strong body of preclinical experimental evidence, (R)-salbutamol has not shown consistent superiority over (S)- or racemic salbutamol in the treatment of patients with COPD.

Albuterol and levalbuterol use and spending in Medicare beneficiaries with chronic obstructive pulmonary disease

BACKGROUND

The evidence for the benefits of branded levalbuterol over generic albuterol in patients with chronic obstructive pulmonary disease (COPD) is inconclusive. However, there are significant cost differences between these products.

OBJECTIVES

This study examined use and spending on albuterol and levalbuterol in a nationally representative sample of Medicare beneficiaries with COPD enrolled in Part D in 2006. It also examined differences in patient characteristics and use of other COPD drugs among recipients of these 2 short-acting β-agonists.

METHODS

Data were obtained from the 5% Medicare files for 2005-2006 linked to the 2006 Medicare Part D files. The sample consisted of all fee-for-service beneficiaries with COPD enrolled in stand-alone Part D plans in 2006. Patient characteristics and other COPD medication use were compared across albuterol-only users, levalbuterol-only users, and users of both albuterol and levalbuterol. Multinomial logistic regressions were used to identify factors independently associated with levalbuterol use.

RESULTS

There were 5.5 times more albuterol users than levalbuterol users in 2006; however, mean annual spending on levalbuterol was 18.6 times higher per user in 2006 than spending on albuterol ($1876 vs $101 per user, respectively). Levalbuterol-only users were more likely to be older than albuterol-only users (mean age: 71.5 vs 68.7 years; P < 0.05), as well as sicker (mean prescription drug hierarchical condition category score: 1.72 vs 1.55; P < 0.05) and residing in the South (67.9% vs 41.6%; P < 0.05). Levalbuterol-only users were more likely to use nebulizer forms covered under Part B than inhaler forms covered under Part D (78.6% vs 26.8%, respectively; P < 0.05), whereas albuterol-only users were more likely to use inhaler forms covered under Part D than nebulizer forms covered under Part B (82.2% vs 33.0%, respectively; P < 0.05).

CONCLUSIONS

In this sample of Medicare beneficiaries with COPD enrolled in Part D, mean annual spending in 2006 was significantly higher for levalbuterol than for albuterol. The differences between levalbuterol and albuterol users in terms of patient characteristics, geographic region, and drug formulation/device type, coupled with the inconclusive evidence for efficacy differences in the literature, highlight the need for further comparative clinical and cost-effectiveness studies of these agents.

Albuterol enantiomer levels, lung function and QTc interval in patients with acute severe asthma and COPD in the emergency department

Background

This observational study was designed to investigate plasma levels of albuterol enantiomers among patients with acute severe asthma or COPD presenting to the emergency department, and the relationship with extra-pulmonary cardiac effects (QTc interval) and lung function. Recent reviews have raised concerns about the safety of using large doses of β₂-agonists, especially in patients with underlying cardiovascular comorbidity. It has been demonstrated that significant extrapulmonary effects can be observed in subjects given nebulised (R/S)-albuterol at a dose of as little as 6.5 mg.

Methods

Blood samples were collected and plasma/serum levels of (R)- and (S)-albuterol enantiomers were determined by LC-MS and LC-MS/MS assay. Extra-pulmonary effects measured at presentation included ECG measurements, serum potassium level and blood sugar level, which were collected from the hospital medical records.

Results

High plasma levels of both enantiomers were observed in some individuals, with median (range) concentrations of 8.2 (0.6-24.8) and 20.6 (0.5-57.3) ng/mL for (R)- and (S)- albuterol respectively among acute asthma subjects, and 2.1 (0.0-16.7) to 4.1 (0.0-36.1) ng/mL for (R)- and (S)- albuterol respectively among COPD subjects. Levels were not associated with an improvement in lung function or adverse cardiac effects (prolonged QTc interval).

Conclusions

High plasma concentrations of albuterol were observed in both asthma and COPD patients presenting to the emergency department. Extra-pulmonary cardiac adverse effects (prolonged QTC interval) were not associated with the plasma level of (R)- or (S)-albuterol when administered by inhaler in the emergency department setting. Long-term effect(s) of continuous high circulating albuterol enantiomer concentrations remain unknown, and further investigations are required.

(R)-salbutamol in the treatment of asthma and chronic obstructive airways disease

INTRODUCTION

Asthma and chronic obstructive pulmonary disease (COPD) are inflammatory disorders that have an increasing prevalence and associated morbidity and mortality. β(2)-adrenoceptor agonists (β(2)-agonists) act by stimulating the β(2)-adrenoceptor present on airway smooth muscle and other cells in the airway, resulting in bronchodilatation. β(2)-agonists are among the most commonly used drugs in the world and remain pivotal in the treatment of symptoms in patients with asthma and COPD. Salbutamol is a chiral drug with (R)- and (S)- isomers. Almost all β(2)-agonists that are used at present are racemic mixtures of (R)- and (S)-salbutamol.

AREAS COVERED

In this review the authors show that (R)-salbutamol alone (generically known as levosalbutamol) provides beneficial β(2)-agonist effects at a cellular level and in experimental models of airways disease. In addition the authors demonstrate that (S)-salbutamol opposes the desirable effects of (R)-salbutamol and can actually cause features of asthma and COPD in vitro and in experimental asthma.

EXPERT OPINION

Despite this strong body of experimental evidence, (R)-salbutamol has not shown consistent superiority over (S)- or racemic salbutamol in human asthma or COPD.

Efficacy of racemic albuterol versus levalbuterol used as a continuous nebulization for the treatment of acute asthma exacerbations: a randomized, double-blind, clinical trial

OBJECTIVE

To compare racemic albuterol (RAC) with levalbuterol (LEV) in continuous form for the treatment of acute pediatric asthma exacerbations in the emergency department.

STUDY DESIGN

Children between the ages of 6 and 17 inclusive were enrolled if they had a history of asthma, presented to the emergency department with an acute asthma exacerbation, and had an initial forced expiratory volume in 1 second (FEV1) <70% predicted. Patients were then randomized to receive either 7.5 mg of RAC or 3.75 mg of LEV over 1 hour, in addition to standard asthma therapies. Spirometry and asthma scoring were performed at the end of the first hour, and a second hour-long nebulization with the same drug was administered if deemed necessary. Spirometry and asthma scoring were again performed and the final disposition was recorded. As a second, optional part of the study, baseline serum albuterol levels were collected on some patients before treatment.

RESULTS

A total of 99 patients completed the study (44 RAC and 55 LEV). Baseline characteristics were similar except that the RAC group had a higher baseline asthma score. Children in the RAC group had a greater improvement in their FEV1 (p = .043) as well as in their asthma scores (p = .01) after 1 hour of continuous treatment compared to the LEV group. The greater improvement in asthma scores was maintained after the second hour of continuous therapy in the RAC group (p = .008) but not for FEV1 measurements (p = .57). There were no differences between groups for changes in heart rate, respiratory rate, oxygen saturation, or rates of admission.

CONCLUSIONS

At the doses used, RAC appears to be superior to LEV with respect to changes in FEV1 and asthma score. There was no significant difference between the drugs with respect to admission rates or side-effect profile.

Albuterol HFA for the management of obstructive airway disease

Albuterol (salbutamol outside the USA) is used to acutely relieve symptoms related to airway obstruction and prevent exercise-induced bronchospasm. Albuterol is most commonly administered by metered-dose inhaler (MDI). MDIs had used chlorofluorocarbon (CFC) propellants, but CFCs accumulate in the stratosphere and contribute to ozone catabolism. Loss of the 'ozone layer', which filters UVB rays, has public health concerns. Albuterol has been reformulated in MDIs using hydrofluoroalkane (HFA) propellants, which do not affect the ozone layer. Albuterol HFA MDIs deliver the same amount of drug per puff with similar particle size distributions as albuterol CFC MDIs, resulting in comparable bronchodilator efficacy of the two products. The highly favorable safety profile of albuterol has not been altered with reformulation. The propellant HFA-134a appears to be devoid of safety concerns.

Levalbuterol versus albuterol

Albuterol has been used for more than 40 years to treat acute asthma exacerbations as a racemic mixture of isomers: the active form, (R)-albuterol, or levalbuterol, and (S)-albuterol, classically considered inert. The single-isomer formulation, levalbuterol, has been synthesized recently and used therapeutically when the racemate is deemed less desirable. Basic investigations indicate that racemic albuterol and levalbuterol can produce effects that favor asthma remediation, including corticosteroid amplification and reduction of inflammatory mediators; in contrast, (S)-albuterol produces opposite effects. With inhalation of racemic albuterol, circulating (S)-albuterol persists 12 times longer than levalbuterol, suggesting potential for paradoxical effects observed clinically. Although mainly consistent with basic findings, clinical studies suggest no overwhelming superiority of levalbuterol over racemic albuterol; however, levalbuterol's effects may be greatest in moderate to severe asthma patients, especially with racemic albuterol overuse. Recent adoption of the hydrofluoroalkane formulation has narrowed the cost gap between levalbuterol and racemic albuterol metered-dose inhalers, but it remains for the nebulized formulations. Thus, physician selection of these drugs has remained dependent on experience, pharmaceutical knowledge, and established prescribing habits combined with cost factors, formulary structures, and availability, such that racemic albuterol is still used significantly compared with levalbuterol to treat acute asthma exacerbations.

High-dose continuous nebulized levalbuterol for pediatric status asthmaticus: a randomized trial

OBJECTIVE

To assess the use of high-dose continuous levalbuterol (LEV), the single active (R)-enantiomer of racemic albuterol (RAC), in the treatment of status asthmaticus.

STUDY DESIGN

Children age 6 to 18 years with severe asthma exacerbation were enrolled in this randomized, double-blind trial if they failed initial emergency department (ED) therapy with RAC and systemic steroids. Subjects received equipotent doses of RAC (20 mg/hour) or LEV (10 mg/hour) within a standardized inpatient protocol. Blood samples for measurements of albuterol enantiomer, potassium, and glucose levels were obtained from the first 40 subjects. The median time until discontinuation of continuous therapy was compared using the rank-sum test, and other outcomes were compared using general linear mixed models.

RESULTS

A total of 81 subjects (40 in the RAC group and 41 in the LEV group) were enrolled; the 2 groups were similar at baseline. Both groups tolerated continuous therapy with similar changes in heart rate and serum potassium and glucose levels but higher serum (S)-albuterol concentrations in the subjects treated with RAC. The median time for continuous therapy was similar in the RAC and LEV groups (18.3 hours vs 16.0 hours), as were the other clinical measures.

CONCLUSIONS

Substituting high-dose continuous LEV for RAC did not reduce the time on continuous therapy and had similar adverse effects in children who had failed initial treatment with RAC.

A cumulative dose study of levalbuterol and racemic albuterol administered by hydrofluoroalkane-134a metered-dose inhaler in asthmatic subjects

BACKGROUND

The short-acting beta(2)-agonists levalbuterol and racemic albuterol are available for administration through a hydrofluoroalkane-134a (HFA) metered-dose inhaler (MDI).

OBJECTIVE

This study compared the short-term safety and efficacy of cumulative doses of levalbuterol HFA MDI and racemic albuterol HFA MDI in asthmatic subjects.

METHODS

This was a randomized, modified-blind, active-controlled, multicenter, 2-way crossover study. Subjects (n = 49) were randomized to 16 cumulative doses (1x, 2x, 4x, 8x, and 16x) of levalbuterol (45 microg per dose) or racemic albuterol (90 microg per dose) administered over a 2-hour period. After a 7-day washout period, subjects were crossed over to the other treatment. After each dose, safety outcomes and pulmonary function were assessed.

RESULTS

Heart rate and (R)-albuterol exposure increased for both racemic albuterol HFA and levalbuterol HFA. For cumulative doses of 8x or greater, racemic albuterol HFA treatment had greater increases in mean heart rate than levalbuterol HFA (least-squares mean [+/- SD] difference at the 8x dose was 2.8 beats/min [95% CI, 0.3-5.3] and at the 16x dose was 3.5 beats/min [95% CI, 0.6-6.4]). (R)-albuterol plasma levels ranged from 10% to 18% higher after racemic albuterol HFA MDI dosing versus after levalbuterol HFA MDI. FEV(1) improvements were similar for both treatments. The relative potencies of the 2 therapies, based on FEV(1), were similar (ratio, 1.1 [90% CI, 0.9-1.2]; Finney method).

CONCLUSION

In this study single-day cumulative dosing of asthmatic subjects with levalbuterol HFA MDI or racemic albuterol HFA MDI resulted in similar improvements in FEV(1) and tolerability. Plasma (R)-albuterol levels and mean heart rate were less with levalbuterol HFA MDI.

Population pharmacodynamic model of bronchodilator response to inhaled albuterol in children and adults with asthma

BACKGROUND

Because interpatient variability in bronchodilation from inhaled albuterol is large and clinically important, we characterized the albuterol dose/response relationship by pharmacodynamic modeling and quantified variability.

METHODS

Eighty-one patients with asthma (24% African American [AA]; 8 to 65 years old; baseline FEV1, 40 to 80% of predicted) received 180 microg of albuterol from a metered-dose inhaler (MDI), and then 90 microg every 15 min until maximum improvement or 540 microg was administered; all then received 2.5 mg of nebulized albuterol. FEV1 was measured 15 min after each dose. The population cumulative dose/response data were fitted with a sigmoid maximum effect of albuterol (Emax) [maximum percentage of predicted FEV1 effect] model by nonlinear mixed-effects modeling. The influence of covariates on maximum percentage of predicted FEV1 reached after albuterol administration (Rmax) and cumulative dose of albuterol required to bring about 50% of maximum effect of albuterol (ED50) and differences between AA and white patients were explored.

RESULTS

ED50 was 141 microg, and Emax was 24.0%. Coefficients of variation for ED50 and Emax were 40% and 56%, respectively. Ethnicity was a statistically significant covariate (p < 0.05). AA and white patients reached 82.4% and 91.9% of predicted FEV1, respectively (p = 0.0004); and absolute improvement in percentage of predicted FEV1 was 16.6% in AA patients vs 26.7% in white patients (p < 0.0003). There were no baseline characteristic differences between AA and white patients. Nebulized albuterol increased FEV1 > or = 200 mL in 21% of participants. Heart rate and BP were unchanged from baseline after maximal albuterol doses.

CONCLUSIONS

Our model predicts that 180 microg of albuterol by MDI produces a 14.4% increase in percentage of predicted FEV1 over baseline (11.7% in AA patients, and 17.5% in white patients). Emax varies widely between asthmatic patients. AA patients are less responsive to maximal doses of inhaled albuterol than white patients.

Three generations of ongoing controversies concerning the use of short acting beta-agonist therapy in asthma: a review

An increase in asthma mortality in 1960s noted by British authors stirred a debate about the use of beta-adrenergic therapy that has persisted in the medical literature. The cause appears to be isoproterenol and fenoterol overuse. A second debate evolved around the possible deleterious, pro-inflammatory effects, of the albuterol distomer. Most clinical studies showed improved bronchodilatation, but limited benefits from using levalbuterol. Recently, genotyping has uncovered a single nucleotide polymorphism at codon 16 that appears to affect the long term response to both regular and as needed use of albuterol, calling for a new genotype based therapeutic approach in asthma.

An evaluation of levalbuterol HFA in the prevention of exercise-induced bronchospasm

Background

Exercise-induced bronchospasm (EIB) affects up to 90% of all patients with asthma.

Objective

This study evaluated the ability of levalbuterol hydrofluoroalkane (HFA) 90 μg (two actuations of 45 μg) administered via metered dose inhaler (MDI) to protect against EIB in mild-to-moderate asthmatics.

Methods

This was a randomized, double-blind, placebo-controlled, two-way cross-over study. Patients with asthma (n = 15) were ≥18 years, had a ≥6-month history of EIB, ≥70% baseline predicted forced expiratory volume in 1 second (FEV₁), and a 20% to 50% decrease in FEV₁ after treadmill exercise challenge using single-blind placebo MDI. Levalbuterol or placebo was self-administered 30 minutes before exercise. Treatment sequences were separated by a 3-to 7-day washout period. Spirometry was performed predose, 20 minutes postdose/pre-exercise, and 5, 10, 15, 30, and 60 minutes post-exercise. The primary endpoint was the maximum percent decrease in FEV₁ from baseline (postdose/pre-exercise). The percentage of protected (≤20% decrease in post-exercise FEV₁) patients was also assessed.

Results

Levalbuterol had significantly smaller maximum percent post-exercise decrease in FEV₁ compared with placebo (LS mean ± SE; −4.8% ± 2.8% versus −22.5% ± 2.8%, respectively). For levalbuterol, 14/15 (93.3%) patients had <20% decrease in post-exercise FEV₁ compared with 8/15 (53.3%) for placebo (p = 0.0143). Treatment was well tolerated.

Conclusion

Levalbuterol HFA MDI (90 μg) administered 30 minutes before exercise was significantly more effective than placebo in protecting against EIB after a single exercise challenge and was well tolerated.

Clinical Implications

Levalbuterol HFA MDI when administered before exercise was effective in protecting adults with asthma from EIB.

Effects of albuterol isomers on the contraction and Ca2+ signaling of small airways in mouse lung slices

The beta(2)-adrenergic agonist, albuterol, is used as a bronchodilator by patients with asthma and consists of a racemic mixture of (R)- and (S)-albuterol. However, the action of the individual enantiomers is poorly understood. Consequently, we investigated the effects of (R)-, (S)- and racemic-albuterol on airway smooth muscle cell (SMC) contraction and Ca(2+) signaling in mouse lung slices with phase-contrast and confocal microscopy. (R)-albuterol relaxed airways contracted with methacholine (MCh) in a dose-dependent manner. By contrast, (S)-albuterol had no effect on airways. (R)-albuterol had a greater relaxant effect than a double concentration of racemic albuterol. Because MCh-induced contraction of airway SMCs is mediated by Ca(2+) oscillations and an increase in Ca(2+) sensitivity, the effects of albuterol on these responses were examined. Both (R)- and racemic albuterol decreased the frequency of the MCh-induced Ca(2+) oscillations by a similar amount. However, (R)-albuterol was more effective than racemic albuterol in decreasing the Ca(2+) sensitivity of the airway SMCs in "model" lung slices with a clamped [Ca(2+)](i). In contrast, (S)-albuterol had no effect on the Ca(2+) oscillations or the Ca(2+) sensitivity. In conclusion, (R)-albuterol consistently induced a greater airway relaxation than racemic albuterol, and (S)-albuterol appears to be responsible for this reduced efficacy.

Levalbuterol for asthma: a better treatment?

The purpose of this review is to determine whether the proinflammatory actions identified in vitro for (S)-albuterol provide a clinically significant therapeutic advantage for levalbuterol over racemic albuterol. Clinical trials evaluating the bronchodilation in chronic and acute asthma provide conflicting evidence. Older trials suggested an advantage for levalbuterol; however, the newer trials have failed to confirm those advantages. Although (S)-albuterol produces increased bronchial hyperresponsiveness in vitro and in animal models, this has not been consistently confirmed in clinical trials; however, the heterogeneity of the trials precludes definitive conclusions. Current clinical trials do not provide evidence of a substantial advantage of levalbuterol over racemic albuterol although the data are insufficient to determine whether subsets of the patient population might benefit from single isomer therapy.

Novel medications for asthma: a look at the future

The principal components of the asthmatic response are airways hyper-responsiveness, persistent inflammation and mucus hypersecretion. Although these components are inter-related, any of these can predominate at different times and for different patients and each requires a different approach to therapy. As a result of the inflammation and epithelial damage, there can be abnormal repair mechanisms leading to fixed airflow obstruction that has been termed 'airways remodeling'. Although there are a number of highly effective therapeutic agents used to treat asthma today, novel therapies are being designed to more specifically and safely target these different components and better meet the needs of patients with asthma.

Evidence based review on levosalbutamol

Salbutamol, the most commonly used bronchodilator, is a chiral drug with R (levosalbutamol) and S-isomers (also known as enantiomer). The commonly used formulation is a racemic mixture that contains equal amounts of both R and S isomers. Levosalbutamol is the therapeutically active isomer and has all the beta 2 agonist activity. Until recently S-salbutamol was considered inert filler in the racemic mixture but animal as well as human studies have shown that S-salbutamol is not inert rather it may have some deleterious effects. Enantioselective metabolism of salbutamol leads to higher and sustained plasma levels of S-salbutamol with repeated dosing. There has been concern that chronic use of racemic salbutamol may lead to loss of effectiveness and clinical deterioration. Formulation of salbutamol containing only R- isomer (levosalbutamol) has been available in international market since last few years. Clinical trials in acute as well as chronic asthma in adults as well as children have shown that it has therapeutic advantage over racemic salbutamol and also is more cost effective. But, large multicenter trials are needed to prove its therapeutic superiority and cost-effectiveness in long term.

Comparison of bronchodilator responses of levosalbutamol and salbutamol given via a pressurized metered dose inhaler: a randomized, double blind, single-dose, crossover study

BACKGROUND

Salbutamol, the most widely used short-acting beta(2)-agonist, consists of a racemic mixture of equal amounts of two enantiomers, (R)-salbutamol and (S)-salbutamol. The bronchodilator effects of salbutamol are attributed entirely to (R)-salbutamol (levosalbutamol), while (S)-salbutamol has been shown to possess bronchospastic and pro-inflammatory effects both in vitro and in vivo studies. Levosalbutamol, the (R)-enantiomer of salbutamol is currently available only in a liquid formulation for use via a nebulizer. Recently, levosalbutamol to be administered via a pressurized metered dose inhaler (pMDI) has been developed.

AIMS

To compare the time-dependent bronchodilator responses of single doses of 100mcg levosalbutamol and 200 mcg racemic salbutamol administered via a pMDI in subjects with stable mild-to-moderate bronchial asthma over a period of 6h.

METHODS

Single doses of 100 mcg levosalbutamol, 200 mcg salbutamol and placebo were administered with a pMDI in 30 stable asthmatic subjects in a randomized, double-blind, placebo-controlled, three-way cross over study. Forced expiratory volume in 1s (FEV(1)) and forced vital capacity (FVC) were measured at baseline, and over 6h post-study drug administration.

RESULTS

Levosalbutamol and salbutamol produced significantly better bronchodilator responses than placebo. Both the drugs showed equivalent time-dependent bronchodilator responses as measured by area under curve for percent change in FEV(1) and FVC over 6h. The time to onset of action, mean maximum bronchodilator response and duration of bronchodilator response were similar between levosalbutamol and salbutamol.

CONCLUSION

A single dose of 100 mcg levosalbutamol administered by a pMDI produced a similar bronchodilator response as salbutamol when measured over 6h in subjects with stable, mild-to-moderate bronchial asthma.

(R)-albuterol for asthma: pro [a.k.a. (S)-albuterol for asthma: con]

Is there scientific evidence to support the replacement of the beta-agonist racemic albuterol with levalbuterol--that is, (R)-albuterol? The argument presented further refines the question as "Do we wish to continue to treat asthma with a mixture of albuterol, of which half is an agent with no known benefit--that is, (S)-albuterol--and which may exacerbate the disease?"

Levosalbutamol in the treatment of asthma

With the exception of levosalbutamol, all of the beta2-agonists that are currently in use are racemic mixtures that are composed in equal amounts of (R)- and (S)-enantiomers. Clinical and mechanistic studies have demonstrated that (R)-salbutamol alone provides the beta2-agonist activity that is needed for the relief of bronchoconstriction, as well as the beta2-adrenergically mediated side effects. (S)-Salbutamol, on the other hand, has minimal binding affinity for the beta2-receptor, indicating that its effects are likely to be mediated through another site. Furthermore, there is evidence that (S)-salbutamol opposes the desirable effects of (R)-salbutamol in the racemic mixture and contributes to the development of characteristic features of asthma, such as airway obstruction, bronchial hyperresponsiveness and airway inflammation. Evidence from clinical studies shows delayed recovery from exacerbation of asthma by patients who are exposed to high concentrations of (S)-salbutamol.

A comparison of levalbuterol with racemic albuterol in the treatment of acute severe asthma exacerbations in adults

This multicenter, randomized, double-blind trial compared nebulized levalbuterol (Lev) and racemic albuterol (Rac) in the treatment of acute asthma.

METHODS

Adults with acute asthma exacerbations (FEV(1) 20%-55% predicted) received prednisone and either Lev (1.25 mg, n = 315) or Rac (2.5 mg, n = 312). Nebulized treatments were administered every 20 minutes in the first hour, then every 40 minutes for 3 additional doses, then as necessary for up to 24 hours. The primary end point was time to meet discharge criteria. Secondary end points included changes in lung function and hospitalization rates. A subset of 160 patients had plasma (S)-albuterol concentrations determined at study entry.

RESULTS

Time to meet discharge criteria did not differ between the 2 treatments. FEV(1) improvement was greater following Lev compared with Rac, both after dose 1 and cumulatively over the entire treatment period (dose 1 in intent to treat [ITT] group: Lev 0.50 +/- 0.43 L, Rac 0.43 +/- 0.37 L; P = .02), particularly among the 60% of patients not on recent steroid therapy (dose 1: Lev 0.58 +/- 0.47 L, Rac 0.44 +/- 0.37 L; P < .01), and patients whose entry (S)-albuterol concentrations were in the highest quartile of those measured. A small and similar proportion of Lev-treated (7.0%) and Rac-treated (9.3%) patients required hospitalization (P = .28). Among patients not on steroids, fewer Lev- than Rac-treated patients required admission (3.8% vs 9.3%, P = .03), as was also the case for patients with high plasma (S)-albuterol concentrations. Asthma relapses (5% in 30 days) were lower than in previous reports and did not differ between groups.

CONCLUSIONS

This study suggests that early, regular nebulized beta(2)-agonist and systemic corticosteroid therapy may reduce hospitalization and relapse rates in patients with acute severe asthma. Lev was well tolerated and compared favorably with Rac in improving airway function, particularly in those who were not on inhaled or oral corticosteroids and in those who had high plasma (S)-albuterol concentrations at presentation.

Clinical efficacy of racemic albuterol versus levalbuterol for the treatment of acute pediatric asthma

STUDY OBJECTIVE

An efficacy treatment study is conducted comparing levalbuterol to racemic albuterol for acute pediatric asthma in the emergency department (ED).

METHODS

This was a prospective, double-blind, randomized, controlled study involving 129 children (2 to 14 years), presenting to a pediatric ED with an acute moderate or severe asthma exacerbation. Children were treated using a standard ED asthma pathway. Primary outcomes were changes from baseline in clinical asthma score and the percentage of predicted forced expiratory volume in 1 second after the first, third, and fifth treatment. Secondary outcomes included number of treatments, length of ED care, rate of hospitalization, and changes in pulse rate, respiratory rate, and oxygen saturation. Occurrence of adverse events was recorded.

RESULTS

Sixty-four children in the racemic albuterol and 65 children in the levalbuterol group completed the study. There were no differences between groups in primary outcomes, secondary outcomes, or adverse events.

CONCLUSION

There was no difference in clinical improvement in children with acute moderate to severe asthma exacerbations treated with either racemic albuterol or levalbuterol.

Evaluation of the safety and efficacy of levalbuterol in 2-5-year-old patients with asthma

The purpose of this study was to evaluate the safety and efficacy of single-isomer (R)-albuterol (levalbuterol, LEV) in children aged 2-5 years. Children aged 2-5 years (n = 211) participated in this multicenter, randomized, double-blind study of 21 days of t.i.d. LEV (0.31 mg or 0.63 mg without regard to weight), racemic albuterol (RAC, 1.25 mg for children <33 pounds (lb); 2.5 mg for children >/=33 lb), or placebo (PBO). Endpoints included adverse-event (AE) reporting, safety parameters, peak expiratory flow (PEF), the Pediatric Asthma Questionnaire(c) (PAQ), and the Pediatric Asthma Caregiver's Quality of Life Questionnaire (PACQLQ). Baseline disease severity was generally mild in all groups, as defined by PAQ scores that ranged from 6.3-7.3 on a scale of 0-27 and 1.5 days/week of uncontrolled asthma. After treatment, the PAQ decreased in all groups (P = NS). In the subset of subjects able to perform PEF (51.7%), all active treatments improved in-clinic PEF after the first dose (mean +/- SD: PBO, 1.4 +/- 20.8; LEV 0.31 mg, 12.4 +/- 12; LEV 0.63 mg, 16.7 +/- 15.4; RAC, 18.0 +/- 16.5 l/min; P < 0.01). PACQLQ measurements improved more than the minimally important difference only in the LEV-treated groups, and were significant in children <33 lb (P < 0.05). Asthma exacerbations occurred primarily in children >/=33 lb, and one serious asthma exacerbation occurred in the 2.5-mg RAC group. RAC and LEV 0.63 mg, but not LEV 0.31 mg or placebo, led to significant increases in ventricular heart rate. In this study of levalbuterol in children aged 2-5 years with asthma, LEV was generally well-tolerated, and in children able to perform PEF, led to significant bronchodilation compared with placebo.

Automatic replacement of albuterol nebulizer therapy by metered-dose inhaler and valved holding chamber

PURPOSE

Evidence supporting the delivery of bronchodilators with a metered-dose inhaler and a valved holding chamber (MDI+VHC) in place of a small-volume nebulizer (SVN) is discussed, and the steps taken to accomplish such a conversion program at one institution are described.

SUMMARY

Double-blind, randomized studies in patients with acute exacerbations of asthma have demonstrated that higher doses of albuterol delivered by MDI+VHC (4-10 puffs per dose) are as effective as 2.5 mg of albuterol sulfate delivered by SVN. Three double-blind studies support the conclusion that the two methods are equivalent with respect to both efficacy and adverse effects in patients with chronic obstructive pulmonary disease. MDI+VHC offers practical advantages over SVN, including the capacity for home use by the patient, portability, less setup time, and no need for daily disinfection. Pharmacists and respiratory therapists obtained approval through the pharmacy and therapeutics committee for respiratory therapists to convert orders for bronchodilators delivered by SVN to administration by MDI+VHC. The conversion policy allows physicians to override it, but none have exercised this option. On intensive care units (ICUs), the policy resulted in a 53% increase in the use of MDI+VHC during the six-month period after it went into effect. Respiratory therapists have been less thorough in implementing the policy for non-ICU patients.

CONCLUSION

Delivery of bronchodilators by MDI+VHC is as effective as delivery by SVN but offers several advantages. A policy to switch patients from SVN to MDI+VHC for bronchodilator administration met with limited success.

Beta2-agonist eutomers: a rational option for the treatment of asthma?

Beta2-adrenoceptor agonists (beta2-agonists) such as albuterol (salbutamol) and terbutaline and their long-acting analogs salmeterol and formoterol are widely used as bronchodilators in the treatment of asthma. They are chiral drugs historically marketed as racemic mixtures of an active (eutomer) and essentially inactive (distomer) stereoisomer. Despite their obvious therapeutic value and widespread use, beta2-agonists have been implicated, somewhat controversially, in causing an increase in asthma mortality and a deterioration of asthma control by a mechanism that remains elusive. Inherent toxicity of the distomers has been widely touted as an explanation and has given rise to pressure for the replacement of the racemates with pure eutomer formulations (the so-called chiral or racemic switch). This has culminated in the recent introduction into clinical practice of the single active stereoisomer of albuterol (levalbuterol) and the promise of other pure beta2-agonist eutomer formulations to follow. This article examines the evidence on which these chiral switches are based. Clinical studies designed to reveal negative effects of beta2-agonists have searched for reductions in lung function, increases in airway responsiveness to bronchoconstrictor mediators and worsening of asthma control. Crossover studies administering the pure stereoisomers and racemate of albuterol have not shown a clear superiority of the pure eutomer formulation over the racemate in terms of either bronchial hyperresponsiveness, tachyphylaxis to bronchoprotective effects or improvements in lung function. Clinical toxicity of beta2-agonist distomers on any aspect of asthmatic lung function has also not been demonstrated in the relatively short-term inhalational studies (single dose or repeated dose studies <1 week) that have been carried out. In animal studies, the administration of beta2-agonist racemates and distomers has been shown to enhance bronchial hyperresponsiveness but only in ovalbumin-sensitized animals where the relevance to humans is questionable. The pharmacokinetics and metabolism of beta(2)-agonist stereoisomers appear to be essentially similar whether administered as single stereoisomers or as racemates. Levalbuterol may be slightly more potent than an equivalent dose given as racemate, but there is some evidence that it forms a small amount of the distomer in vivo which detracts somewhat from its purported benefits over use of the racemate. Whilst there remains a clear need for studies of longer duration with sensitive clinical endpoints to evaluate the benefits of beta2-agonist eutomers and to investigate distomer toxicity, the chiral switch for beta2-agonists in general, and for albuterol in particular, does not appear to be justified on the basis of the evidence available to date.

Past, present and future--beta2-adrenoceptor agonists in asthma management

The beta-adrenoceptor agonists (beta-agonists) have been used to relieve bronchoconstriction for at least 5000 years. beta-agonists are based on adrenaline and early forms, such as isoprenaline, Lacked bronchial selectivity and had unpleasant side effects. Modern beta-agonists are more selective for the beta2-adrenoceptors (beta2-receptors) located in bronchial smooth muscle and have less cardiotoxicity. Traditional beta2-adrenoceptor agonists (beta2-agonists), such as salbutamol, terbutaline and fenoterol, were characterised by a rapid onset but relatively short duration of action. While valuable as reliever medication, their short duration gave inadequate night-time relief and limited protection from exercise-induced bronchoconstriction. beta2-agonists with longer durations of action, formoterol and salmeterol, were subsequently discovered or developed. When combined with inhaled corticosteroids they improved lung function, and reduced symptoms and exacerbations more than an increased dose of corticosteroids. However, tolerance to the bronchprotective effects of long-acting beta2-agonists and cross-tolerance to the bronchodilator effects of short-acting beta2-agonists is apparent despite use of inhaled corticosteroids. The role of beta2-receptor polymorphisms in the development of tolerance has yet to be fully determined. Formoterol is unique in having both a long-lasting bronchodilator effect (> 12 h) and a fast onset of action (1-3min from inhalation), making it effective both as maintenance and reliever medication. The recent change in classification from short- and long-acting beta2-agonists to rapid-acting and/or long-acting agents reflects the ongoing evolution of beta2-agonist therapy.

What is new with the beta2-agonists: issues in the management of asthma

OBJECTIVE

To review the more recent literature addressing the issue of whether beta2-agonists can worsen asthma and/or increase the risk of severe exacerbations and death from asthma.

DATA SOURCES

PubMed was searched (2001-December 2004), along with the Food and Drug Administration and Cochrane Library Web sites. In addition, the bibliographies of recent reviews of the subject were assessed.

STUDY SELECTION AND DATA EXTRACTION

Randomized clinical trials, retrospective and prospective cohort studies, and meta-analyses published in the past 3 years were reviewed. Studies assessing the potential for beta2-agonists to worsen outcomes in asthma as well as long-term studies assessing asthma outcomes that included an arm with regular administration of short- or long-acting inhaled beta2-agonists (LABAs) were selected. Worsening asthma was defined as a decline in lung function, an increase in bronchial hyperresponsiveness, exacerbations, or death. Studies older than 3 years selected from the bibliographies of the primary articles that addressed background perspective were also included where appropriate.

DATA SYNTHESIS

The studies fell into 3 primary categories with some overlap: those assessing toxicity of the S-enantiomer of albuterol, those evaluating the risk of specific genotypes regarding worsening asthma, and those assessing asthma outcomes with LABA therapy.

CONCLUSIONS

The current data on the use of beta2-agonists continue to support the national and international guidelines for the treatment of asthma. That is, short-acting inhaled beta2-agonists should only be used as needed for symptoms and prevention of exercise-induced bronchospasm, and LABAs should only be used regularly as adjunctive therapy with inhaled corticosteroids in patients whose asthma is not controlled with low to medium doses of the inhaled corticosteroid.

New strategies in the treatment and prevention of allergic diseases

Allergic diseases (AD) are more prevalent today than 30 years ago but over the same period, few novel efficacious drugs have been discovered to treat, control or even cure these disorders. Topical or systemic glucocorticosteroids combined with symptom-relieving medications, such as beta 2 -adrenoceptor agonists, leukotriene inhibitors or antihistamines, are still the mainstay of antiallergic treatment. Modified glucocorticosteroids with less adverse effects, better bronchodilators and new selective mediator inhibitors may improve symptom control in the future. Only specific immunotherapy has shown potential for long-lasting disease-modifying effects. Immunomodulation is a therapeutic goal, aiming to modify the dominant helper T cell Type 2 inflammation to a helper T cell Type 1 response using modified allergens, mycobacteria or CpG oligodeoxynucleotides. Humanised monoclonal anti-IgE antibodies are an exciting new immunomodulatory medication that are expected to reach the clinical practice and have recently been licensed in Australia and the US. Advances in molecular, cellular and genetic research of the immunopathophysiology of AD have led to the development of new antagonists for cytokines, chemokines, receptors, second messengers and transcription factors that may become available for clinical use in the next 10 years. Specific diets supplemented with antioxidants or probiotics need further study but offer promise as safe and cheap preventative medicine. The strong genetic component of AD and the Human Genome Project have opened a new field of research, and modification or replacement of target genes has a curative potential with exciting new therapeutic developments in the years ahead.

The effect of formoterol over 24 h in patients with asthma: the role of enantiomers

The single-dose effect of formoterol racemate and enantiomers on bronchodilatation up to 24 h was determined. Forty-six reversible asthmatic patients were randomised to this double blind, crossover study. Formoterol was inhaled by nebulizer (HaloLite); 4.5 and 36 microg of the racemate (rac-formoterol), 2.25 and 18 microg of (R;R)-formoterol, 18 mirog of (S;S)-formoterol, or placebo. Airway and systemic effects were assessed by serial measurements of forced expiratory volume during the first second, FEV1 (24 h), and heart rate (4 h). Rac- and (R;R)-formoterol significantly and dose-dependently increased FEV1 with similar mean maximal effect. (S;S)-formoterol was without significant effects on FEV1 and heart rate. (R;R)- and rac-formoterol were still effective 22-24 h after single high doses, but this was associated with some systemic side effect (increased heart rate) initially. Average 22-24 h FEV1 was 8% (rac-formoterol 36 microg) and 11% ((R;R)-formoterol 18 microg) over placebo, respectively. No significant differences in effects were observed between rac- and (R;R)-formoterol. Thus, the single dose bronchodilatating effect of formoterol resides in (R;R)-formoterol. This study does not indicate a clinically important advantage of (R;R)-formoterol as acute bronchodilator compared to the racemate.

Clinically relevant concentrations of beta2-adrenergic agonists stimulate maximal cyclic adenosine monophosphate-dependent airspace fluid clearance and decrease pulmonary edema in experimental acid-induced lung injury

OBJECTIVE

To determine whether clinically relevant airspace concentrations of beta2-adrenergic agonists stimulated maximal alveolar fluid clearance rates and to determine whether beta2 agonist therapy decreased pulmonary edema in experimental acute lung injury.

DESIGN

Prospective randomized laboratory investigation.

SETTING

University-affiliated laboratory.

SUBJECTS

Sprague Dawley rats.

INTERVENTIONS

Dibutyryl cyclic adenosine monophosphate (cAMP), salmeterol, albuterol, and isoproterenol in normal rat lung. Salmeterol in a rat model of acid-induced lung injury.

MEASUREMENTS AND MAIN RESULTS

Basal alveolar fluid clearance was 7.6 +/- 2.2 %/hr. Maximal cAMP-dependent alveolar fluid clearance rate was 32.9 +/- 10.9 %/hr (p <.05). Racemic albuterol 10(-5) M, salmeterol 10(-6) M, and isoproterenol 10(-6) M each stimulated alveolar fluid clearance to a level comparable to maximal cAMP-dependent alveolar fluid clearance. Compared with basal rates, alveolar fluid clearance was increased by both racemic albuterol 10(-6) M (14.5 +/- 3.0%, p <.05) and R-enantiomer 10(-6) M (15.0 +/- 4.6%, p <.05), but there was no difference between the two groups. Intra-alveolar salmeterol 10 (-6) M attenuated the degree of pulmonary edema following acid-induced lung injury. Extravascular lung water increased to only 180 +/- 30 microL with salmeterol treatment, compared with 296 +/- 65 microL in saline-treated rats 4 hrs after acid injury (p <.05). This decrease in lung water was accompanied by a 2.4-fold increase in the rate of alveolar fluid clearance at 4 hrs in the salmeterol-treated group. Lung endothelial permeability, expressed as extravascular plasma equivalents, was reduced to 64 +/- 9 microL with salmeterol compared with 119 +/- 51 microL in saline-treated rats 4 hrs after acid injury (p <.05).

CONCLUSIONS

Clinically relevant airspace concentrations of beta2-adrenergic agonists a) stimulate maximal cAMP-dependent airspace fluid clearance in normal lungs and b) reduce pulmonary edema in acid aspiration-induced lung injury by increasing alveolar fluid clearance and decreasing endothelial permeability. Clinical studies are required to determine whether beta2-adrenergic agonists improve outcome in patients with acute lung injury.

(S)-Albuterol activates pro-constrictory and pro-inflammatory pathways in human bronchial smooth muscle cells

BACKGROUND

Pro-constrictory and proinflammatory properties of (S)-albuterol have been widely reported both under in vivo and in vitro conditions. However, underlying mechanisms are unclear.

OBJECTIVE

We examined and compared the cellular effects of albuterol enantiomers on key intracellular molecules involved in constrictory and inflammatory pathways in human bronchial smooth muscle cells (hBSMCs).

METHODS

Primary hBSMCs were grown in culture and treated with various concentrations of albuterol enantiomers for various periods. Methacholine was used to stimulate cells. The expression and activity of Gs and Gi proteins, the intracellular free calcium concentration ([Ca2+]i), the activity of phosphatidylinositol 3'-OH-kinase (PI3) kinase, and the transcriptional nuclear factor kappaB (NF-kappaB) level were examined.

RESULTS

There was a significant increase in the expression and activity of Gialpha-1 protein and a decrease in the expression of Gs protein in hBSMCs after 8 hours of treatment with (S)-albuterol. These effects of (S)-albuterol were observed in a dose-dependent manner. Nonreceptor-mediated activation of adenylate cyclase by forskolin was attenuated with (S)-albuterol. Treatment of the cells for 24 hours with (S)-albuterol significantly increased [Ca2+]i on stimulation with methacholine. Interestingly, the effect of (R)-albuterol was opposite to that of (S)-albuterol. The effect of the racemic albuterol in some cases was similar to that of (S)-albuterol. (S)-Albuterol significantly activated both PI3 kinase and NF-kappaB in hBSMCs.

CONCLUSION

These studies demonstrated an (S)-albuterol-induced increase in the expression and activity of pro-constrictory pathways involving Gialpha-1 protein and [Ca2+]i and a decrease in the activity of the bronchodilatory pathway involving Gs proteins in hBSNMCs. Additionally, (S)-albuterol activated proinflammatory pathways involving PI3 kinase and NF-kappaB. Because (S)-albuterol metabolizes at least 10-fold slower than (R)-albuterol and has a longer elimination half-life, these cellular effects of (S)-albuterol might explain the detrimental effect seen with chronic administration of racemic albuterol in the treatment of airway diseases, such as bronchial asthma.

Three-dimensional pharmacology, a subject ranging from ignorance to overstatements

Stereoselectivity has been known to play a role in drug action for 100 years or more. Nevertheless, chiral drugs have been developed and used as racemates, neglecting the fact that they comprise mixtures of two or more compounds which may have quite different pharmacological properties. A very limited access to pure enantiomers in the past has been responsible for this unsatisfactory state of affairs. During the last 20 years, significant achievements have made it possible to perform stereoselective synthesis and analysis. Today, novel chiral drugs are as a rule developed as single enantiomers. Yet, studies of old racaemic drugs are still designed, performed and published without mention of the fact that two or more compounds are involved. In recent years, a number of old racaemic drugs have been re-evaluated and re-introduced into the clinical area as the pure, active enantiomer (the eutomer). While in principle correct, the clinical benefit of this shift from a well established racaemate to a pure enantiomer often seems to be limited and sometimes exaggerated. Racaemic drugs with a deleterious enantiomer that does not contribute to the therapeutic effect (the distomer), may have been sorted out in the safety evaluation process. However, in the future any pharmacological study of racaemic drugs must include the pure enantiomers. This will generate new, valuable information on stereoselectivity in drug action and interaction.

Comparison of racemic albuterol and levalbuterol for treatment of acute asthma

OBJECTIVE

To determine whether levalbuterol resulted in fewer hospital admissions than racemic albuterol when used for treatment of acute asthma. Study design A randomized, double-blind, controlled trial was conducted in the emergency department (ED) and inpatient asthma care unit of an urban tertiary children's hospital. Children age 1 to 18 years (n=482) provided a total of 547 enrollments. Patients received a nebulized solution of either 2.5 mg racemic albuterol or 1.25 mg levalbuterol every 20 minutes (maximum six doses). Patients admitted to the asthma care unit were treated in a standardized fashion by using the same blinded drug assigned in the ED. Hospitalization rate was the primary outcome.

RESULTS

Hospitalization rate was significantly lower in the levalbuterol group (36%) than in the racemic albuterol group (45 %, P=.02). The adjusted relative risk of admission in the racemic group compared with the levalbuterol group was 1.25 (95% confidence interval, 1.01-1.57). Hospital length of stay was not significantly shorter in the levalbuterol group (levalbuterol, 44.9 hours; racemic albuterol, 50.3 hours; P=.63). No significant adverse events occurred in either group.

CONCLUSIONS

Substituting levalbuterol for racemic albuterol in the ED management of acute asthma significantly reduced the number of hospitalizations.