Levalbuterol compared with racemic albuterol in the treatment of acute asthma: results of a pilot study

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.

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.

Anti-inflammatory effects of levalbuterol-induced 11β-hydroxysteroid dehydrogenase type 1 activity in airway epithelial cells

Airway epithelial NF-κB activation is observed in asthmatic subjects and is a cause of airway inflammation in mouse models of allergic asthma. Combination therapy with inhaled short-acting β2-agonists and corticosteroids significantly improves lung function and reduces inflammation in asthmatic subjects. Corticosteroids operate through a number of mechanisms to potently inhibit NF-κB activity. Since β2-agonists can induce expression of 11β-HSD1, which converts inactive 11-keto corticosteroids into active 11-hydroxy corticosteroids, thereby potentiating the effects of endogenous glucocorticoids, we examined whether this mechanism is involved in the inhibition of NF-κB activation induced by the β-agonist albuterol in airway epithelial cells. Treatment of transformed murine Club cells (MTCC) with (R)-albuterol (levalbuterol), but not with (S)- or a mixture of (R + S)- (racemic) albuterol, augmented mRNA expression of 11β-HSD1. MTCC were stably transfected with luciferase (luc) reporter constructs under transcriptional regulation by NF-κB (NF-κB/luc) or glucocorticoid response element (GRE/luc) consensus motifs. Stimulation of NF-κB/luc MTCC with lipopolysaccharide (LPS) or tumor necrosis factor-α (TNFα) induced luc activity, which was inhibited by pretreatment with (R)-, but not (S)- or racemic albuterol. Furthermore, pretreatment of GRE/luc MTCC with (R)-, but not with (S)- or racemic albuterol, augmented 11-keto corticosteroid (cortisone) induced luc activity, which was diminished by the 11β-HSD inhibitor glycyrrhetinic acid (18β-GA), indicating that there was a conversion of inactive 11-keto to active 11-hydroxy corticosteroids. LPS- and TNFα-induced NF-κB/luc activity was diminished in MTCC cells treated with a combination of cortisone and (R)-albuterol, an effect that was inhibited by 18β-GA. Finally, pretreatment of MTCC cells with the combination of cortisone and (R)-albuterol diminished LPS- and TNFα-induced pro-inflammatory cytokine production to an extent similar to that of dexamethasone. These results demonstrate that levalbuterol augments expression of 11β-HSD1 in airway epithelial cells, reducing LPS-induced NF-κB transcriptional activity and pro-inflammatory cytokine production through the conversion of inactive 11-keto corticosteroids into the active 11-hydroxy form in this cell type.

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.

(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.

Detrimental effects of albuterol on airway responsiveness requires airway inflammation and is independent of β-receptor affinity in murine models of asthma

BACKGROUND

Inhaled short acting β2-agonists (SABA), e.g. albuterol, are used for quick reversal of bronchoconstriction in asthmatics. While SABA are not recommended for maintenance therapy, it is not uncommon to find patients who frequently use SABA over a long period of time and there is a suspicion that long term exposure to SABA could be detrimental to lung function. To test this hypothesis we studied the effect of long-term inhaled albuterol stereoisomers on immediate allergic response (IAR) and airway hyperresponsiveness (AHR) in mouse models of asthma.

METHODS

Balb/C mice were sensitized and challenged with ovalbumin (OVA) and then we studied the IAR to inhaled allergen and the AHR to inhaled methacholine. The mice were pretreated with nebulizations of either racemic (RS)-albuterol or the single isomers (S)- and (R)-albuterol twice daily over 7 days prior to harvest.

RESULTS

We found that all forms of albuterol produced a significant increase of IAR measured as respiratory elastance. Similarly, we found that AHR was elevated by albuterol. At the same time a mouse strain that is intrinsically hyperresponsive (A/J mouse) was not affected by the albuterol isomers nor was AHR induced by epithelial disruption with Poly-L-lysine affected by albuterol.

CONCLUSIONS

We conclude that long term inhalation treatment with either isomer of albuterol is capable of precipitating IAR and AHR in allergically inflamed airways but not in intrinsically hyperresponsive mice or immunologically naïve mice. Because (S)-albuterol, which lacks affinity for the β2-receptor, did not differ from (R)-albuterol, we speculate that isomer-independent properties of the albuterol molecule, other than β2-agonism, are responsible for the effect on AHR.

Levosalbutamol vs racemic salbutamol in the treatment of acute exacerbation of asthma

OBJECTIVE

To compare efficacy and tolerability of levosalbutamol (Group 1) and racemic salbutamol (Group 2) for the treatment of acute exacerbation of asthma in children age 5 to 18 yr.

METHODS

A randomized double blind clinical study involving 60 children was undertaken between October' 06 to December' 07.

RESULTS

The following baseline clinical characteristic were recorded initially and after giving 3 nebulizations at 20 min intervals in the Ist hour of presentation viz respiratory rate (RR), heart rate (HR), oxygen saturation in room air SPO2, PEFR (peak expiratory flow rate), serum K+ level and asthma score. In Group 1 patients (levosalbutamol), there was significant increment in SPO2 and PEFR (P<0.05) values with decrease in tachypnea and asthma score while no significant difference was found in pre and post treatment HR & Serum K+ levels. In Group 2 patients although there was clinical improvement in terms of SPO2, PEFR, RR and asthma score, it resulted in significant tachycardia and decrease in K+ levels.

CONCLUSION

Levosalbutamol appears to be more efficacious than racemic salbutamol in terms of improvement in PEFR, SPO2 and asthma score while deleterious effects of tachycardia and fall in serum K+ were seen with racemic salbutamol.

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.

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.

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.

Comparison of the dose response to levalbuterol with and without pretreatment with S-albuterol after methacholine-induced bronchoconstriction

STUDY OBJECTIVE

To determine the effect of S-albuterol on the dose response to levalbuterol in patients with moderate bronchoconstriction induced by a methacholine challenge.

DESIGN

Prospective, randomized, double-blind, placebo-controlled, crossover study.

SETTING

University-affiliated clinical trial center.

PATIENTS

Twenty-two adults with mild, stable asthma.

INTERVENTION

At the screening visit, patients were switched from their beta2-agonist to ipratropium bromide for use as an as-needed rescue therapy. At the baseline visit 2-6 days later, the provocative concentration of methacholine to induce a 30% decrease in forced expiratory volume in 1 second (FEV(1) PC(30)) was determined, followed by a nebulized racemic albuterol dose-response study with three doses of albuterol, to familiarize patients with the procedures. At visits 2 and 3, patients were randomly assigned to receive nebulized normal saline placebo or S-albuterol 5 mg before the methacholine challenge and were administered three escalating doses of levalbuterol after the challenge.

MEASUREMENTS AND MAIN RESULTS

Area under the curve for FEV(1) over 40 minutes (AUC(0-40)) after administration of levalbuterol was the primary outcome, with slope of FEV(1) as the secondary outcome. In addition, the fraction of exhaled nitric oxide (FeNO) was measured before and after the challenges. In the 17 patients who met criteria for completion, no deleterious effect for S-albuterol was found for FEV(1) PC(30), AUC(0-40) FEV(1), or the FEV(1) slope(0-40). However, S-albuterol reduced the provocative concentration of methacholine to induce a 20% decrease in FEV(1) (PC(20) 0.52 +/- 2.06 vs 0.39 +/- 1.58 mg/ml, placebo vs S-albuterol, p=0.044) but did not affect FeNO.

CONCLUSION

A single high dose of S-albuterol did not alter the bronchodilator response to levalbuterol. The effect on bronchial responsiveness requires further study.

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.

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.

Review of guidelines and the literature in the treatment of acute bronchospasm in asthma

Asthma is a common chronic condition that disproportionately affects persons younger than 45 years. Asthma exacerbations can be sudden and severe, requiring treatment in the emergency department or hospitalization. Children younger than 15 years are 2-4 times more likely to have asthma as the first-listed hospital discharge diagnosis compared with those in other age groups. An estimated 12.8 million missed school days and 24.5 million lost work days due to asthma occurred in 2003. Drugs used in the treatment of acute asthma include inhaled beta(2)-agonists, oral corticosteroids, and inhaled anticholinergics. Levalbuterol was evaluated in several recent trials for treatment of asthma in the emergency department, for its effect in improving pulmonary function and on hospitalization rate. Theophylline, intravenous beta(2)-agonists, intravenous magnesium sulfate, and inhaled anesthetics have not been proven useful in the emergency management of asthma. The effectiveness of inhalation devices is dependent on age, cooperation of the patient, and technique.

Risk versus benefit considerations for the beta(2)-agonists

Short-acting beta(2)-agonists are the mainstay of therapy for acute bronchospasm associated with asthma and chronic obstructive pulmonary disease, whereas long-acting beta(2)-agonists are used in maintaining disease control in these respiratory disorders. This review describes and compares the pharmacology of the beta(2)-agonists and explains how these differences translate into differences in efficacy and beta(2)-adrenergic-mediated adverse effects. Questions commonly asked by clinicians regarding the efficacy and safety of short- and long-acting beta(2)-agonists include issues about cardiovascular effects, tolerance to their bronchodilator and bronchoprotective effects, blunting of albuterol response by long-acting beta(2)-agonists, potential masking of worsening asthma control, and the role of long-acting beta(2)-agonists as adjunctive therapy with inhaled corticosteroids in maintaining asthma control. Pharmacogenetics may play a role in determining which patients may be at risk for a reduced response to a beta(2)-agonist. The continued use of racemic albuterol, which contains a mixture of R-albuterol and S-albuterol, has been questioned because of data from preclinical and clinical studies suggesting that S-albuterol causes proinflammatory effects and may increase bronchial hyperreactivity. The preclinical and clinical effects of these two stereoisomers are reviewed. Data describing the efficacy and safety of levalbuterol (R-albuterol) and racemic albuterol are presented.

(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?"

Asthma pathophysiology and evidence-based treatment of severe exacerbations

PURPOSE

The pathogenesis of asthma and the treatment approach for acute exacerbations are described. The pharmacology, efficacy, safety, and cost of the beta2 agonist, albuterol, a racemic mixture of equal amounts of R- and S-enantiomers, and levalbuterol, the R-enantiomer, are compared.

SUMMARY

Asthma symptoms are the result of bronchial hyperresponsiveness, bronchospasm, and chronic airway inflammation. Short-acting, inhaled beta2 agonists; oxygen; intravenous fluids; and corticosteroids are the mainstays of treatment for acute exacerbations. The R-enantiomer of albuterol is responsible for bronchodilation. The S-enantiomer exhibits broncho-constricting activity in vitro, which may be mediated by muscarinic receptors and may be opposed by adding the anticholinergic agent ipratropium bromide. Levalbuterol improves pulmonary function to a greater extent than racemic albuterol and reduces the need for costly hospitalizations in patients with acute asthma exacerbations.

CONCLUSION

Levalbuterol is an alternative to racemic albuterol with the potential to improve patient outcomes and reduce costs in the treatment of acute asthma exacerbations.

Case studies illustrating the implementation of treatment strategies for acute and chronic asthma

PURPOSE

Considerations that enter into decisions about treatment strategies for acute and chronic asthma are illustrated in two case studies.

SUMMARY

A patient's signs, symptoms, vital signs, laboratory test results, recent history of illness or exposure to substances that can provoke asthma symptoms, and response to recently used asthma medications as well as efficacy, safety, and cost are important considerations in choosing drug therapy in the emergency department to treat an acute exacerbation. The need for a rapid onset of action and patient limitations may influence the choice of a dosage form, delivery device, and route of administration. Treatment strategies for patients with chronic asthma may require resolution of problems with adherence to the treatment plan or inhaler technique. Long-term control of asthma symptoms involves the use of preventive measures, including long-term-control medications, efforts to control asthma triggers, and self-monitoring of pulmonary function. Patient education and a written action plan are important elements of the treatment strategy.

CONCLUSION

An individualized approach to treating patients with acute or chronic asthma that takes into consideration patient-specific factors as well as efficacy, safety, and cost of drug therapy is needed when devising and implementing a treatment strategy to optimize patient outcomes.

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.

Assessing the effects of racemic and single-enantiomer albuterol on airway secretions in long-term intubated patients

OBJECTIVE

In vitro data suggest that the S-enantiomer of albuterol can induce mucociliary dysfunction. This clinical study assesses the clinical significance of standard doses of the S-enantiomer on airway secretions in long-term intubated patients by comparing a racemic formulation of albuterol, an R-enantiomer formulation, and normal saline solution.

DESIGN

A placebo-controlled crossover study.

PATIENTS

Fourteen stable intubated patients with a median duration of intubation of 21 months and a median age of 72 years.

SETTING

Long-term ventilator unit in skilled nursing facility.

INTERVENTIONS

Following a 2-week washout period during which regularly scheduled beta2-agonists were discontinued, tracheal aspirates were collected for 4 h/d for a 5-day period to establish baseline values, and the patients were then randomized in crossover manner to each of three nebulized treatments: normal saline solution, racemic albuterol, and R-albuterol. Each treatment was administered three times daily for 5 days, followed by a 2-day washout.

MEASUREMENTS

Tracheal aspirates were analyzed for volume, sodium, chloride, bicarbonate, interleukin (IL)-8, IL-1beta, soluble intercellular adhesion molecule, and tumor necrosis factor-alpha.

RESULTS

There were no consistent significant differences among the three treatment periods either in terms of volume of secretions or in the concentrations of the electrolytes or the inflammatory indexes. However, all three treatments, including saline solution, were associated with increased secretion volume after the first dose, but this effect was not apparent on subsequent doses.

CONCLUSION

There were no significant differences between racemic albuterol and R-albuterol observed in this study for any of the parameters studied, suggesting that the S-enantiomer does not adversely affect airway secretions at recommended doses. In addition, the routine administration of nebulized beta(2)-sympathomimetic agonists to stable patients undergoing prolonged intubation, for the sole purpose of changing the volume and composition of secretions of airway secretions, is not supported by the results of this study.

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.

Comparison of racemic albuterol and levalbuterol in the treatment of acute asthma in the ED

BACKGROUND

Acute asthma is often treated with racemic albuterol, a 1:1 mixture of (R)-albuterol and (S)-albuterol. Levalbuterol is the single-isomer agent comprised (R)-albuterol, an active bronchodilator, without any effects of (S)-albuterol.

OBJECTIVE

To compare emergency department (ED) admission rates of patients presenting with acute asthma who were treated with either racemic albuterol or levalbuterol.

SETTING

Suburban community teaching hospital.

DESIGN

Retrospective observational case review.

METHODS

Emergency department patients presenting with acute asthma at 2 different sites were reviewed over 9- and 3-month consecutive periods. Outcome measures included ED hospital admission rate, length of stay, arrival acuity, and treatment costs. Patients were excluded if younger than 1 year or if no treatment of acute asthma was rendered.

RESULTS

Of the initial 736 consecutive cases, significantly fewer admissions (4.7% vs 15.1%, respectively; P = .0016) were observed in the levalbuterol vs racemic albuterol group. Of the subsequent 186 consecutive cases, significantly fewer admissions were also observed (13.8% vs 28.9%, respectively; P = .021) in the levalbuterol vs racemic albuterol group. Treatment costs were lower with levalbuterol mainly because of a decrease in hospital admissions.

CONCLUSION

Levalbuterol treatment in the ED for patients with acute asthma resulted in higher patient discharge rates and may be a cost-effective alternative to racemic albuterol.

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.

Anti-inflammatory effect of albuterol enantiomers during respiratory syncytial virus infection in rats

Every year in the United States, respiratory syncytial virus (RSV) infections in infants and young children cause more than 120,000 hospitalizations, often complicated by the need for mechanical ventilation; yet no effective therapy is currently available for this disease. We showed previously that RSV infection is associated with neurogenic inflammation in the lower respiratory tract. In the present study, we sought to determine whether aerosolized beta(2)-receptor agonists inhibit neurogenic-mediated albumin extravasation in the airways of RSV-infected, mechanically ventilated rats, and to compare the anti-inflammatory effects of racemic albuterol ((RS)-albuterol) to its individual enantiomeric components (R)-albuterol and (S)-albuterol. Albumin extravasation evoked by sensorineural stimulation with capsaicin was inhibited only partially by 0.63 mg (RS)-albuterol, and higher doses had minimal incremental effects. In contrast, the anti-inflammatory effect of (R)-albuterol was already larger at the lowest dose of 0.31 mg, and complete inhibition of neurogenic exudation was observed at higher doses. (S)-albuterol had no significant inhibitory effect up to 1.25 mg, and had only partial inhibitory effect at higher doses. The anti-inflammatory effect of (R)-albuterol was independent from the expression of substance P neurokinin 1 receptors, suggesting a direct vascular effect. Our data show that (R)-albuterol has a much stronger inhibitory effect on neurogenic inflammation in RSV-infected airways when aerosolized in enantiomerically pure form, rather than in a racemic mixture with (S)-albuterol. Based on these data, we speculate that (R)-albuterol may be more effective than other adrenergic agents in the management of bronchiolitis.

Therapeutic responses in asthma and COPD. Bronchodilators

The presence of acute reversibility to bronchodilators does not distinguish asthma from COPD. Patients with either condition can benefit from bronchodilators, and should be given a trial to assess their response. Some respond with a change in lung volume with less hyperinflation; others improve their forced inspiratory flow and become much more comfortable. The combination of long-acting beta-agonists (LABAs) and inhaled steroids is useful in both conditions. While anticholinergics seem to yield the best results in COPD, some patients with asthma benefit from their use. Tiotropium may be the most effective agent as monotherapy in COPD, but the combination of an inhaled steroid and a LABA may produce similar results in improving lung function. Long-acting bronchodilators are effective agents as monotherapy in COPD, but in asthma should be combined with a controller medication. Short-acting beta-agonists should be used intermittently in asthma, but may be used regularly or combined with an anticholinergic in COPD. The roles of stereoisomers, leukotriene receptor antagonists, and type 4 phosphodiesterase inhibitors in asthma and COPD remain uncertain at this time.

Severe exacerbations of asthma

All asthmatics regardless of their perceived severity, are at risk of exacerbation, particularly if they are suboptimally treated in the outpatient arena. Fortunately most patients recover after administration of bronchodilators and anti-inflammatory medications, but preventable deaths continue to occur and refractory cases result in hospitalization and need for mechanical ventilation. We begin this article by reviewing the pathophysiology of acute exacerbations to build a foundation for the assessment of clinical status and to provide the rationale for a carefully contemplated and evidence-based therapeutic approach. We end this article with an in-depth examination of the particular problems that are encountered during mechanical ventilation and offer a strategy that helps minimize complications. In the final analysis, however, the greatest gains in the field of acute asthma will come not from its treatment but from its prevention by enhanced educational and environmental efforts and by the delivery of optimal medications at home.