Modulation of T-cell function by (R)- and (S)-isomers of albuterol: anti-inflammatory influences of (R)-isomers are negated in the presence of the (S)-isomer

Beta2-Adrenergic Suppression of Neuroinflammation in Treatment of Parkinsonism, with Relevance for Neurodegenerative and Neoplastic Disorders

There is a preliminary record suggesting that β2-adrenergic agonists may have therapeutic value in Parkinson's disease; recent studies have proposed a possible role of these agents in suppressing the formation of α-synuclein protein, a component of Lewy bodies. The present study focuses on the importance of the prototypical β2-adrenergic agonist epinephrine in relation to the incidence of Parkinson's disease in humans, and its further investigation via synthetic selective β2-receptor agonists, such as levalbuterol. Levalbuterol exerts significant anti-inflammatory activity, a property that may suppress cytokine-mediated degeneration of dopaminergic neurons and progression of Parkinsonism. In a completely novel finding, epinephrine and certain other adrenergic agents modeled in the Harvard/MIT Broad Institute genomic database, CLUE, demonstrated strong associations with the gene-expression signatures of anti-inflammatory glucocorticoids. This prompted in vivo confirmation in mice engrafted with human peripheral blood mononuclear cells (PBMCs). Upon toxic activation with mononuclear antibodies, levalbuterol inhibited (1) the release of the eosinophil attractant chemokine eotaxin-1, which is implicated in CNS and peripheral inflammatory disorders, (2) elaboration of the tumor-promoting angiogenic factor VEGFa, and (3) release of the pro-inflammatory cytokine IL-13 from activated PBMCs. These observations suggest possible translation to Parkinson's disease, other neurodegenerative syndromes, and malignancies, via several mechanisms.

A Systematic Review of Inverse Agonism at Adrenoceptor Subtypes

As many, if not most, ligands at G protein-coupled receptor antagonists are inverse agonists, we systematically reviewed inverse agonism at the nine adrenoceptor subtypes. Except for β3-adrenoceptors, inverse agonism has been reported for each of the adrenoceptor subtypes, most often for β2-adrenoceptors, including endogenously expressed receptors in human tissues. As with other receptors, the detection and degree of inverse agonism depend on the cells and tissues under investigation, i.e., they are greatest when the model has a high intrinsic tone/constitutive activity for the response being studied. Accordingly, they may differ between parts of a tissue, for instance, atria vs. ventricles of the heart, and within a cell type, between cellular responses. The basal tone of endogenously expressed receptors is often low, leading to less consistent detection and a lesser extent of observed inverse agonism. Extent inverse agonism depends on specific molecular properties of a compound, but inverse agonism appears to be more common in certain chemical classes. While inverse agonism is a fascinating facet in attempts to mechanistically understand observed drug effects, we are skeptical whether an a priori definition of the extent of inverse agonism in the target product profile of a developmental candidate is a meaningful option in drug discovery and development.

Effect of (R)-salbutamol on the switch of phenotype and metabolic pattern in LPS-induced macrophage cells

Evidence demonstrates that M1 macrophage polarization promotes inflammatory disease. Here, we discovered that (R)‐salbutamol, a β₂ receptor agonist, inhibits and reprograms the cellular metabolism of RAW264.7 macrophages. (R)‐salbutamol significantly inhibited LPS‐induced M1 macrophage polarization and downregulated expressions of typical M1 macrophage cytokines, including monocyte chemotactic protein‐1 (MCP‐1), interleukin‐1β (IL‐1β) and tumour necrosis factor α (TNF‐α). Also, (R)‐salbutamol significantly decreased the production of inducible nitric oxide synthase (iNOS), nitric oxide (NO) and reactive oxygen species (ROS), while increasing the reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio. In contrast, (S)‐salbutamol increased the production of NO and ROS. Bioenergetic profiles showed that (R)‐salbutamol significantly reduced aerobic glycolysis and enhanced mitochondrial respiration. Untargeted metabolomics analysis demonstrated that (R)‐salbutamol modulated metabolic pathways, of which three metabolic pathways, namely, (a) phenylalanine metabolism, (b) the pentose phosphate pathway and (c) glycerophospholipid metabolism were the most noticeably impacted pathways. The effects of (R)‐salbutamol on M1 polarization were inhibited by a specific β₂ receptor antagonist, ICI‐118551. These findings demonstrated that (R)‐salbutamol inhibits the M1 phenotype by downregulating aerobic glycolysis and glycerophospholipid metabolism, which may propose (R)‐salbutamol as the major pharmacologically active component of racemic salbutamol for the treatment of inflammatory diseases and highlight the medicinal value of (R)‐salbutamol.

Recruitment of β-arrestin 1 and 2 to the β2-adrenoceptor: analysis of 65 ligands

Beyond canonical signaling via Gαs and cAMP, the concept of functional selectivity at β2-adrenoceptors (β2ARs) describes the ability of adrenergic drugs to stabilize ligand-specific receptor conformations to initiate further signaling cascades comprising additional G-protein classes or β-arrestins (βarr). A set of 65 adrenergic ligands including 40 agonists and 25 antagonists in either racemic or enantiopure forms was used for βarr recruitment experiments based on a split-luciferase assay in a cellular system expressing β2AR. Many agonists showed only (weak) partial agonism regarding βarr recruitment. Potencies and/or efficacies increased depending on the number of chirality centers in (R) configuration; no (S)-configured distomer was more effective at inducing βarr recruitment other than the eutomer. βarr2 was recruited more effectively than βarr1. The analysis of antagonists revealed no significant effects on βarr recruitment. Several agonists showed preference for activation of Gαs GTPase relative to βarr recruitment, and no βarr-biased ligand was identified.

IN CONCLUSION

1) agonists show strong bias for Gαs activation relative to βarr recruitment; 2) agonists recruit βarr1 and βarr2 with subtle differences; and 3) there is no evidence for βarr recruitment by antagonists.

Proof-of-concept evaluation of trough airway hyper-responsiveness following regular racemic or levosalbutamol in genotype-stratified steroid-treated persistent asthmatic patients

Asthmatic patients receiving ICSs (inhaled corticosteroids) may take frequent add-on therapy with salbutamol despite on-demand prescription. Frequent salbutamol use can be detrimental in asthma. The isomeric formulation of salbutamol and the B2ADR (β2 adrenoceptor) 16 genotype may also influence this phenomenon. We performed a randomized, double-blind, placebo-controlled, triple crossover, proof of concept trial comparing 2 weeks of regular therapy with inhaled racemic salbutamol [200 μg q.i.d. (four times daily)], levosalbutamol (100 μg q.i.d.) or placebo on trough methacholine PC20 [provocative concentration causing 20% fall in FEV1 (forced expiratory volume in 1 s)] 6 h post-dose (the primary outcome) in 30 persistent asthmatic patients (15 who were Arg16 homozygous and 15 who were Gly16 homozygous) all receiving ICSs. There was no worsening of AHR (airway hyper-responsiveness) at trough to methacholine after 2 weeks regular exposure to either racemic (P=0.53) or levosalbutamol (P=0.84) compared with placebo, nor between genotypes-as dd (doubling dilution) difference in methacholine PC20 from placebo [salbutamol/Arg16=0.36 dd [95% CI (confidence interval), -0.43, 1.15]; salbutamol/Gly16=0.01 dd (95% CI, -0.47, 0.49); levosalbutamol/Arg16=-0.01 dd (95% CI, -0.89, 0.87); and levosalbutamol/Gly16=0.28 dd (95% CI, -0.22, 0.77)]. Both active treatments improved morning PEF (peak expiratory flow) in Gly16 (P=0.04 overall) but not Arg16 (P=0.50 overall) patients, whereas evening PEF improved in both Gly16 (P<0.001 overall) and Arg16 (P=0.006 overall) patients. In conclusion, the regular exposure to either racemic or levosalbutamol for 2 weeks added to ICSs did not cause worsening of AHR at trough compared with placebo; with no difference seen between B2ADR 16 genotypes.

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.

β2-Agonists inhibit TNF-α-induced ICAM-1 expression in human airway parasympathetic neurons

Background

Major basic protein released from eosinophils to airway parasympathetic nerves blocks inhibitory M₂ muscarinic receptors on the parasympathetic nerves, increasing acetylcholine release and potentiating reflex bronchoconstriction. Recruitment of eosinophils to airway parasympathetic neurons requires neural expression of both intercellular adhesion molecular-1 (ICAM-1) and eotaxin. We have shown that inflammatory cytokines induce eotaxin and ICAM-1 expression in parasympathetic neurons.

Objective

To test whether the β₂ agonist albuterol, which is used to treat asthma, changes TNF-alpha-induced eotaxin and ICAM-1 expression in human parasympathetic neurons.

Methods

Parasympathetic neurons were isolated from human tracheas and grown in serum-free medium for one week. Cells were incubated with either (R)-albuterol (the active isomer), (S)-albuterol (the inactive isomer) or (R,S)-albuterol for 90 minutes before adding 2 ng/ml TNF-alpha for another 4 hours (for mRNA) or 24 hours (for protein).

Results and Conclusions

Baseline expression of eotaxin and ICAM-1 were not changed by any isomer of albuterol as measured by real time RT-PCR. TNF-alpha induced ICAM-1 expression was significantly inhibited by (R)-albuterol in a dose dependent manner, but not by (S) or (R,S)-albuterol. Eotaxin expression was not changed by TNF-alpha or by any isomer of albuterol. The β-receptor antagonist propranolol blocked the inhibitory effect of (R)-albuterol on TNF-alpha-induced ICAM-1 expression.

Clinical Implication

The suppressive effect of (R)-albuterol on neural ICAM-1 expression may be an additional mechanism for decreasing bronchoconstriction, since it would decrease eosinophil recruitment to the airway nerves.

Racemic salbutamol and levosalbutamol in mild persistent asthma: A comparative study of efficacy and safety

Aim:

The effect of monotherapy with racemic salbutamol and levosalbutamol on symptoms, quality of life, and pulmonary function has been assessed and compared in mild persistent asthma.

Materials and Methods:

A randomized, open, parallel clinical study was conducted on 60 patients of mild persistent asthma. After baseline assessments, salbutamol was prescribed to 30 patients and levosalbutamol to another 30 for 4 weeks. The efficacy variables were change in asthma symptom scoring, pulmonary function test, and Mini Asthma Quality of Life Questionnaire (MiniAQLQ) scoring. At follow-up, the patients were re-evaluated and analyzed by statistical tools.

Results:

Shortness of breath (P<0.001), chest tightness (P=0.033), wheeze (P=0.01), cough (P=0.024), and overall asthma symptom score (P<0.001) were significantly decreased in the levosalbutamol group in comparison to the salbutamol group. Results of MiniAQLQ revealed that improvement in symptoms (P=0.018), activity limitations (P=0.03), environmental stimuli (P=0.013)-related scoring and overall MiniAQLQ scoring (P<0.001) was statistically significant in the levosalbutamol group. Percentage reversibility of forced expiratory volume at one second (P=0.034), forced vital capacity (P=0.029), peak expiratory flow rate (P=0.0003) was found to be superior in the levosalbutamol group.

Conclusion:

Levosalbutamol was found to be superior compared to recemic salbutamol in mild persistent asthma.

Anti-inflammatory and antinociceptive effects of salbutamol on acute and chronic models of inflammation in rats: involvement of an antioxidant mechanism

The possible role of β-2 adrenergic receptors in modulation of inflammatory and nociceptive conditions suggests that the β-2 adrenergic receptor agonist, salbutamol, may have beneficial anti-inflammatory and analgesic effects. Therefore, in this study, we induced inflammatory and nociceptive responses with carrageenan-induced paw edema or cotton-pellet-induced granuloma models, both of which result in oxidative stress. We hypothesized that salbutamol would prevent inflammatory and nociceptive responses by stimulating β-2 adrenergic receptors and the prevention of generation of ROS during the acute inflammation process in rats. Both doses of salbutamol used in the study (1 and 2 mg/kg) effectively blocked the acute inflammation and inflammatory nociception induced by carrageenan. In the cotton-pellet-induced granuloma test, both doses of salbutamol also significantly decreased the weight of granuloma tissue on the cotton pellets when compared to the control. Anti-inflammatory and analgesic effects of salbutamol were found to be comparable with those of indomethacin. Salbutamol decreased myeloperoxidase (MPO) activity and lipid peroxidation (LPO) level and increased the activity of superoxide dismutase (SOD) and level of glutathione (GSH) during the acute phase of inflammation. In conclusion, salbutamol can decrease acute and chronic inflammation, possibly through the stimulation of β-2 adrenergic receptors. This anti-inflammatory effect may be of significance in asthma treatment, where inflammation also takes part in the etiopathology. This study reveals that salbutamol has significant antioxidative effects, which at least partially explain its anti-inflammatory capabilities. These findings presented here may also shed light on the roles of β-2 adrenergic receptors in inflammatory and hyperalgesic conditions.

Levosalbutamol for chronic obstructive pulmonary disease: a treatment evaluation

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Albuterol isomers modulate platelet-activating factor synthesis and receptor signaling in human bronchial smooth muscle cells

BACKGROUND

Racemic albuterol is a 50:50 mixture of the (R)- and (S)-enantiomers of albuterol. Its clinical efficacy resides in the (R)-enantiomer (levalbuterol). Studies have shown that (S)-albuterol induces human bronchial smooth muscle cell (HBSMC) proliferation via a pathway linked to platelet-activating factor (PAF), but the underlying mechanism by which (S)-albuterol augments PAF effects is not clear. In this study, we compared effect of levalbuterol and (S)-albuterol on PAF receptor (PAFr)-mediated signaling and PAF metabolism by HBSMCs after incubation with the albuterol isomers.

METHODS

PAF binding and inositol phosphate (IP(3)) release were studied on adherent cultured cells. PAFr protein expression was measured by Western blotting, PAF synthesis and catabolism were measured in membrane and cytosolic proteins of cells incubated with albuterol isomers.

RESULTS

Compared to control conditions, (S)-albuterol increased PAF binding by 70% after 30 min of preincubation and by 150% after 24 h of preincubation. Levalbuterol had no effect on PAF binding under both conditions. (S)-albuterol also augmented PAF stimulation of IP(3) release, while levalbuterol and the racemic mixture had no effect. WEB 2170, a PAFr antagonist, inhibited the ability of (S)-albuterol to increase PAF binding or stimulate IP(3) release. (S)-albuterol stimulated PAFr protein expression. With PAF metabolism, (S)-albuterol treatment augmented PAF synthesis, but significantly inhibited PAF catabolism.

CONCLUSIONS

Our data suggest that one mechanism by which (S)-albuterol stimulates HBSMC proliferation involves upregulation of PAFr-mediated effects including increased PAF synthesis and decreased PAF catabolism.

(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.

Evaluation of the effects of the R- and S-enantiomers of salbutamol on equine isolated bronchi

BACKGROUND

Equine obstructive pulmonary disease, also known as heaves or recurrent airway obstruction (RAO) is a common equine pulmonary disease with some similarities to human asthma and COPD, which represents a major cause of morbidity and loss of lung performance. Salbutamol has been widely used for the treatment of human airway diseases and has usually been prepared as the racemic form of the drug. However, recently the R-enantiomer of salbutamol has been introduced into clinical practice in the treatment of asthma in humans and this has been suggested to be an improvement on the racemic form of the drug; therefore thus the S-enantiomer has been demonstrated to have adverse effects in the lung and thus using the R-enantiomer may improve the therapeutic ratio. However, little is known about the properties of the R- and S-enantiomers of salbutamol in equine airways and the present study has evaluated the relaxant effects of racemic β(2)-agonists in comparison with the R- and S-enantiomers in isolated equine isolated bronchi, as well as the bronchoprotective effects of these drugs on cholinergic and histaminergic pathway.

METHODS

We have studied the effects of the R- and S-enantiomers of salbutamol on bronchi isolated from RAO-affected or unaffected horses. The first study assayed the relaxant effects of R- and S-salbutamol on isolated bronchial rings contracted with carbachol or histamine at a sub-maximal concentration (EC70). A second study evaluated the effects of R- and S-salbutamol on semi-logarithmic cumulative concentration-response curves induced by carbachol or histamine. Specific software was used to calculate statistical significance and the appropriate sigmoidal curve-fitting model.

RESULTS

Neither enantiomers of salbutamol caused a relaxant effect on the sub-maximal plateau contractile effects of carbachol; in fact, both R- and S-salbutamol induced a slight, but significant contraction (P ≤ 0.05) compared to the controls. In contrast, R-salbutamol induced a significant relaxation of bronchi pre-contracted with histamine (RAO-unaffected: 92.06% ± 2.00; RAO-affected 100.20 ± 3.99; P ≤ 0.01). S-salbutamol induced a weak relaxation (RAO-unaffected: 15.81% ± 5.65; RAO-affected 12.36 ± 5.15) when compared to that induced by papaverine. The incubation with either R- or S-salbutamol shifted rightward (P ≤ 0.001) the carbachol contraction curve in RAO-unaffected bronchi, but not in RAO-affected bronchi, compared to control tissues. R-salbutamol induced a reduction in E(max) values (C: 9.07 gr ± 0.68; R-salb.: 6.36 gr ± 0.21; P ≤ 0.01) in normal bronchi. On the contrary it reduced the histamine potency in RAO-affected bronchi (EC50 7.10 μM ± 0.35, P < 0.001). The incubation with S-salbutamol shifted leftward the histamine concentration curve in both normal bronchi (C: 7.00 μM ± 0.29; S-salb.: 2.25 μM ± 0.19; P ≤ 0.001) and bronchi from RAO-affected horses (C: 2.80 μM ± 0.26; S-salb.: 1.50 μM ± 0.80; P ≤ 0.05).

CONCLUSION

Our studies have demonstrated that S-salbutamol elicited a modest increase in contraction of equine airway smooth muscle induced by carbachol and induced a significant hyperresponsiveness to histamine. These results confirm the ability of the S-enantiomer of salbutamol to potentiate the contractile effect of certain spasmogens on airway smooth muscle. Such an adverse effect would be determined in the airways of horses with RAO and suggest that if salbutamol is to be used in the treatment of symptoms of RAO in horses, the R-enantiomer, rather than the racemic mixture should be considered.

Regulation of T cells in airway disease by beta-agonist

It is widely recognized that Th2 cytokines derived from T cells play a major role in the development of allergic lung inflammation that causes most asthma. Beta-agonists are important rescue and maintenance therapies for asthma, yet our understanding of beta-agonist effects on T cell biology is surprisingly poor. Recent studies using both cell culture and more integrative models are beginning to reveal beta-agonist regulation of T cell signaling and function that may be important in the pathogenesis and treatment of asthma and possibly other inflammatory diseases. Here we provide a comprehensive review of the literature concerning beta-agonist effects on T cells, and discuss the relevance of emerging paradigms of beta-adrenergic receptor signaling to T cell function.

beta2-agonists promote host defense against bacterial infection in primary human bronchial epithelial cells

Background

Airway epithelial cells are critical in host defense against bacteria including Mycoplasma pneumoniae (Mp) in chronic obstructive pulmonary disease (COPD) and asthma. β2-agonists are mainstay of COPD and asthma therapy, but whether β2-agonists directly affect airway epithelial host defense functions is unclear.

Methods

Epithelial cells from bronchial brushings of normal (n = 8), asthma (n = 8) and COPD (n = 8) subjects were grown in air-liquid interface cultures, and treated with cigarette smoke extract (CSE) and/or Th2 cytokine IL-13, followed by Mp infection and treatment with β2-agonists albuterol and formoterol for up to seven days. Mp and host defense proteins short palate, lung, and nasal epithelial clone 1 (SPLUNC1) and β-defensin-2 were quantified. Expression of β2-adrenergic receptors was also measured by real-time quantitative RT-PCR.

Results

(R)- or racemic albuterol and (R,R)- or racemic formoterol significantly decreased Mp levels in normal and asthma epithelial cells. Normal cells treated with Mp and (R)- or racemic albuterol showed an increase in SPLUNC1, but not in β-defensin-2. COPD cells did not respond to drug treatment with a significant decrease in Mp or an increase in SPLUNC1. IL-13 attenuated drug effects on Mp, and markedly decreased SPLUNC1 and β2-adrenergic receptors.

Conclusions

These results for the first time show that β2-agonists enhance host defense functions of primary bronchial epithelial cells from normal and asthma subjects, which is attenuated by IL-13.

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.

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.

A randomized controlled trial of R-salbutamol for topical treatment of discoid lupus erythematosus

BACKGROUND

In a recent open pilot trial, R-salbutamol sulphate, a well-known molecule with anti-inflammatory effects, was tested successfully on patients with therapy-resistant discoid lupus erythematosus (DLE).

OBJECTIVES

To compare the efficacy and safety of R-salbutamol cream 0.5% vs. placebo on DLE lesions in a multicentre, double-blinded, randomized, placebo-controlled phase II trial.

METHODS

Thirty-seven patients with at least one newly developed DLE lesion were randomized - 19 to the R-salbutamol cream 0.5% and 18 to placebo - and treated twice daily for 8 weeks. Efficacy was evaluated through scores of erythema, scaling/hypertrophy and induration as well as pain and itching; general improvement scored by the investigator and global improvement scored by patients' assessment were also evaluated.

RESULTS

The mean area under the curve of improvement for scaling/hypertrophy, pain, itching and global patient assessment was significantly better for the actively treated patients as compared with placebo (scaling/hypertrophy, P = 0.0262; pain, P = 0.0238; itching, P = 0.0135; global patient assessment, P = 0.045). Moreover, the percentage of patients without induration was significantly higher in the active group compared with the placebo group (P = 0.013), and a statistically significantly greater decrease in the size of the lesional area was also seen in the overall analysis of the R-salbutamol-treated patients (P = 0.0197). No serious adverse events were reported.

CONCLUSIONS

Application of R-salbutamol cream 0.5% was safe and well tolerated. Statistically significant effects were seen on scaling/hypertrophy, induration, pain and itching as well as patient global assessment, suggesting that R-salbutamol could be a promising new topical therapy alternative for DLE.

Long-term safety study of levalbuterol administered via metered-dose inhaler in patients with asthma

BACKGROUND

Previous studies have raised concerns regarding the safety of regular use of beta2-agonists for treating asthma. Few studies have explored the safety of at least 1 year of use of racemic albuterol, and none have examined long-term dosing of levalbuterol.

OBJECTIVE

To examine the long-term safety of levalbuterol hydrofluoroalkane (HFA) vs racemic albuterol HFA administered via metered-dose inhaler (MDI) in patients with stable asthma.

METHODS

Patients with mild to moderate asthma (mean forced expiratory volume in 1 second [FEVI], 68.3% of predicted) 12 years or older participated in a multicenter, parallel-group, open-label study. Patients were randomized to levalbuterol HFA MDI (90 microg; 2 actuations of 45 microg; n = 496) or racemic albuterol HFA MDI (180 microg; 2 actuations of 90 microg; n = 250) for 52 weeks of 4 times daily dosing. The primary end point was the incidence of postrandomization adverse events. Asthma exacerbations and pulmonary parameters were also assessed.

RESULTS

The overall incidence of adverse events was similar for levalbuterol (72.0%) and racemic albuterol (76.8%). Rates of beta-mediated adverse events, serious adverse events, and discontinuations because of adverse events were low (<15%) and were comparable between groups. Rates of asthma adverse events for levalbuterol and racemic albuterol were 18.3% and 19.6%, respectively. Mean percentage of predicted FEV1 improved after dosing and was stable for both groups.

CONCLUSION

In this trial, up to 52 weeks of regular use of levalbuterol HFA MDI or racemic albuterol HFA MDI was well tolerated, and no deterioration of lung function was detected during the study period.

(R)-albuterol decreases immune responses: role of activated T cells

Racemic albuterol is an equimolar mixture of two isomers, (R) and (S). Whether (R) and (S) isomers and the combination of both exert different effects in immune activation is not well defined. We analyzed the effects of (R+S)-albuterol, (R)-albuterol and (S)-albuterol in a murine model of allergic pulmonary inflammation and in activated T cells. Mice (C57BL/6) sensitized and aerosol challenged with the allergen ovalbumin (OVA) or phosphate buffered saline (PBS) were treated with (R)-albuterol, (S)-albuterol or (R+S)-albuterol. Following administration of (R)-albuterol, allergen induced bronchoalveolar lavage eosinophils and IgE showed a decrease, albeit not significantly by ANOVA. As T cells are important in allergic inflammation, we asked whether (R+S), (R) or (S)-albuterol might differ in effects on T cells and on the activity of the inflammatory transcription factor NF-κB. In activated T cells, (R)-albuterol administration decreased levels of inflammatory cytokines and NF-κB activity. These studies suggest that (R)-albuterol decreases cytokine secretion and NF-κB activity in T cells.

Role of arformoterol in the management of COPD

Formoterol is a beta2-agonist that has both short and long acting bronchodilator effects. Beta2-agonists used as bronchodilators have been synthesized as racemates that comprise (R,R) and (S,S)-enantiomers. Compounds that are beta2-selective derive their bronchodilator effect from an interaction between the (R,R)-enantiomer and the beta2-adrenoceptor. Arformoterol is the (R,R)-enantiomer and is distinguished from the more commonly used racemic (RR/S,S)-diasteriomer of formoterol. Overall literature on the use of arformoterol in COPD is very preliminary. There is some in vitro data that demonstrate significant bronchodilation and inhibition of inflammation with arformoterol, and these effects may be more pronounced than those caused by racemic formoterol. There are limited clinical trial data that demonstrate that arformoterol produces significant improvement in lung function in COPD; however, many of the subjects involved had marked baseline airway reversibility. Arformoterol has been very well tolerated in clinical trials and could potentially be used only once every 24 hours (due to its prolonged effect). It can only be given in nebulized form. Arformoterol can potentially be given with other inhaled medications.

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.

Beta2-agonists and bronchial hyperresponsiveness

Bronchial hyperresponsiveness (BHR) is a characteristic feature of asthma, and individuals with this disease respond to a range of physiological and chemical insults that are otherwise innocuous to healthy subjects, suggesting that the mechanisms underlying this phenomenon are characteristic of the asthma phenotype. BHR can be increased following exposure to environmental allergens in suitably sensitized individuals, pollutants, and certain viruses and can also be exacerbated by exposure to certain drugs, including nonsteroidal anti-inflammatory agents and beta-blockers. Although beta2-agonists administered acutely remain the treatment for the symptoms of asthma, paradoxically, regular treatment with these drugs can result in an increase in BHR, and this has been suggested to contribute to the increase in asthma morbidity and mortality that has been reported by numerous investigators. This article highlights our current understanding of this phenomenon and examines the potential mechanisms responsible for this effect.

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

BACKGROUND

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

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?"

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.

Continuous nebulized albuterol attenuates acute lung injury in an ovine model of combined burn and smoke inhalation

OBJECTIVE

Albuterol, due to its bronchodilatory and anti-inflammatory effects, is given via continuous nebulization in children with severe asthma. Combined burn and smoke inhalation injury frequently results in acute lung injury due to a combination of airway obstruction and inflammation. We hypothesized that albuterol administered via continuous nebulization would mitigate acute lung injury after smoke inhalation injury and burn.

DESIGN

Randomized prospective animal model.

SUBJECTS

Twenty adult female sheep (mean weight, 33.1+/-0.9 kg).

INTERVENTIONS

Adult ewes were subjected to a 40% body surface area third-degree flame burn and smoke inhalation injury after tracheostomy. Sheep were allocated to a) sham group, b) saline continuous nebulization group, c) 20 mg of albuterol continuous nebulization group, or d) 40 mg of albuterol continuous nebulization group (n=5 animals per group). All groups received intravenous lactated Ringer's solution at 4 mL.kg-1.%burn(-1).24 hrs-1 for resuscitation and were equally mechanically ventilated throughout the 48-hr study period. Pulmonary and cardiac function, lung lymph flow, bronchial obstruction score, and wet/dry lung weights were recorded.

RESULTS

Compared with saline and control groups, the albuterol groups had lower pause and peak inspiratory pressures, decreased pulmonary transvascular fluid flux, a significantly higher Pao2/Fio2 ratio, and decreased shunt fraction at 48 hrs postinjury. The wet-to-dry lung weight ratio and bronchial obstruction scores were lower for sheep receiving albuterol.

CONCLUSIONS

Continuous nebulization of albuterol improves pulmonary function via improved airway clearance and decreased fluid flux in a combined burn/smoke inhalation injury model.

Evaluation of levalbuterol metered dose inhaler in pediatric patients with asthma: a double-blind, randomized, placebo- and active-controlled trial

OBJECTIVE

To evaluate the efficacy and safety of levalbuterol metered dose inhaler (MDI) in children aged 4-11 years (n = 173).

RESEARCH DESIGN AND METHODS

Multicenter, randomized, double-blind 28-day study of QID levalbuterol 90 microg, racemic albuterol 180 mug, and placebo (2:1:1 ratio). Serial spirometry was performed on Days 0, 14, and 28. The primary endpoint was the double-blind average peak percent (%) change in FEV(1) from visit pre-dose; the primary comparison was with placebo. Secondary endpoints included the area under the FEV(1) percent change from pre-dose curve and peak % predicted FEV(1). Safety endpoints included adverse events, laboratory tests, rescue medication use, and electrocardiograms.

RESULTS

Levalbuterol significantly improved the least square mean peak percent change in FEV(1) compared with placebo (levalbuterol 25.6% +/- 1.3% [p < 0.001]; racemic albuterol 21.8% +/- 1.8% [p = ns]; placebo 16.8% +/- 1.9%). Results for levalbuterol were similar for the other spirometry endpoints (p < 0.05 vs. placebo). No levalbuterol-treated patients had a peak percent change in FEV(1) < 10% (compared with 15.8% of racemic albuterol-treated patients and 30.3% of placebo-treated patients). The incidence of adverse events was 43.4% for levalbuterol, 56.4% for racemic albuterol, and 51.4% for placebo. The rate of discontinuation was 1.3% for levalbuterol, 2.6% for racemic albuterol, and 8.6% for placebo. The rate of asthma attacks (10.5%, 12.8%, 14.3%, respectively) was similar among treatments. Levalbuterol and racemic albuterol both reduced rescue medication use (p < 0.01 vs. placebo) and produced changes in ventricular heart rate and QT(c-F) that were similar to placebo.

CONCLUSIONS

In this study, levalbuterol administered via MDI significantly improved airway function in comparison with placebo in asthmatic children aged 4-11 years with a safety profile that was similar to placebo.

Population pharmacokinetics of (R)-albuterol and (S)-albuterol in pediatric patients aged 4-11 years with asthma

OBJECTIVE

To characterize the population pharmacokinetics (PK) of (R)- and (S)-albuterol in pediatric asthmatics using a model that supports a sparse blood sampling strategy.

METHODS

The data for this analysis were collected from patients enrolled in a randomized, double-blind, multicenter, placebo- and active-controlled study evaluating the safety and efficacy of levalbuterol in asthmatic children aged 4-11 years. Patients received either levalbuterol 0.31 mg, levalbuterol 0.63 mg, racemic albuterol 1.25 mg, or racemic albuterol 2.5 mg via nebulizer. Separate population pharmacokinetic models were developed for (R)- and (S)-albuterol using the NOMNEM((R)) computer program. Covariate models were developed to identify significant predictors of inter-patient variability.

RESULTS

A total of 995 samples and 262 patients were used for the (R)-albuterol population PK model while a total of 496 samples and 128 patients were used for the (S)-albuterol population PK model. The apparent clearance of (R)-albuterol was much more rapid than that of (S)-albuterol (approximately four-fold higher), and the apparent volume of distribution was much larger for (R)-albuterol (in part due to pre-systemic metabolism) than for (S)-albuterol (approximately four-fold higher).

CONCLUSIONS

In this study of pediatric patients, the models were able to demonstrate using two to four samples per patient that the apparent clearance and volume of distribution of (R)-albuterol were several fold higher than that of (S)-albuterol. The pharmacokinetics of (R)-albuterol were similar after administration of levalbuterol or racemic albuterol and were linear over the examined dose range (0.31-0.63 mg nebulized dose). The presence of (S)-albuterol did not significantly alter the pharmacokinetics of (R)-albuterol, suggesting that effects of (S)-albuterol may be due to the intrinsic pharmacology of this isomer.

Effects of (R)- and (S)-isomers of beta-adrenergic agonists on eosinophil response to interleukin-5

BACKGROUND

Racemic beta2-adrenergic receptor agonists (beta2-agonists) are used frequently to treat patients with asthma. Potential differences in the biological activities and clinical efficacies among racemic beta2-agonists and their isomers are controversial, and research into these possible differences is limited.

OBJECTIVE

We hypothesized that the (S)- and the (R)-isomers of beta2-agonists have opposing effects on the activation of inflammatory cells.

METHODS

Isolated human eosinophils were pretreated with 1:1 racemic (R,S)-, (R)- or (S)-albuterol, isobutyl methylxanthine (IBMX), and stimulated with IL-5. The kinetics of superoxide production were examined by reduction of cytochrome c, and the effects of pharmacological agents on superoxide production were monitored for 180 min.

RESULTS

(R,S)-albuterol inhibited IL-5-induced superoxide production. This inhibition was enhanced by a cyclic adenosine monophosphate (cAMP) phosphodiesterase inhibitor, IBMX, and was reversed by the selective beta2-adrenergic receptor antagonist, ICI 118, 551, verifying the involvement of both cAMP and the beta2-adrenergic receptor. In addition, (R)-albuterol alone, similarly to (R,S)-albuterol, significantly inhibited IL-5-induced superoxide production up to 60 min (P<0.05, n=4), but the inhibition was lost with longer incubation. In contrast, (S)-albuterol with IBMX did not inhibit IL-5-induced superoxide production before 60 min, but it significantly enhanced IL-5-mediated superoxide production after 60 min (P<0.05, n=4). When both were present as racemic (R,S)-albuterol, the inhibitory effect of (R)-albuterol was not affected by (S)-albuterol.

CONCLUSION

When incubated with IL-5-activated eosinophils, (R)-albuterol shows anti-inflammatory effects and (S)-albuterol shows pro-inflammatory effects in the presence of IBMX. The kinetics of these effects are different, and when used simultaneously, (R)-albuterol predominates. When marked usage of the (S)-isomer is anticipated, racemic (R,S)-albuterol should be used clinically with caution.

Levalbuterol inhibits human airway smooth muscle cell proliferation: therapeutic implications in the management of asthma

BACKGROUND

Racemic albuterol is a mixture of (R)- and (S)-enantiomers of albuterol. Its pharmacological activity and clinical efficacy reside in the (R)-enantiomer (levalbuterol), but the (S)-enantiomer exacerbates airway reactivity in nonclinical models. The role of albuterols in airway smooth muscle cell (SMC) proliferation is not well understood.

METHODS

The effect of levalbuterol on human bronchial SMC growth was compared with the effects of racemic albuterol and (S)-albuterol. Cells were fed albuterols and 3H-thymidine in 5% FBS and incubated for 24 h. The effect of (S)-albuterol on levalbuterol actions was also studied and so were the effects of cAMP/PKA, PI-3 kinase, NK-kappaB, and retinoblastoma (Rb) proteins on albuterols and human bronchial SMC proliferation.

RESULTS

Levalbuterol inhibited cell proliferation at low concentrations. The growth-inhibitory effect of levalbuterol occurs via activation of the cAMP/PKA pathway. Addition of (S)-albuterol to levalbuterol decreased the growth-inhibitory effect of levalbuterol, and (S)-albuterol attenuated levalbuterol-induced cAMP release by 65%. Levalbuterol inhibited NF-kappaB and Rb protein expressions. ICI-118551 abrogated the inhibitory properties of levalbuterol. The PAF receptor antagonist CV-3988 inhibited (S)-albuterol-induced cell growth, with no effect on levalbuterol.

CONCLUSIONS

Levalbuterol inhibits cell growth by activating the cAMP/PKA pathway and inhibiting PI-3 kinase, NF-kappaB and Rb protein expression, and (S)-albuterol induces cell growth by activating PAF-receptor-mediated cell signaling.

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.

Randomized placebo controlled assessment of airway inflammation due to racemic albuterol and levalbuterol via exhaled nitric oxide testing

STUDY OBJECTIVES

The S-stereoisomer found in racemic albuterol may have associated proinflammatory properties. We tested the hypothesis that airway inflammation as assessed by exhaled nitric oxide is no different in patients with COPD when using racemic albuterol relative to levalbuterol or placebo.

MEASUREMENTS

Twelve mild to moderate COPD patients were assigned to five days each of nebulized racemic albuterol, levalbuterol, and saline placebo. Before and after each course of treatment, airway inflammation was assessed via exhaled nitric oxide breath testing. Secondary functional outcomes that were measured included spirometry, a functional assessment utilizing a six-minute walk, and symptoms score using the University of California, San Diego Shortness of Breath Questionnaire.

RESULTS

There was no statistically significant difference in pre and post FeNO levels within and between treatment groups (p = 0.121). There were also no significant differences within or between treatment groups for the secondary outcome measurements of FEV1 (p = 0.913), functional assessment utilizing a six-minute walk (p = 0.838) and the symptom scores using Shortness of Breath Questionnaire (p = 0.500).

CONCLUSION

We found no difference in mild to moderate COPD patients treated with racemic albuterol, levalbuterol or placebo for measurement of exhaled nitric oxide or the secondary outcomes that were measured.

(R)-albuterol elicits antiinflammatory effects in human airway epithelial cells via iNOS

Catecholamines can suppress production of inflammatory mediators in different cell types, including airway epithelium, but downstream signaling mechanisms involved in regulation of these antiinflammatory effects are largely unknown. We theorized that acute beta2-adrenergic stimulation of airway epithelial cells with albuterol could suppress the production and release of inflammatory mediators, specifically granulocyte macrophage-colony stimulating factor (GM-CSF) via a pathway involving inducible nitric oxide synthase (iNOS). Normal human bronchial epithelial (NHBE) cells in primary culture were exposed to a cytokine mixture (10 ng/ml each IFN-gamma and IL-1beta) to induce iNOS expression. (R)- and (S)-enantiomers of albuterol, as well as racemic mixtures, were added with these cytokines, and effects on GM-CSF expression and production were assessed. Specific inhibitors and activators of protein kinases (PKs), beta2-adrenergic receptor antagonists, and small interfering RNAs against iNOS were used to delineate signaling pathways involved. iNOS message was significantly upregulated in a concentration-dependent manner by the active (R)-enantiomer of albuterol. (R)-albuterol also attenuated cytokine-induced increases in GM-CSF steady-state mRNA expression and protein release. The (S)-enantomer of albuterol had no effect on these parameters. PKC, specifically, the delta isoform, was required for iNOS message increase, but PKA and PKG were not involved in the pathway. Overall, this study identifies a novel pathway by which beta2-adrenergic agonists may exhibit antiinflammatory effects in airway epithelium and surrounding milieu.

Advances in the management of pediatric asthma: a review of recent FDA drug approvals and label updates

Children have the highest prevalence of asthma of any age group. In the United States during 2001, there were 12.6 million physician and hospital outpatient visits for asthma treatment, of which almost 5 million involved children 18 years and younger. Therapeutic advances in pediatric asthma could improve patient outcomes and potentially reduce the burden on health care systems. Efforts to obtain efficacy and safety data in pediatric populations and develop pediatric formulations of asthma treatments have been encouraged by the FDA and clinicians. This article reviews the newest additions to asthma therapies approved for use in children, including an inhaled corticosteroid, some long-acting beta2-agonists, some leukotriene-receptor blockers, and a single-isomer, short-acting beta2-agonist.

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.

Differential control of TH1 versus TH2 cell responses by the combination of low-dose steroids with beta2-adrenergic agonists

BACKGROUND

Combination treatment with steroids and long-acting beta2-agonists provides greater asthma control than simply increasing the dose of steroids.

OBJECTIVE

Although the effects of combination treatment with steroids and long-acting beta2-agonists have been attributed to their anti-inflammatory and bronchodilator effects, the ability of this combination to act synergistically on T cells has not been explored.

METHODS

PBMCs from control subjects and allergic asthmatic patients were stimulated with PHA in the presence of low doses of fluticasone propionate (FP) with or without salmeterol for 72 hours. The inhibition of T-cell proliferation, cytokine production, and glucocorticoid receptor translocation was measured.

RESULTS

Both groups showed a similar degree of inhibition of PHA-induced T-cell proliferation with FP (inhibitory concentration of 50% approximately 10(-9) mol/L) alone. Use of lower concentrations of FP (10(-12) to 10(-11) mol/L) in combination with salmeterol (10(-10) to 10(-7) mol/L) in control subjects provided similar inhibition of proliferation. This combination treatment was associated with significantly greater glucocorticoid receptor translocation into the cell nucleus compared with that seen with FP alone (10(-12) mol/L; P <.01). In contrast, FP-salmeterol failed to act synergistically in asthmatic patients. The 2-drug combination significantly inhibited production of TNF-alpha and IFN-gamma in both groups (P <.05) but failed to inhibit TH2 cytokine (IL-5 and IL-13) production by PBMCs from asthmatic patients. Because allergic inflammation is associated with increased levels of cellular phosphodiesterases that might degrade salmeterol-induced cyclic adenosine monophosphate, rolipram (10(-6) mol/L), a phosphodiesterase 4 inhibitor, was added to the FP-salmeterol combination. This triple combination of drugs enhanced inhibitory activity of low-dose steroids on T-cell proliferation in asthmatic patients and inhibited IL-13 production.

CONCLUSION

These data suggest that beta2-agonists in combination with low doses of steroids can suppress T-cell proliferation and TH1 cytokine production from healthy individuals, but suppression of T cells with a combination of FP and salmeterol in asthmatic patients requires inhibition of phosphodiesterases.

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.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

This was a prospective, open-label, nonrandomized pilot study to evaluate efficacy and tolerability of levalbuterol (LEV) in acute asthma. Asthmatics (forced expiratory volume in 1 second [FEV1], 20-55% predicted) were sequentially enrolled into cohorts of 12 to 14 and received 0.63, 1.25, 2.5, 3.75, or 5.0 mg LEV or 2.5 or 5.0 mg racemic albuterol (RAC) every 20 minutes x 3. After the first dose, FEV1 changes were 56% (0.6 L) for 1.25 mg LEV and 6% (0.07 L) and 14% (0.21 L) for 2.5 and 5 mg RAC respectively. After three doses, FEV1 changes were 74% (0.9 L), 39% (0.5 L), and 37% (0.6 L) for 1.25 mg, LEV 2.5 mg, RAC and 0.63 mg LEV respectively. LEV doses greater than 1.25 mg did not further improve bronchodilation. Baseline plasma (S)-albuterol levels were negatively correlated with baseline FEV1 (R = - 0.3, P = .004) and percent change in FEV1 (R = -0.3, P = .006). LEV at a dose of 1.25 mg produced effective bronchodilation that was greater than both RAC doses. The negative correlation between (S)-albuterol levels and FEV1 could suggest a deleterious effect of (S)-albuterol. Larger comparative studies are warranted.