Differential effect of formoterol on adenosine monophosphate and histamine reactivity in asthma

Influence of beta2-adrenoceptor gene polymorphisms on beta2-adrenoceptor expression in human lung

BACKGROUND

The aim of the present study was to establish whether polymorphisms, especially those within the promoter region, of the beta(2)-adrenoceptor gene (ADRB2) influence beta(2)-adrenoceptor expression in human lung.

METHODS

The density of beta-adrenoceptors in human lung tissue (n=88) was determined by saturation binding using the radioligand, iodinated cyanopindolol. Discrimination of beta(1)- and beta(2)-adrenoceptors was determined using the highly selective beta(1)-adrenoceptor antagonist, CGP20712A. Genotype was determined at 5 positions of ADRB2 previously reported as polymorphic. Potential influences of single nucleotide polymorphisms (SNPs) within the promoter region (-367, -47) and coding block (46, 79, 491) of ADRB2 on beta(2)-adrenoceptor expression were investigated.

RESULTS

The density of beta(2)-adrenoceptors was variable among the 88 lung preparations studied ranging from 17 to 177fmol/mg protein (mean+/-S.E.M., 72+/-4fmol/mg protein). There was no influence of genotype on beta(2)-adrenoceptor expression for any of the polymorphisms studied except at position 491. The polymorphism at position 491C>T, leading to a change from thr to ile at amino acid 164, is uncommon. Preparations genotyped as heterozygous (126+/-15fmol/mg protein; n=5) expressed significantly (P=0.0005) higher levels of beta(2)-adrenoceptor than those that were homozygous (69+/-4fmol/mg protein; n=83).

CONCLUSION

With the exception of position 491, these data indicate that polymorphisms of ADRB2 do not influence beta(2)-adrenoceptor expression in human lung.

Time to death and mast cell degranulation in fatal asthma

BACKGROUND AND OBJECTIVE

Attacks of fatal asthma have been shown to be either of short duration or long duration and associated with differing degrees of smooth muscle contraction, luminal mucus deposition and ratios of eosinophils to neutrophils in the airway wall. We hypothesized that this bimodal distribution might be related to airway mast cell degranulation.

METHODS

Airway sections from cases of fatal asthma in the second Victorian asthma mortality study and from cases coming to coronial autopsy in Perth were examined. Tryptase-positive mast cells, numbers of intact and degranulated mast cells, post-mortem blood salbutamol levels and airway dimensions were measured.

RESULTS

Although the total number of mast cells were similar, the ratio of degranulated to intact mast cells (D/I) was significantly increased in the smooth muscle (P < 0.05) and outer airway wall (P < 0.001), in short-duration cases compared with long-duration cases. Proportional muscle shortening was significantly increased (P < 0.05) in short-duration cases (17 +/- 7%) compared with long-duration cases (11 +/- 7%). Blood salbutamol levels were related to the total airway wall mast cell D/I ratio for all cases combined (r = 0.57, P = 0.01).

CONCLUSIONS

The duration of a fatal attack of asthma may be partly determined by the degranulation of mast cells.

The long-acting beta-adrenoceptor agonist, indacaterol, inhibits IgE-dependent responses of human lung mast cells

BACKGROUND AND PURPOSE

The long-acting beta(2)-adrenoceptor agonist, indacaterol, has been developed as a bronchodilator for the therapeutic management of respiratory diseases. The aim of the present study was to determine whether indacaterol has any anti-inflammatory activity. To this end, the effects of indacaterol on human lung mast cell responses were investigated.

EXPERIMENTAL APPROACH

The effects of indacaterol, and the alternative long-acting beta-agonists formoterol and salmeterol, were investigated on the IgE-dependent release and generation of histamine, cysteinyl-leukotrienes and prostaglandin D(2) from human lung mast cells. Moreover, the extent to which long-term (24-72 h) incubation of mast cells with long-acting beta-agonists impaired the subsequent ability of beta-agonists to inhibit mast cell responses was assessed.

KEY RESULTS

Indacaterol was as potent and as efficacious as the full agonist, isoprenaline (EC(50), approximately 4 nmol x L(-1)), at inhibiting the IgE-dependent release of histamine from mast cells. Formoterol was a full agonist whereas salmeterol was a partial agonist as inhibitors of histamine release. All three long-acting beta-agonists were effective inhibitors of the IgE-dependent generation of cysteinyl-leukotrienes and prostaglandin D(2). Long-term incubation of mast cells with long-acting beta-agonists led to a reduction in the subsequent ability of beta-agonists to stabilize mast cell responses. This tendency to induce functional desensitization was least evident for indacaterol.

CONCLUSIONS AND IMPLICATIONS

Indacaterol is an effective inhibitor of the release of mediators from human lung mast cells. This suggests that, as well as bronchodilation, mast cell stabilization may constitute an additional therapeutic benefit of indacaterol.

Adenosine receptors and asthma

The accumulation of evidence implicating a role for adenosine in the pathogenesis of asthma has led to investigations into all adenosine receptor subtypes as potential therapeutic targets for the treatment of asthma. Selective A(1) receptor antagonists are currently in preclinical development since adenosine has been shown experimentally to mediate various features of asthma through this receptor such as bronchoconstriction, mucus secretion and inflammation. The A(2A) receptor is expressed on most inflammatory cells implicated in asthma, and as A(2A) stimulation activates adenylate cyclase and consequently elevates cAMP, selective A(2A) receptor agonists have now reached clinical development. However, initial reports concerning their efficacy are inconclusive. A(2B) receptor antagonists are also under investigation based on the rationale that inhibiting the effects of adenosine on mast cells would be beneficial, in addition to other reported pro-inflammatory effects mediated by the A(2B) receptor on cells such as airway smooth muscle, epithelial cells and fibroblasts. Whilst the effects in pre-clinical models are promising, their efficacy in the clinical setting has also yet to be reported. Finally, adenosine A(3) receptor stimulation has been demonstrated to mediate inhibitory effects on eosinophils since it also elevates cAMP. However, some experimental reports suggest that A(3) antagonists mediate anti-inflammatory effects, thus the rationale for A(3) receptor ligands as therapeutic agents remains to be determined. In conclusion, establishing the precise role of adenosine in the pathogenesis of asthma and developing appropriate subtype selective agonists/antagonists represents an exciting opportunity for the development of novel therapeutics for the treatment of asthma.

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.

Influence of beta2-adrenoceptor gene polymorphisms on beta2-adrenoceptor-mediated responses in human lung mast cells

BACKGROUND AND PURPOSE

Previous studies have shown that beta(2)-adrenoceptor-mediated responses in human lung mast cells are highly variable. The aims of the present study were to establish whether polymorphisms of the beta (2)-adrenoceptor gene (ADRB2) influence this variability in (a) beta(2)-adrenoceptor-mediated inhibition and (b) desensitization of beta(2)-adrenoceptor-mediated responses in human lung mast cells.

EXPERIMENTAL APPROACH

Mast cells were isolated from human lung tissue. The inhibitory effects of the beta-adrenoceptor agonist, isoprenaline (10(-10)-10(-5) M), on IgE-mediated histamine release from mast cells were determined (n=92). Moreover, the inhibitory effects of isoprenaline were evaluated following a desensitizing treatment involving long-term (24 h) incubation of mast cells with isoprenaline (10(-6) M) (n=65). A potential influence of polymorphisms on these functional responses was determined by genotyping 11 positions, in the promoter and coding regions, of ADRB2 previously reported as polymorphic.

KEY RESULTS

There was no influence of any of the polymorphic positions of ADRB2 on the potency of isoprenaline to inhibit histamine release from mast cells with the exception of position 491C>T (Thr164Ile). There was no influence of any of the polymorphic positions of ADRB2 on the extent of desensitization of the isoprenaline-mediated response following a desensitizing treatment except for position 46G>A (Gly16Arg). Analyses at the haplotype level indicated that there was no influence of haplotype on beta (2)-adrenoceptor-mediated responses in mast cells.

CONCLUSIONS AND IMPLICATIONS

These data indicate that certain polymorphisms in ADRB2 influence beta(2)-adrenoceptor-mediated responses in human lung mast cells.

Regulation of mast cells by beta-agonists

The human lung mast cell is known to be a critical effector cell in the mediation of asthma. Activation of the mast cell by allergens and other stimuli leads to the release and generation of a wide variety of autacoids that cause bronchoconstriction, promote inflammation, and may influence airway remodeling. Therefore, the stabilization of mast cells has obvious value in the prevention of asthma. Among the drugs used to treat asthma, only beta-agonists are effective stabilizers of mast cells. Both short- and long-acting beta-agonists are effective against mast cells, but there are differences between agonists regarding the extent of inhibitory activity attained. Consequently, the type of beta-agonist prescribed influences the degree of mast cell stabilization possible. Despite the potential value of attenuating mast cell activity with beta-agonists, this benefit may diminish with time because of the development of tolerance. Both short- and long-acting beta-agonists can induce tolerance to mast cell stabilization, and generally, higher efficacy agonists tend to induce greater levels of tolerance; however, weaker agonists induce greater levels of tolerance than might be expected. Tolerance to the mast-cell-stabilizing effects of beta- agonists may be an issue clinically, because this occurs more readily than tolerance to smooth muscle relaxation. This could lead to a situation in which beta-agonists fail to prevent the release of mediators from mast cells but can still effectively relax airway smooth muscle. The continued ability to bronchodilate could mask the unfavorable consequences of unchecked mediator release from mast cells.

Current issues with beta2-adrenoceptor agonists: pharmacology and molecular and cellular mechanisms

Beta2-adrenoceptors are widely, almost ubiquitously, expressed. Activation of these receptors on bronchial smooth muscle by short- and long-acting beta2-adrenoceptor agonists causes bronchodilation. Here, the beta2-adrenoceptor is linked by the G protein, Gs, to adenylyl cyclase, which increases cyclic adenosine monophosphate (cAMP), thus activating protein kinase A, which affects calcium levels and reduces the efficiency of myosin light-chain kinase, causing relaxation. Activation also entrains numerous acute and longer term downregulation responses affecting the number, location, and net efficiency of signaling of the receptor. Synthetic beta2-agonists are all "partial agonists," incompletely able to optimally stimulate cAMP signal transduction. However, compared with some cells (such as mast cells) involved in exercise- induced asthma induction, airway smooth muscle is privileged in that transduction efficiency is intrinsically high and the tissue is very resistant to complete downregulation. Glucocorticosteroids have broadly beneficial interactions with beta2-adrenoceptors. Researchers have recently discovered that the beta2-adrenoceptor may function as a homodimer and that it can form heterodimers with both the beta1- and beta3-adrenoceptors, and possibly other receptors. This further complicates interpretation of the effect of beta2-adrenoceptor polymorphisms, but it is unknown whether this occurs in humans in vivo. Researchers have known for some time that strong contraction involving receptors coupled to the Gq G protein (e.g., cholinergic and leukotriene receptors via negative biochemical crosstalk), virus infection (via uncoupling), and inflammation (via kinases) can impair relaxation. Most recently, researchers have discovered that the beta2-adrenoceptor can also send potentially adverse signals after "atypical coupling" to Gq rather than Gs. The clinical implications of these uncouplings, crosstalk, and atypical coupling possibilities are not well-understood.

The effects of inhaled budesonide and formoterol in combination and alone when given directly after allergen challenge

BACKGROUND

The use of combination inhaled budesonide and formoterol as maintenance and reliever therapy significantly improves the risk and the time to exacerbations in asthma.

OBJECTIVES

To explore the mechanisms underlying the effect of the reliever dose on exacerbations by examining the effect of combination therapy on the allergen challenge model when given after allergen exposure.

METHODS

In a randomized, double-blind crossover study, single doses of budesonide/formoterol (400/12 mug), formoterol (12 mug), budesonide (400 mug), or placebo were administered during the acute bronchoconstriction response (early airway response) immediately after allergen inhalation in 15 patients with mild asthma. Allergen-induced late airway response (LAR), sputum inflammatory markers, airway hyperresponsiveness, and exhaled nitric oxide were measured.

RESULTS

All active treatments significantly attenuated the LAR, with budesonide/formoterol significantly better than its monocomponents (maximum FEV(1) fall: placebo, [mean +/- SEM] 21.2% +/- 3.1%; budesonide/formoterol, 4.2% +/- 1.4%; formoterol, 7.5% +/- 1.7%; budesonide, 10.4% +/- 1.6%). Allergen-induced change in methacholine PC(20) was significantly attenuated by budesonide/formoterol, but not by its monocomponents. Sputum cell counts and exhaled nitric oxide increased significantly after all allergen challenges, with no significant attenuation by any of the treatments. Therapy with combination and formoterol alone, but not budesonide, significantly reduced the early airway response.

CONCLUSION

A single dose of budesonide/formoterol was superior to its monocomponents in attenuating the allergen-induced LAR and airway hyperresponsiveness. These effects may represent the contribution of the reliever dose to the budesonide/formoterol maintenance and reliever regimen.

CLINICAL IMPLICATIONS

The protective effect against allergic airway responses with a single reliever dose of budesonide/formoterol is predominantly related to greater functional antagonism of airway smooth muscles.

Beta-adrenoceptor responses of the airways: for better or worse?

Beta2-adrenoceptor agonists are the first-line treatment of asthma and chronic obstructive pulmonary disease (COPD), in which a short-acting beta2-adrenoceptor agonist is used as required for relief of bronchoconstriction. A long-acting beta2-adrenoceptor agonist may be added to an inhaled corticosteroid as step 3 in the management of chronic asthma. Long-acting beta2-adrenoceptor agonists may also be added in treatment of COPD. This review examines the beneficial and detrimental effects of beta2-adrenoceptor agonists. The beneficial effects of beta2-adrenoceptor agonists are mainly derived from their bronchodilator activity which relieves the bronchiolar narrowing and improves air flow. The potential anti-inflammatory actions of stabilizing mast cell degranulation and release of inflammatory and bronchoconstrictor mediators, is considered. Other potential beneficial responses include improvements in mucociliary clearance and inhibition of extravasation of plasma proteins that is involved in oedema formation in asthma. The side effects of beta2-adrenoceptor agonists are primarily related to beta2-adrenoceptor-mediated responses at sites outside the airways. Of major concern has been the development of tolerance and this is discussed in relation to incidence of increased morbidity and mortality to asthma over the past three decades. A clinical aspect of beta2-adrenoceptor pharmacology in recent years has been the recognition of genetic polymorphism of the receptor and how this affects responses to and tolerance to beta2-adrenoceptor agonists. A controversial feature of beta2-adrenoceptor agonists is their stereoisomerism and whether the inactive (S)-isomer of salbutamol had detrimental actions in the commercially used racemate. The consensus is that despite these adverse properties, beta2-adrenoceptor agonist remains the most useful pharmacological agents in the management of asthma and COPD.

Investigative bronchoprovocation and bronchoscopy in airway diseases

RATIONALE

Basic and clinical research strategies used for many lung diseases have depended on volunteer subjects undergoing bronchoscopy to establish access to the airways to collect biological specimens and tissue, perhaps with added bronchoprovocation in asthma syndromes. These procedures have yielded a wealth of important scientific information. Since the last critical review more than a decade ago, some of the techniques and applications have changed, and untoward events have occurred, raising safety concerns and increasing institutional review scrutiny.

OBJECTIVES AND METHODS

To reappraise these investigational methods in the context of current knowledge, the National Heart, Lung, and Blood Institute and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health convened a working group to review these procedures used for airway disease research, emphasizing asthma and chronic obstructive pulmonary disease.

MAIN RESULTS

The group reaffirmed the scientific importance of investigative bronchoscopy and bronchoprovocation, even as less invasive technologies evolve. The group also considered the safety of bronchoscopy and bronchoprovocation with methacholine and antigen to be acceptable for volunteer subjects and patients, but stressed the need to monitor this closely and to emphasize proper training of participating medical research personnel. Issues were raised about vulnerable volunteers, especially children who need surrogates for informed consent.

CONCLUSION

This review of investigative bronchoscopy and bronchoprovocation could serve as the basis for future guidelines for the use of these procedures in the United States.

Long-acting beta2-agonists: comparative pharmacology and clinical outcomes

Salmeterol and formoterol are both long-acting beta(2)-adrenoceptor agonists (beta(2)-agonists). They both provide excellent bronchodilating and bronchoprotective effects in patients with asthma but their are some differences between these two long-acting beta(2)-agonists in vitro and in vivo. Formoterol has a greater potency and intrinsic activity than salmeterol, which can become especially apparent at higher doses than that clinically recommended, and in contracted bronchi. Long-term use of long-acting beta(2)-agonists can induce tolerance, which can be partially reversed with corticosteroids. Long-acting beta(2)-agonists have some anti-inflammatory effects in vitro, but data in vivo are less convincing. Compared with doubling the dose of inhaled corticosteroids, the addition of inhaled long-acting beta(2)-agonists to inhaled corticosteroids improves symptom control in patients with asthma and reduces both the exacerbation rate of asthma and hospital admission rate. No enhanced airway responsiveness or loss of perception of dyspnea has been observed with the use of inhaled long-acting beta(2)-agonists. Monotherapy with long-acting beta(2)-agonists is not recommended.

Add-on therapy with montelukast or formoterol in patients with the glycine-16 beta2-receptor genotype

AIMS

We assessed whether montelukast or formoterol provides additive effects to asthmatics not controlled on inhaled corticosteroids, by studying patients who were considered to be genetically susceptible to beta2-receptor down regulation and subsensitivity, and who expressed the homozygous glycine-16 beta2-receptor genotype.

METHODS

Fifteen corticosteroid-treated, mild to moderate persistent asthmatics received montelukast 10 mg once daily or formoterol 9 micro g twice daily for 2 weeks, separated by a 2-week placebo run-in and washout, in a double-blind, double-dummy, randomized crossover design. Bronchoprotection against adenosine monophosphate (AMP) challenge (primary endpoint), spirometry and blood eosinophils were measured at trough after placebo, first and last doses.

RESULTS

For AMP PC20vs placebo, there were sustained significant (P < 0.05) doubling dilution improvements following first (1.1; 95% CI 0.4, 1.9) and last (1.0; 95% CI 0.3, 1.8) doses of montelukast, and following first (1.3; 95% CI 0.1, 2.6) but not last (0.3; 95% CI -0.9, 1.6) doses of formoterol. Blood eosinophils (x 10(6) l(-1)) were significantly (P < 0.05) suppressed after the last dose of montelukast (-71; 95% CI -3, -140) compared with placebo, while formoterol exhibited a nonsignificant rise (20; 95% CI -92, 132). Neither treatment significantly improved FEV1, FEF25-75 or PEF after 2 weeks.

CONCLUSIONS

In genetically susceptible patients with the homozygous glycine-16 genotype, montelukast, but not formoterol, conferred sustained anti-inflammatory properties in addition to inhaled corticosteroid, which were dissociated from changes in lung function after 2 weeks. Thus, assessing lung function may miss potentially beneficial anti-inflammatory effects of montelukast when used as add-on therapy.

Actions other than smooth muscle relaxation may play a role in the protective effects of formoterol on the allergen-induced late asthmatic reaction

Long-acting beta(2)-adrenoceptor agonists attenuate the allergen-induced late asthmatic reaction. We evaluated whether other mechanisms in addition to airway smooth muscle relaxation may be implicated in this protective effect. The effects of formoterol (Foradil Aerolizer(TM), 24 microg dry powder) on the late asthmatic reaction were assessed by a randomised crossover factorial study in 24 patients with asthma. Four challenge/treatment combinations were tested: (A) saline/placebo, (B) saline/formoterol, (C) allergen/placebo, (D) allergen/formoterol. Formoterol and placebo were administered double blind after the last inhalation of the allergen or saline. FEV(1) was measured up to 32 h. The bronchodilator effect of formoterol was estimated as (B-A) and the overall protective effect as (D-C). The effect not due to bronchodilation was estimated as [(D-C)-(B-A)]/2. The bronchodilator effect of formoterol was statistically significant up to 5h (all P< or =0.015). Formoterol significantly attenuated the late asthmatic reaction between 3 and 32 h after allergen inhalation (all P< or =0.0012). The difference between this protective effect and the bronchodilator effect was statistically significant at 5 h and between 7 and 28 h after allergen inhalation (all P< or =0.035). Our results suggest that functional antagonism may not be the sole mechanism by which formoterol attenuates the allergen-induced late asthmatic reaction.

A randomized, double-blind trial of the effect of treatment with formoterol on clinical and inflammatory parameters of asthma in children

BACKGROUND

In addition to their bronchodilating effect, long-acting inhaled beta-agonists have recently been shown to have some anti-inflammatory properties.

OBJECTIVE

The purpose of this study was to evaluate the effect of formoterol on inflammatory mediators in children.

METHODS

In this double-blind, randomized, placebo-controlled trial, 34 children, aged 6 to 18 years, with moderate atopic asthma, were randomly allocated to receive formoterol or matching placebo for 4 weeks. The primary endpoint of this study was to determine changes in serum levels of inflammatory markers after treatment with formoterol; secondary endpoints included clinical efficacy and bronchial hyperreactivity. The following parameters were measured: symptom score, forced expiratory volume in 1 second (FEV1), provocative concentration of histamine causing a 20% fall in FEV1 (PC20) for histamine and peripheral blood eosinophil count, serum levels of eosinophil cationic protein (ECP), soluble receptor of interleukin-2 (sIL-2R), level of interleukin-4 (IL-4), level of soluble intercellular adhesion molecule-1 (ICAM-1), and immunoglobulin E (IgE) level before and after treatment.

RESULTS

Compared with placebo, treatment with formoterol significantly improved lung function. The mean value of FEV1 changed from 74% of predicted value before treatment to 80% of predicted value after treatment (P < 0.001). The mean concentration of eosinophil blood count before and after treatment was 379 and 310 cells/mm3 (P = 0.035); ECP was 93 and 83 mcg/L; and serum IL-4 was 0.13 and 0.11 pg/mL (P = 0.001). There was no significant difference between formoterol and placebo recipients in PC20H, and serum concentration of sIL-2R, sICAM-1, or IgE after treatment. The group that received formoterol showed improvement in pulmonary function as measured by FEV1 (P < 0.001), and PC20H (P = 0.04) after 4 weeks of treatment. These patients also showed improvement of clinical symptoms (P < 0.001). Serum marker measurements in the formoterol group showed decreased concentrations of eosinophil blood count, ECP, and IL-4, but there was no difference in before and after measurements of sIL-2R, sICAM-1, and IgE.

CONCLUSIONS

These results indicate that formoterol has measurable anti-inflammatory properties and can diminish asthma symptoms and bronchial hyperreactivity.

Low dose inhaled budesonide and formoterol in mild persistent asthma: the OPTIMA randomized trial

The optimal treatment for mild asthma is uncertain. We assessed the effects of adding a long-acting inhaled beta-agonist, formoterol, to low doses of an inhaled corticosteroid, budesonide, for 1 yr in subjects with mild asthma, receiving no or only a small dose of inhaled corticosteroid. The 698 corticosteroid free patients (Group A) were assigned to twice daily treatment with 100 microg budesonide, 100 microg budesonide plus 4.5 microg formoterol, or placebo. The 1,272 corticosteroid-treated patients (Group B) were assigned to twice daily treatment with 100 microg budesonide, 100 microg budesonide plus 4.5 microg formoterol, 200 microg budesonide, or 200 microg budesonide plus 4.5 microg formoterol. The main outcome variables were time to the first severe asthma exacerbation and poorly controlled asthma days. In Group A, budesonide alone reduced the risk for severe exacerbations by 60% and poorly controlled days by 48%; adding formoterol increased lung function with no change in other end points. By contrast, in Group B, adding formoterol reduced the risk for the first severe exacerbation and for poorly controlled days by 43 and 30%, respectively. Thus, in corticosteroid-free patients, low dose inhaled budesonide alone reduced severe exacerbations and improved asthma control, and in patients already receiving inhaled corticosteroid, adding formoterol was more effective than doubling the corticosteroid dose.

Formoterol used as needed--clinical effectiveness

A number of studies have already demonstrated the clinical effectiveness of formoterol when used as maintenance therapy in patients requiring both a beta2-agonist with a long duration of action and a regular inhaled corticosteroid. However, formoterol has a unique mechanism of action that gives it both fast- and long-acting properties. Hence the question arises as to whether formoterol can also be used as first-line reliever medication in addition to maintenance therapy. Compared with terbutaline, formoterol used as needed in steroid-treated mild to moderate asthma has superior efficacy, not only significantly improving peak flow, but also the exacerbation rate. In moderate to severe asthma, formoterol used as needed has demonstrated efficacy comparable with salbutamol and terbutaline in improving symptoms and lung function. Single doses of formoterol have also been shown to result in protection against exercise-induced bronchoconstriction for periods up to 12 h. Furthermore, bronchoprotection was maintained following repeated dosing, although further research is needed to confirm the duration of protection achieved with frequent and regular use. Initial research also suggests that formoterol is as effective and well tolerated as terbutaline in the treatment of acute asthma attacks. The evidence presented supports the use of formoterol on an as-needed basis for effective asthma control.

Unaltered perception of dyspnoea during treatment with long-acting beta2-agonists

There is the possibility that during treatment with inhaled long-acting beta2-agonists that a loss of perception of dyspnoea might occur and that the forced expiratory volume in one second (FEV1) might fall precipitously during bronchial provocation. This study investigated these possibilities during methacholine provocation, continued until there was > or =30% fall in FEV1, mimicking a moderate asthma attack. Nineteen asthmatic patients were asked to score their dyspnoea as a Borg score during provocation with methacholine. One hour prior to this provocation, the patients used the last morning dose of 14 days treatment with either formoterol (twice daily 24 microg by Turbuhaler), salmeterol (twice daily 100 microg by Diskhaler) and placebo in a double-blind, randomized, double-dummy, cross-over design. The perception of dyspnoea, expressed as the Borg score divided by the change in FEV1 at > or =30% fall in FEV1, was similar on the three test days at 0.067, 0.076 and 0.074%(-1) after formoterol, salmeterol and placebo treatment, respectively (p=0.16). The slope of the methacholine dose response curve did not differ (p=0.52). In conclusion, no suggestion was found for an abnormal perception of dyspnoea or an exaggerated fall in forced expiratory volume in one second during provocation with methacholine under long-acting beta2-agonist treatment.

Clinical outcome of adding long-acting beta-agonists to inhaled corticosteroids

Current asthma management guidelines state that where a patient is receiving a low to moderate dose of inhaled corticosteroids and is still experiencing symptoms the dose of corticosteroid should be increased and, if necessary, a long-acting bronchodilator should be added. Many studies have now shown that the addition of a beta2-agonist with long-acting properties is more effective at controlling asthma symptoms than increasing the dose of corticosteroid alone. The Formoterol and Corticosteroid Establishing Therapy (FACET) study was a 12-month study comparing exacerbation rates in patients treated with budesonide (100 microg or 400 microg) twice daily alone vs, treatment with budesonide (100 microg or 400 microg) twice daily plus formoterol 9 microg twice daily (delivered dose). The addition of formoterol reduced the rates of mild and severe exacerbations compared with budesonide alone, with the lowest rates seen in patients receiving high-dose budesonide and formoterol. There was no difference in the profile of exacerbations in any groups, indicating formoterol does not mask any signs of inflammation. The addition of formoterol to budesonide was also shown to result in improved lung function (as measured by peak expiratory flow rate and forced expiratory volume in 1 second), night-time awakenings and the use of as-needed medication when compared with an increase in the dose of budesonide. In all cases, increasing the dose of budesonide and addition of formoterol resulted in the most improvement and a significant increase in quality of life, measured by Asthma Quality of Life Questionnaire (AQLQ), was noted. In conclusion, the addition of formoterol to established treatment with inhaled corticosteroids provides superior asthma control compared with an increase in the dose of corticosteroid alone.

A placebo-controlled clinical trial of regular monotherapy with short-acting and long-acting beta(2)-agonists in allergic asthmatic patients

BACKGROUND

Some recent studies suggest that regular beta(2)-agonist use may result in inadequate control of asthma. It has been hypothesized that this occurs particularly in allergic asthmatic patients exposed to relevant allergens. Moreover, it is still unclear whether this occurs during the use of both short-acting and long-acting beta(2)-agonists.

METHODS

Asthmatic patients (n = 145) allergic to house dust mite (HDM) were randomly allocated to monotherapy with a short-acting beta(2)-agonist (SA; n = 48), a long-acting beta(2)-agonist (LA; n = 50), or placebo (n = 47), double blind, double dummy. The study covered three periods: (1) a 4-week run-in period, in which no changes took place; followed by (2) cessation of treatment with asthma medication including inhaled corticosteroids, introduction of allergen avoidance measures (active/placebo treatment) to lower HDM exposure in the active group, and an 8-week washout period to adjust patients to these changes; followed by (3) a 12-week study medication period. At the start of the 12-week medication period, and every 4 weeks thereafter, spirometric measurements (FEV(1) and provocative concentration of histamine causing a 20% fall in FEV(1) [PC(20)]) were performed. Peak flow and asthma symptoms were recorded daily. Additionally, at the start and every 6 weeks thereafter, dust samples were collected from mattresses and living room and bedroom floors to assess HDM (der p 1) concentrations. Effects on FEV(1), PC(20), peak flow, and asthma symptoms were analyzed with repeated-measurement analysis and corrected for the exposure to HDM allergens.

RESULTS

There were no significant differences among the three medication groups after 12 weeks for FEV(1). However, a significant decrease in mean FEV(1) percent predicted (95% confidence interval [CI]) was observed within the SA group: - 6.6 (- 10.4 to - 2.8) (p = 0.0002). A decrease in geometric mean PC(20) (95% CI) of - 1.2 (- 1.96 to - 0.44) doubling concentration was observed within the SA group (p = 0.05). No significant changes in FEV(1) and PC(20) were observed > 12 weeks within the LA group or the placebo group. There were neither changes in peak flow and asthma symptom scores among the three medication groups nor within the groups. Moreover, none of the parameters showed interactive effects with allergen exposure.

CONCLUSION

There were no significant differences among the three medication groups for FEV(1) and PC(20). The within-treatment group comparison showed a significant small decline in FEV(1) for the SA group (but not for the LA group), which could indicate that monotherapy with SAs might have negative effects on FEV(1). This was not seen during regular use of LAS: No clear pathophysiologic mechanism can explain these findings at the moment. Relatively high or low exposure to allergens did not alter these findings.

Adenosine and its role in asthma

Endogenous adenosine formed from ADP and AMP by the action of ATPase and 5'-nucleotidase is known to cause bronchoconstriction and asthma in humans. It has been suggested that this action of adenosine is due to its binding to specific purino receptors in the mast cells in the lungs and consequent release of mediators which elicit bronchoconstriction and asthma. The release of these mediators leading to asthma was also believed to be due to vagal stimulation by adenosine. Though the role of adenosine in causing bronchoconstriction leading to asthma is well confirmed the actual mode of action and details of the mechanisms involved in the clinical manifestation of asthma remain unclear.

Protection against cold air and exercise-induced bronchoconstriction while on regular treatment with Oxis

This study aimed to compare the duration of protection against exercise-induced bronchoconstriction (EIB) after inhalation of formoterol (Oxis) Turbuhaler with that of terbutaline Turbuhaler and placebo Turbuhaler in asthmatic patients treated regularly with formoterol Turbuhaler 9 microg b.i.d. and inhaled steroids. The study. performed at three centres (Göteborg and Lund, Sweden, and Trondheim, Norway), consisted of an open-label part with formoterol Turbuhaler 9 microg b.i.d. and a randomized, double-blind, cross-over part with a single dose (on top of the regular treatment) of either formoterol Turbuhaler 9 microg, terbutaline Turbuhaler 0.5 mg or placebo Turbuhaler. The patients attended the clinic six times: twice for screening visits, three times for randomized treatment and once for a follow-up visit. Patients received regular b.i.d. treatment with formoterol 9 microg for a mean period of 16 days. Formoterol gave a post-exercise fall of 12, 10, 15 and 17% in forced expiratory volume in 1 sec (FEV1) 15 min, 4, 8 and 12 h after inhalation. The differences compared with placebo (falls of 26, 22, 23 and 22%) and terbutaline (falls of 17, 18, 22 and 22%) were all statistically significant (P<0.05 for all comparisons). Patients on regular treatment with formoterol Turbuhaler 9 microg b.i.d. have a significant protection against EIB up to 12 h after inhalation of formoterol 9 microg. The protection was also significantly better than that of terbutaline Turbuhaler 0.5 mg.

Evaluation of salmeterol or montelukast as second-line therapy for asthma not controlled with inhaled corticosteroids

OBJECTIVE

To assess the addition of a leukotriene receptor antagonist and a long-acting beta(2)-agonist as second-line therapy in asthma.

DESIGN

Placebo-controlled, double-dummy, crossover study.

SETTING

Outpatient clinic.

PATIENTS

Twenty patients with persistent asthma not controlled with inhaled corticosteroid therapy.

INTERVENTIONS

Montelukast 10 mg once daily, or salmeterol, 50 microg bid, each for 2 weeks with 1-week run-in and washout placebo periods.

MEASUREMENTS AND RESULTS

Adenosine monophosphate (AMP) bronchial challenge, blood eosinophil count (EOS), exhaled nitric oxide, and lung function after both placebo periods and after the first and last doses of each active treatment. Patients recorded their domiciliary peak expiratory flow (PEF), asthma symptoms, and rescue bronchodilator requirement (RES) twice daily throughout the study. For the primary end point of the provocative concentration of AMP causing a 20% fall in FEV(1), compared to placebo (47.5 +/- 13.0 mg/mL), there were significant differences with the first (114.1 +/- 36.9 mg/mL) and last (94.2 +/- 30.4 mg/mL) doses of montelukast as well as the first (160.1 +/- 64.5 mg/mL) but not the last (70.1 +/- 23.7 mg/mL) dose of salmeterol. Only montelukast produced significant suppression of the EOS. Neither drug affected exhaled nitric oxide levels. There were significant improvements with the first doses of salmeterol for all parameters of lung function. After 2 weeks of treatment, there were significant improvements with both drugs for RES and morning PEF. There were no significant differences between drugs for any end points except EOS.

CONCLUSIONS

Montelukast and salmeterol exhibited significant improvements in asthma control when given as second-line therapy. Montelukast also produced significant effects on AMP challenge and EOS suggesting anti-inflammatory activity.

Effects of once-daily formoterol and budesonide given alone or in combination on surrogate inflammatory markers in asthmatic adults

OBJECTIVES

We wished to evaluate the effects of once-daily combination therapy on surrogate inflammatory markers.

METHODS

Fifteen patients with atopic persistent asthma were evaluated (mean age, 32.4 years; FEV(1), 75.2% predicted) in a randomized, double-blind, double-dummy, placebo-controlled crossover study with a 1-week placebo washout period, comparing the following once-daily nighttime treatments: (1) formoterol (FM), 12 microg, for 2 weeks and FM, 24 microg, for 2 weeks; or (2) budesonide (BUD), 400 microg, for 2 weeks and BUD, 800 microg, for 2 weeks; or (3) FM, 12 microg, plus BUD, 400 microg, for 2 weeks and FM, 24 microg, plus BUD, 800 microg, for 2 weeks. Adenosine monophosphate (AMP) bronchial challenge, exhaled nitric oxide (NO), and serum eosinophilic cationic protein (ECP) were evaluated at 12 h postdosing after administration of each placebo and after 2 and 4 weeks of each treatment.

RESULTS

The results of AMP challenge (provocative concentration causing a 20% fall in FEV(1)) at 4 weeks showed significant (p<0.05) improvements after patients had received all active treatments compared to placebo (20 mg/mL), with FM plus BUD, 261 mg/mL, being superior (p<0.05) to FM alone, 82 mg/mL, but not to BUD, 201 mg/mL. NO and ECP showed significant (p<0.05) reductions compared to placebo with FM plus BUD or BUD alone but not with FM alone. Combination therapy was associated with optimal patient preference (rank order, FM plus BUD > FM > BUD; p<0.0005), highest domiciliary peak expiratory flow, and lowest rescue inhaler usage. All three treatments produced equivalent improvements in spirometry.

CONCLUSIONS

Patients preferred once-daily combination therapy, but this had no greater effect on inflammatory markers than therapy with BUD alone. FM alone had no anti-inflammatory activity but exhibited bronchoprotection. This emphasizes the importance of first optimizing anti-inflammatory control with inhaled corticosteroids before considering adding a regular long-acting beta(2)-agonist.

The effect of long-acting beta2-agonists on airway inflammation in asthmatic patients

Early observations suggested that the inhibition by long-acting beta2-agonists (LABAs) of non-specific bronchial hyperresponsiveness following allergen challenge was unrelated to bronchodilation or functional antagonism and might be a reflection of anti-inflammatory activity. Investigation of the effect of LABAs on airway inflammatory responses has demonstrated an inhibition of eosinophil recruitment in allergen challenge studies. Nevertheless, results from biopsy and other studies suggest that the chronic inflammatory process in asthma patients is unaffected by these drugs. There is no evidence from biopsy studies that LABAs are pro-inflammatory or that they mask existing inflammation. The beneficial effects of LABAs in allergen challenge are probably mediated through stabilization of mast cells. Recent evidence suggests that LABAs may reduce numbers of neutrophils and their associated markers; this observation needs to be confirmed in future studies and its relevance to the treatment of asthma determined.

Additive bronchoprotective and bronchodilator effects with single doses of salmeterol and montelukast in asthmatic patients receiving inhaled corticosteroids

OBJECTIVE

We wished to evaluate whether the combination of a leukotriene receptor antagonist and long-acting beta(2)-agonist might confer additive beneficial effects in terms of bronchoprotection and bronchodilatation, in mild to moderate asthmatic patients who were suboptimally controlled on inhaled corticosteroids alone.

METHODS

Twelve asthmatic patients were enrolled into a single-blind, placebo-controlled, crossover study, receiving additive therapy as either of the following: (1) montelukast alone, 10 mg (ML(10)); (2) inhaled salmeterol alone, 50 microg (SM(50)); (3) ML(10) and SM(50); (4) ML(10) and inhaled salmeterol, 100 microg (SM(100)); or (5) placebo inhaler and tablet. Trough measurements were made of adenosine monophosphate (AMP) bronchial challenge (the provocative concentration of a drug [AMP] causing a fall of >/= 20% in FEV(1) [PC(20)]) as the primary end point, and spirometry, following single doses of either placebo or active treatments (12 h after salmeterol, and 24 h after monteleukast, respectively).

RESULTS

Compared to placebo, all active treatments led to significant improvements (p < 0.05) in geometric mean AMP-PC(20): placebo, 42 mg/mL; ML(10), 106 mg/mL; SM(50), 115 mg/mL; ML(10) and SM(50), 183 mg/mL; and ML(10) and SM(100), 247 mg/mL. The effects of montelukast and salmeterol were numerically additive, with ML(10) and SM(100) being significantly different (p < 0.05) from ML(10) alone. For mean FEV(1) and forced expiratory flow rate between 25% and 75% of vital capacity, there were significant differences (p < 0.05) between both combination therapies vs ML(10) alone.

CONCLUSIONS

Our results suggest additive benefits of a single dose of a long-acting beta(2)-agonist and leukotriene antagonist, in terms of bronchoprotection and bronchodilation. Further studies in more severe asthmatics are required to evaluate long-term clinical effects.