Comparison of racemic albuterol and levalbuterol for treatment of acute asthma

Estimating the Economic Impact of Levalbuterol's Potential Transition From the National Reimbursement Drug List for the Treatment of Pediatric Asthma in China: A Budget Impact Analysis

Background Levalbuterol is a short-acting β2-agonist (SABA) indicated for treating or preventing asthma exacerbation. It was included in the 2020 Chinese National Reimbursement Drug List (NRDL). This study estimates the economic impact of levalbuterol's status change within and withdrawal from the NRDL in treating pediatric asthma from a publicly funded medical insurance perspective. Methodology A prevalence-based budget impact model was developed. The analysis compared a world with a levalbuterol scenario to a world without levalbuterol. Epidemiological data were obtained from the existing literature. Cost data were estimated based on the drug dosage in clinical trials, real-world settings, and expert opinions. Scenario analysis considered the same length of stay (LOS) in the two groups. One-way sensitivity analyses were carried out to show the impact of varying individual parameters. Results In the base-case analysis, compared to the world without scenario, the preservation of levalbuterol resulted in cost savings of ¥82.8 million in China over three years. In the scenario analysis, savings decreased to ¥76.1 million over three years. Sensitivity analysis showed that, for the most part, the results were robust to changes in input parameter values. Conclusions Using levalbuterol may lead to substantial cost savings for Chinese society.

State-of-the-art beta-adrenoreceptor agonists for the treatment of asthma

INTRODUCTION

Asthma, a heterogeneous disease, is characterized by chronic airway inflammation and hyperreactivity. β₂-adrenoreceptor agonists (β₂-agonists) remain pivotal for asthma management. Short-acting β₂-agonists (SABAs) result in rapid symptomatic alleviation and bronchospasm prevention. Patients experience significant clinical benefits from therapy with long-acting β₂-agonists (LABAs) with efficacy to bronchodilate, and prolonged lung function betterment. Recently discovered β₂-agonists with longer half-lives offer once-daily dosing.

AREAS COVERED

The authors provide a thorough review of the pharmacokinetics, pharmacodynamics, efficacy, tolerability, classification, and safety of β₂-agonists through an in-depth review of current literature using these databases: U.S. National Institutes of Health's National Library of Medicine (NIH/NLM), PubMed Central, and NLM clinical trials.

EXPERT OPINION

β₂- agonists act primarily on airway smooth muscle cells and are quintessential for adequate asthma management. Given their pharmacodynamic and pharmacokinetic properties, SABAs are used as rescue medication. Notably, the current Global Initiative for Asthma (GINA) strategy document recommends using LABA/inhaled corticosteroid combinations both as a daily controller and as a rescue medication. Clinicians should assess this new treatment plan on a per-case basis, making sure to evaluate inhaler adherence and treat modifiable risk factors. The development of next-generation β₂- agonists is an exciting research area that could significantly improve patients' adherence to treatment regimens and, consequently, asthma control and quality of life.

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.

Continuing to challenge practice to be evidence based

Practice habits continue in clinical practice despite the availability of research and other forms of evidence that should be used to guide critical care practice interventions. This article is based on a presentation at the 2014 National Teaching Institute of the American Association of Critical-Care Nurses. The article is part of a series of articles that challenge critical care nurses to examine the evidence guiding nursing practice interventions. Four common practice interventions are reviewed: (1) weight-based medication administration, (2) chest tube patency maintenance, (3) daily interruption of sedation, and (4) use of chest physiotherapy in children. For weight-based administration of medication, the patient's actual weight should be measured, rather than using an estimate. The therapeutic effectiveness and dosages of medications used in obese patients must be critically evaluated. Maintaining patency of chest tubes does not require stripping and milking, which probably do more harm than good. Daily interruption of sedation and judicious use of sedatives are appropriate in most patients receiving mechanical ventilation. Traditional chest physiotherapy does not help children with pneumonia, bronchiolitis, or asthma and does not prevent atelectasis after extubation. Critical care nurses are challenged to evaluate their individual practice and to adopt current evidence-based practice interventions into their daily practice.

Asthma Review for Pharmacists Providing Asthma Education

Asthma is the most common pediatric illness affecting more than 6 million children in the United States. Children with asthma have more frequent office visits and hospitalizations compared with adults. Despite advances in therapies, asthma still has a significant effect on the health care system. Regardless of the setting, pharmacists are uniquely equipped with an intimate knowledge of medications. With this knowledge, they can provide education to patients at various points throughout the health care system, from hospitalization to office visits to point of pick up at the pharmacy. The goal of this article is to equip the pharmacist with the necessary knowledge to provide education to these patients in a variety of practice settings, including community pharmacies, ambulatory care settings, and during transitions in care.

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.

Effects of (r,r)- and (r,r/s,s)-formoterol on airway relaxation and contraction in an experimental rat model

BACKGROUND

Racemic (R,R/S,S)-formoterol is a long-acting β-agonist composed of a 50:50 mixture of (R,R)- and (S,S)-enantiomers.

OBJECTIVE

The aim of this study was to determine whether (R,R)-formoterol and (R,R/S,S)-formoterol have differing effects on airway contraction and relaxation in vitro.

METHODS

Cylindrical airway segments 3-mm long were isolated from the mid-trachea of healthy Sprague-Dawley rats and placed in a modified Krebs-Henseleit solution. Dose-response curves of bethanechol-induced contraction (measured as milligrams of tension) and the concentration of bethanechol that elicited 50% to 75% of maximal contraction (EC50-75) were determined. The air-way cylinders were then precontracted with bethanechol at the EC50-75 and exposed to different concentrations of (R,R)-formoterol (0.0001-1.0 μM) or (R,R/S,S)-formoterol (0.0002-2.0 μM). Each concentration of the 2 formoterol formulations contained the same amount of (R,R)-enantiomer (eg, [R,R]-formoterol 0.0001 μM and [R,R/S,S]-formoterol 0.0002 1JM contained the same amount of [R,R]-enantiomer). The relaxation percentage in response to formoterol was calculated as a reduction in tension (in milligrams) in relation to baseline tension in the precontracted state, with each tracheal cylinder serving as its own control. To determine the effect of (R,R)-formoterol on airway contraction, tracheal cylinders were incubated with (R,R)- or (R,R/S,S)-formoterol before electrical field stimulation (EFS).

RESULTS

Tracheae from 56 three-week-old Sprague-Dawley rats were used in the study. The relaxation percentage of precontracted trachea was significantly greater after exposure to (R,R)-formoterol than to (R,R/S,S)-formoterol at a 2-fold higher concentration (P = 0.03; general linear model with repeated measures analysis comparing the 2 groups of animals). However, in a post hoc analysis, the mean (SE) relaxation percentage of precontracted trachea was significantly greater only after exposure to (R,R)-formoterol 0.01 μM than to (R,R/S,S)-formoterol 0.02 μM (15.6% [5.8%] vs 39.0% [5.6%]; P < 0.05, unpaired t test). EFS-induced airway contraction was significantly less in tracheal cylinders incubated in (R,R)-formoterol compared with those incubated in (R,R/S,S)-formoterol at a 2-fold higher concentration (P = 0.05; general linear model with repeated measures analysis comparing the 2 groups of animals). However, in the post hoc analysis, mean (SE) EFS-induced tracheal contraction was significantly less only in (R,R)-formoterol 0.01 μM compared with (R,R/S,S)-formoterol 0.02 μM at 10 V (1070 [55] mgvs 1225 [28] mg; P < 0.05, unpaired t test).

CONCLUSION

We found that (R,R)-formoterol may induce greater relaxation of precontracted airway smooth muscle cells than (R,R/S,S)-formoterol and that (R,R)-formoterol may have a greater inhibitory effect on the endogenous cholinergic and excitatory nonadrenergic, noncholinergic contractile airway responses than (R,R/S,S)-formoterol. We speculate that the presence of the (S,S)-enantiomer in (R,R/S,S)-formoterol may impair airway relaxation of pre-contracted trachea in rats.

Safety of Levalbuterol Compared to Albuterol in Patients With a Tachyarrhythmia

Objective: To determine the safety of levalbuterol versus albuterol in patients with a tachyarrhythmia. Data Sources: A PubMed search was conducted using the MeSH search terms levalbuterol, albuterol, and tachyarrhythmia. Bibliographies of relevant articles were reviewed for additional citations. Study Selection and Data Extraction: Search results were limited to humans and randomized controlled trials. Those studies that excluded patients with predetermined tachyarrhythmias were excluded from this review. Trials that failed to compare levalbuterol and albuterol outcomes were excluded. Data Synthesis: Beta-2 receptor agonists are the mainstay of treatment in patients with respiratory disease, such as asthma or chronic obstructive pulmonary disease. Racemic albuterol has been linked to poor outcomes due to the fact that it contains both the S-isomer and the R-isomer. Levalbuterol, the “pure” R-isomer, has been thought to decrease cardiac side effects since it only contains the therapeutic component of the racemic mixture. Patients with tachyarrhythmias are at an increased probability to experience harmful, if not fatal, cardiac side effects from these drugs. Limitations of current studies include a lack of data in patient populations with baseline tachyarrhythmias. Conclusions: Tachyarrhythmias put a patient at increased risk of poor outcomes, including death. Evidence for using either racemic albuterol or levalbuterol for respiratory disease management in these patients is lacking and insufficient. Randomized controlled trials show that in intensive care unit patient populations there is no clear advantage to using levalbuterol over albuterol; however, this did not hold true in pediatric populations. No clinical trials exist that look at a direct comparison of these 2 agents in patients with underlying tachyarrhythmias. Further research into the most efficacious and safe β-2 receptor agonists in this specialized patient population should be conducted to help reduce potential harmful outcomes.

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.

Childhood asthma: a guide for pediatric emergency medicine providers

Pediatric asthma is a disease that is managed across outpatient physicians, hospitalists, critical care physicians, and emergency department (ED) physicians. Scoring systems may facilitate a rapid assessment of the child with asthma in the ED. Short-acting beta agonists are still the mainstay of therapy for acute exacerbations along with corticosteroids and ipratropium bromide. ED providers must also know the indications for noninvasive ventilation and intubation. Most patients can be treated and discharged from the ED after acute exacerbation, and should be given a plan for going home that provides educational material and emergency scenarios to help prevent future acute incidents.

Asthma update

Asthma continues to be one of the most common reasons for emergency department visits and a leading cause of hospitalization. Acute management involves severity-based treatment of bronchoconstriction and underlying airway inflammation. Optimal treatment has been defined and standardized through randomized controlled trials, systematic reviews, and consensus guidelines. Implementation of clinical practice guidelines may improve clinical, quality, and safety outcomes. Asthma morbidity is disproportionately high in poor, urban, and minority children. Children treated in emergency departments commonly have persistent chronic severity, significant morbidity, and infrequent follow-up and primary asthma care, and prescription of inhaled corticosteroids is appropriate.

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.

Levalbuterol versus albuterol for acute asthma: a systematic review and meta-analysis

BACKGROUND

Conventional albuterol is a racemic mixture of (S)-albuterol and (R)-albuterol (levalbuterol). Levalbuterol is therapeutically active component of albuterol whereas (S)-albuterol is considered inert with some unwanted effects.

OBJECTIVES

To evaluate efficacy and safety of levalbuterol versus albuterol in acute asthma.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Pubmed and Cochrane databases. TRIAL ELIGIBILITY CRITERIA, PARTICIPANTS, AND INTERVENTIONS: Randomized control trials comparing levalbuterol versus albuterol for acute asthma in all age groups. DATA EXTRACTION AND RESULT SYNTHESIS: Two authors extracted data independently. Meta-analyses were performed using Review Manager Software.

RESULTS

Seven trials including a total of 1625 participants fulfilled the eligibility criteria. Respiratory rate, oxygen saturation, and percentage change in FEV1 and clinical asthma score were not significantly different between the groups with mean difference (95% CI) of 0.35 (-0.81, 1.51), -0.29 (-0.68, 0.10), -28.3 (-59.95, 3.33) and -1.01 (-5.30, 3.28) respectively. There were no significant differences in side effects between groups.

LIMITATIONS

Data were not available for two probable eligible trials. A few assumptions and some calculated values were used for meta-analysis.

CONCLUSIONS

Levalbuterol was not superior to albuterol regarding efficacy and safety in subjects with acute asthma. We suggest that levalbuterol should not be used over albuterol for acute asthma.

Comparison of levalbuterol and racemic albuterol based on cardiac adverse effects in children

OBJECTIVE

To compare the cardiac effects of levalbuterol with those of racemic albuterol based on changes in heart rate (HR) in pediatric patients.

METHODS

The medical records of hospitalized children ages 1 month to 12 years, who received either levalbuterol or racemic albuterol via nebulizer for 3 consecutive doses between January 2006 and December 2008 were reviewed. The documented HR was collected prior to and after each administered dose of bronchodilator. The primary outcome was the largest percentage of change in HR between groups. Secondary outcomes of comparisons of the number of patients who had more than a 10% change in HR and incidence of tachycardia were included.

RESULTS

A total of 50 patients, 25 in each group, was included in the study. All patients in the racemic albuterol group received 2.5 mg per dose, while most of the patients in the levalbuterol group received 0.63 mg per dose (19 patients, 76%). Only 6 levalbuterol patients received a dose of 1.25 mg. Nineteen of 25 patients (76%) in the levalbuterol group were tachycardic prior to the first recorded dose compared to 15 patients (60%) in the racemic albuterol group (p = 0.36). The median of the largest percentage of change in HR was 4.1% (interquartile range [IQR], 1.8-8.7) in the levalbuterol group compared to 5% (IQR, 1.9-7.8) in the racemic albuterol group (p = 0.763). Four patients in the levalbuterol group experienced an HR increase of more than 10% compared to 5 patients in the racemic albuterol group (p = 1.0).

CONCLUSION

Levalbuterol and racemic albuterol bronchodilator therapies produced similar effects on HR. No clinically significant differences were detected in HR changes between the two treatment groups, despite administration of a larger equipotent albuterol dose in the racemic albuterol group than in the levalbuterol group.

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.

Common pediatric respiratory emergencies

Pediatric respiratory illnesses are a huge burden to emergency departments worldwide. This article reviews the latest evidence in the epidemiology, assessment, management, and disposition of children presenting to the emergency department with asthma, croup, bronchiolitis, and pneumonia.

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.

Severe Asthma

Despite vast improvements in the care of children with asthma over the past decades, asthma remains a common cause of admission to pediatric intensive care units. During the 1990s asthma prevalence and hospital admissions increased in the United States and worldwide. The increase occurred in both males and females and across all ethnic groups. However, the largest increases occurred in children of low socioeconomic status living in urban settings. Recent asthma statistics should be interpreted with consideration of changes made in the method for reporting asthma prevalence (Fig. 23-1). From 1980 to 1996, the National Health Interview Survey (NHIS) conducted by the CDC measured pediatric asthma prevalence as the percentage of children with asthma in the past 12 months. Since 1997, asthma prevalence estimates have been defined as: having received an asthma diagnosis, currently having the disease at the time of the interview, and experiencing an attack in the past year. The more specific definition may have led to a reduction in the number of children reported to have asthma.

Management of severe asthma exacerbation in children

BACKGROUND

Asthma is a common disease in children and acute severe asthma exacerbation can be life-threatening. This article aims to review recent advances in understanding of risk factors, pathophysiology, diagnosis and treatment of severe asthma exacerbation in children.

DATA SOURCES

Articles concerning severe asthma exacerbation in children were retrieved from PubMed. Literatures were searched with MeSH words "asthma", "children", "severe asthma exacerbation" and relevant cross references.

RESULTS

Severe asthma exacerbation in children requires aggressive treatments with β2-agonists, anticholinergics, and corticosteroids. Early initiation of inhaled β-agonists and systemic use of steroids are recommended. Other agents such as magnesium and aminophylline have some therapeutic benefits. When intubation and mechanical ventilation are needed, low tidal volume, controlled hypoventilation with lower-than-traditional respiratory rates and permissive hypercapnia can be applied.

CONCLUSIONS

Researchers should continue to detect the risk factors, pathophysiology, diagnosis and treatment of severe asthma exacerbation in children. More studies especially randomized controlled trials are required to evaluate the efficacy and safety of standard and new therapies.

(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.

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.

The effects of racemic albuterol versus levalbuterol in very low birth weight infants

Bronchodilators have been used in premature infants. Levalbuterol (LEV) an R-isomer of Albuterol has fewer hemodynamic side effects than Racemic Albuterol (RAC) in adults and children. In a retrospective study we sought to investigate the effects of LEV (0.31 mg) versus RAC (1.25 mg) in very low-birth weight infants (VLBW) who were treated with a beta-2 agonist for > or =2 weeks. Medical records (between January 2001 and December 2006) were reviewed for patients' demographics, medications use, hemodynamic and respiratory parameters, hypokalemia and hyperglycemia. Among 811 VLBW infants who were admitted to our NICU, 16 infants received RAC and 31 infants received LEV for > or =2 weeks. Infants who received RAC were younger, smaller, and received less Ipratropium Bromide (IB) than infants who received LEV [26.1 +/- 1.2 weeks vs. 28.1 +/- 3.7 weeks (P = 0.01), 817 +/- 211 g vs. 1,127 +/- 589 g (P = 0.01) and 2/16 (12%) vs. 15/31 (48%; P = 0.01); respectively]. In infants treated exclusively with RAC or LEV without IB, mean arterial blood pressures were lower in the RAC (n = 14) than the LEV group (n = 16, P = 0.05 by general linear model with repeated measures); however there were no differences in daily heart rates, oxygen supplementations, oxygen saturations, or respiratory rates. Also there were no differences between the two groups in hypokalemia or hyperglycemia. We conclude that LEV at a dose of 0.31 mg might have an indication in VLBW infants who are at risk for hemodynamic instability.

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.

Evaluation of the Efficacy and Safety of Levalbuterol in Subjects with COPD

The efficacy and safety of nebulized levalbuterol in adults with chronic obstructive pulmonary disease (COPD) was evaluated in this multicenter, randomized, double-blind, parallel design study. Randomized subjects (n = 209) received levalbuterol (LEV) 0.63 mg or 1.25 mg, racemic albuterol (RAC) 2.5 mg, or placebo (PBO) TID for 6 weeks. Serial spirometry was completed in-clinic after study drug alone (weeks 0, 2, and 6) or in combination with ipratropium bromide 0.5 mg (week 4). The primary endpoint was the averaged FEV1 AUC(0-8 hrs) over weeks 0, 2 and 6 compared with placebo. Other endpoints included rescue medication use, safety parameters, COPD exacerbations, and global evaluations. All active treatments demonstrated improvements in the percent change in FEV1 AUC(0-8 hrs) over the double-blind period and at each visit vs PBO (p < 0.05). Rescue medication use vs. baseline (doses/day) changed over time: PBO +0.38 +/- 3.3; LEV 0.63 mg +0.07 +/- 3.3; LEV 1.25 mg -0.84 +/- 3.8 (p = 0.02 vs. RAC); RAC +0.97 +/- 2.5. The overall rate of adverse events was PBO 56.4%, LEV 0.63 mg 56.6%, LEV 1.25 mg 67.3%, and RAC 65.4%. Protocol-defined COPD exacerbations occurred in all groups (PBO 12.7%, LEV 0.63 mg 11.3%; LEV 1.25 mg 18.4%; RAC 21.2%). Withdrawals due to COPD exacerbations were significantly higher in the RAC group compared with PBO (PBO 0%; LEV 0.63 mg 1.9%; LEV 1.25 mg 4.1%; RAC 9.6% p = 0.01 vs. PBO). In this study, levalbuterol treatment in subjects with COPD was generally well tolerated, produced significant bronchodilation compared with PBO, and improved clinical control of COPD as evidenced by reductions in rescue medication use compared with PBO and/or RAC.

Pediatric asthma and related allergic and nonallergic diseases: patient-oriented evidence-based essentials that matter

Asthma is the most common medical diagnosis among hospitalized children. In the USA, asthma has accounted for approximately 15% of nonsurgical admissions to hospital in the pediatric age group. Asthma is also one of the leading causes for emergency care requirements, one of the leading causes for missed school, and a cause for considerable morbidity, disability and occasional mortality at all ages. Despite these discouraging statistics, convincing data indicate that this failure of asthma management is not the result of inadequate therapeutic potential, but instead represents ineffective delivery of medical care. Management of asthma and its major co-morbidities, allergic and nonallergic rhinitis, and atopic dermatitis requires a knowledge of the alternative therapies, natural history, and educational techniques for providing patients and families with the ability to manage these troublesome chronic disorders.

Airway clearance techniques to treat acute respiratory disorders in previously healthy children: where is the evidence?

Airway clearance techniques are an important part of the respiratory management in children with cystic fibrosis, bronchiectasis and neuromuscular disease. They are also, however, frequently prescribed in previously healthy children with an acute respiratory problem with the aim to speed up recovery. The current review explores the evidence behind this use of airway clearance techniques in children without underlying disease. Few studies have been performed; many different techniques are available and the therapies used are often poorly specified. It is necessary to name the specific airway clearance technique used in treatment rather than to just state "chest physiotherapy," a term that is often confused with chest clapping or vibration plus postural drainage. There is little evidence that airway clearance techniques play a role in the management of children with an acute respiratory problem. Physicians routinely prescribing airway clearance techniques in previously healthy children should question their practice.

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.

[Management of acute asthma exacerbations in pediatrics]

Despite the significant advances that have been produced in the management of asthma in the last few decades, crises, attacks, or asthma exacerbations (acute asthma) continue to be the most common cause of consultation in pediatric emergency units. Visits to these units and hospital admissions due to acute asthma represent three quarters of the direct costs due to this disease. Acute asthma is a medical emergency that should be rapidly diagnosed and treated. Evaluation of children with acute asthma exacerbations should consist of two phases: a static phase (determination of the severity of the crisis on admission) and a dynamic phase (treatment response). The present article provides an in-depth review and analysis of current pharmacological and nonpharmacological treatments (oxygen, bronchodilators, corticosteroids - inhaled and systemic - aminophylline, magnesium sulfate, etc.) of acute asthma exacerbations and proposes management protocols for use in both primary care and emergency units.

Asthma

Asthma has been recognized as a disease since the earliest times. In the Corpus Hippocraticum, Hippocrates used the term “ασθμα” to indicate any form of breathing difficulty manifesting itself by panting. Aretaeus of Cappadocia, a well-known Greek physician (second century A.D.), is credited with providing the first detailed description of an asthma attack [13], and to Celsus it was a disease with wheezing and noisy, violent breathing. In the history of Rome, we find many members of the Julio-Claudian family affected with probable atopic respiratory disorders: Caesar Augustus suffered from bronchoconstriction, seasonal rhinitis as well as a highly pruritic skin disease. Claudius suffered from rhinoconjunctivitis and Britannicus was allergic to horse dander [529]. Maimonides (1136–1204) warned that to neglect treatment of asthma could prove fatal, whereas until the 19th century, European scholars defined it as “nervous asthma,” a term that was given to mean a defect of conductivity of the ninth pair of cranial nerves.

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.

The value of care algorithms

The use of protocols or care algorithms in medical facilities has increased in the managed care environment. The definition and application of care algorithms, with a particular focus on the treatment of acute bronchospasm, are explored in this review. The benefits and goals of using protocols, especially in the treatment of asthma, to standardize patient care based on clinical guidelines and evidence-based medicine are explained. Ideally, evidence-based protocols should translate research findings into best medical practices that would serve to better educate patients and their medical providers who are administering these protocols. Protocols should include evaluation components that can monitor, through some mechanism of quality assurance, the success and failure of the instrument so that modifications can be made as necessary. The development and design of an asthma care algorithm can be accomplished by using a four-phase approach: phase 1, identifying demographics, outcomes, and measurement tools; phase 2, reviewing, negotiating, and standardizing best practice; phase 3, testing and implementing the instrument and collecting data; and phase 4, analyzing the data and identifying areas of improvement and future research. The experiences of one medical institution that implemented an asthma care algorithm in the treatment of pediatric asthma are described. Their care algorithms served as tools for decision makers to provide optimal asthma treatment in children. In addition, the studies that used the asthma care algorithm to determine the efficacy and safety of ipratropium bromide and levalbuterol in children with asthma are described.

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.

(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?"