Benefit-risk assessment of long-acting beta2-agonists in asthma

B2 adrenergic receptor gene polymorphism effect on childhood asthma severity and response to treatment

BackgroundAlterations of B2 adrenergic receptor (β₂AR) can modulate the severity of asthma and the response to treatment. Therefore, we aimed to evaluate β₂AR gene polymorphism at codons 16 and 27 and their effect on asthma severity and response to treatment in asthmatic children.MethodsCase-control study was conducted on 156 children; 104 of them had bronchial asthma and 52 were healthy children (control group). Subjects of the study underwent history taking, clinical examination, pulmonary function tests, serum IgE level assessment, and identification of β₂AR-16 A46G and β₂AR-27 C79G polymorphism using PCR-Restriction Fragment length polymorphisms (RFLP) test.ResultsThere was a higher frequency of Arg-Gly genotypes (odds ratio (OR)=6.57; confidence interval (CI): 2.42-18.81, P<0.001) and lower frequency of Arg-Arg (OR=4.7; CI: 2.05-10.95, P<0.001) among asthmatic children compared with that among controls at codon 16. The presence or absence of Gly16 or Glu27 either homozygous or heterozygous for both correlated with the grade of asthma severity. The presence of heterozygous Arg-Gly and Gln-Glu gives a better response to drug therapy than the presence of Gly-Gly and Glu-Glu genotypes at codons 16 and 27.ConclusionPolymorphism of β₂AR at codons 16 and 27 correlates with asthma severity and response to treatment in asthmatic children.

Efficacy and safety of fluticasone propionate/formoterol fumarate in pediatric asthma patients: a randomized controlled trial

BACKGROUND

The efficacy and safety of fluticasone propionate/formoterol fumarate pressurized metered-dose inhaler (pMDI) (fluticasone/formoterol; Flutiform®; 100/10 µg b.i.d.) was compared with fluticasone propionate (Flixotide® Evohaler® pMDI; 100 µg b.i.d.) and fluticasone/salmeterol (Seretide® Evohaler® pMDI; 100/50 µg b.i.d.) in a pediatric asthma population (EudraCT number: 2010-024635-16).

METHODS

A double-blind, double-dummy, parallel group, multicenter study. Patients, aged 5-<12 years with persistent asthma ⩾ 6 months and forced expiratory volume in 1 s (FEV1) ⩽ 90% predicted were randomized 1:1:1 to 12 weeks' treatment. The study objectives were to demonstrate superiority of fluticasone/formoterol to fluticasone and non-inferiority to fluticasone/salmeterol.

RESULTS

A total of 512 patients were randomized: fluticasone/formoterol, 169; fluticasone, 173; fluticasone/salmeterol, 170. Fluticasone/formoterol was superior to fluticasone for the primary endpoint: change from predose FEV1 at baseline to 2 h postdose FEV1 over 12 weeks [least squares (LS) mean difference 0.07 l; 95% confidence interval (CI) 0.03, 0.11; p < 0.001] and the first key secondary endpoint, FEV1 area under the curve over 4 hours (AUC0-4 h) at week 12 (LS mean difference 0.09 l; 95% CI: 0.04, 0.13; p < 0.001). Per a prespecified non-inferiority margin of -0.1 l, fluticasone/formoterol was non-inferior to fluticasone/salmeterol for the primary endpoint (LS mean difference 0.00 l; 95% CI -0.04, 0.04; p < 0.001) and first key secondary endpoint (LS mean difference 0.01; 95% CI -0.03, 0.06; p < 0.001). Fluticasone/formoterol was non-inferior to fluticasone/salmeterol for the second key secondary endpoint, change from predose FEV1 over 12 weeks (treatment difference -0.02 l; 95% CI -0.06, 0.02; p < 0.001), but was not superior to fluticasone for this endpoint (LS mean difference 0.03 l; 95% CI -0.01, 0.07; p = 0.091). All treatments elicited large improvements from baseline to week 12 for the Pediatric Asthma Quality of Life Questionnaire (LS mean change 0.76 to 0.85 units) and Asthma Control Questionnaire (LS mean change -1.03 to -1.13 units). Few severe exacerbations were seen (fluticasone/formoterol: two; fluticasone/salmeterol: two). All treatments were well tolerated.

CONCLUSIONS

This study supports the efficacy and safety of fluticasone/formoterol in a pediatric asthma population and its superiority to fluticasone.

Association between Selective Beta-adrenergic Drugs and Blood Pressure Elevation: Data Mining of the Japanese Adverse Drug Event Report (JADER) Database

Selective beta-adrenergic drugs are used clinically to treat various diseases. Because of imperfect receptor selectivity, beta-adrenergic drugs cause some adverse drug events by stimulating other adrenergic receptors. To examine the association between selective beta-adrenergic drugs and blood pressure elevation, we reviewed the Japanese Adverse Drug Event Reports (JADERs) submitted to the Japan Pharmaceuticals and Medical Devices Agency. We used the Medical Dictionary for Regulatory Activities (MedDRA) Preferred Terms extracted from Standardized MedDRA queries for hypertension to identify events related to blood pressure elevation. Spontaneous adverse event reports from April 2004 through May 2015 in JADERs, a data mining algorithm, and the reporting odds ratio (ROR) were used for quantitative signal detection, and assessed by the case/non-case method. Safety signals are considered significant if the ROR estimates and lower bound of the 95% confidence interval (CI) exceed 1. A total of 2021 reports were included in this study. Among the nine drugs examined, significant signals were found, based on the 95%CI for salbutamol (ROR: 9.94, 95%CI: 3.09-31.93) and mirabegron (ROR: 7.52, 95%CI: 4.89-11.55). The results of this study indicate that some selective beta-adrenergic drugs are associated with blood pressure elevation. Considering the frequency of their indications, attention should be paid to their use in elderly patients to avoid adverse events.

Pharmacogenomics of long-acting β2-agonists

INTRODUCTION

Long-acting β2-agonists are an effective class of drugs, when combined with inhaled corticosteroids, for reducing symptoms and exacerbations in patients with asthma that is not adequately controlled by inhaled corticosteroids alone. However, because this class of drugs has been associated with severe adverse events, including hospitalization and death in small numbers of patients, efforts to identify a pharmacogenetic profile for patients at risk has been diligently investigated.

AREAS COVERED

The PubMed search engine of the National Library of Medicine was used to identify English-language and non-English language articles published from 1947 to March 2015 pertinent to asthma, pharmacogenomics, and long-acting β2-agonists. Keywords and topics included: asthma, asthma control, long-acting β2-agonists, salmeterol, formoterol, pharmacogenetics, and pharmacogenomics. This strategy was also used for the Cochrane Library Database and CINAHL. Reference types were randomized controlled trials, reviews, and editorials. Additional publications were culled from reference lists. The publications were reviewed by the authors and those most relevant were used to support the topics covered in this review.

EXPERT OPINION

Children, who carry the ADRB2 Arg16Arg genotype, may be at greater risk than adults for severe adverse events. Rare ADRB2 variants appear to provide better clues for identifying the at-risk population of asthmatics.

Chronic treatment in vivo with β-adrenoceptor agonists induces dysfunction of airway β(2) -adrenoceptors and exacerbates lung inflammation in mice

BACKGROUND AND PURPOSE

Inhalation of a β-adrenoceptor agonist (β-agonist) is first-line asthma therapy, used for both prophylaxis against, and acute relief of, bronchoconstriction. However, repeated clinical use of β-agonists leads to impaired bronchoprotection and, in some cases, adverse patient outcomes. Mechanisms underlying this β(2) -adrenoceptor dysfunction are not well understood, due largely to the lack of a comprehensive animal model and the uncertainty as to whether or not bronchorelaxation in mice is mediated by β(2) -adrenoceptors. Thus, we aimed to develop a mouse model that demonstrated functional β-agonist-induced β(2) -adrenoceptor desensitization in the context of allergic inflammatory airway disease.

EXPERIMENTAL APPROACH

We combined chronic allergen exposure with repeated β-agonist inhalation in allergen-treated BALB/C mice and examined the contribution of β(2) -adrenoceptors to albuterol-induced bronchoprotection using FVB/NJ mice with genetic deletion of β(2) -adrenoceptors (KO). Associated inflammatory changes - cytokines (ELISA), cells in bronchoalevolar lavage and airway remodelling (histology) and β(2) -adrenoceptor density (radioligand binding) - were also measured. KEY RESULTS β(2) -Adrenoceptors mediated albuterol-induced bronchoprotection in mice. Chronic treatment with albuterol induced loss of bronchoprotection, associated with exacerbation of the inflammatory components of the asthma phenotype.

CONCLUSIONS AND IMPLICATIONS

This animal model reproduced salient features of human asthma and linked loss of bronchoprotection with airway pathobiology. Accordingly, the model offers an advanced tool for understanding the mechanisms of the effects of chronic β- agonist treatment on β-adrenoceptor function in asthma. Such information may guide the clinical use of β-agonists and provide insight into development of novel β-adrenoceptor ligands for the treatment of asthma.

Prescription patterns in asthma patients initiating salmeterol in UK general practice: a retrospective cohort study using the General Practice Research Database (GPRD)

BACKGROUND

An association between salmeterol, a long-acting β(2)-agonist (LABA), use and rare serious asthma events or asthma mortality was observed in two large clinical trials. This has resulted in heightened scrutiny of LABAs and comprehensive reviews by regulatory agencies.

OBJECTIVE

The aim of this retrospective observational cohort study was to better characterize salmeterol medication use patterns in the UK. We describe asthma prescription patterns in a cohort of patients (n =17,745) in the General Practice Research Database who initiated treatment with salmeterol-containing prescriptions between 2003 and 2006, including salmeterol and salmeterol/fluticasone propionate in a single device.

METHODS

Prescriptions patterns by medication class, including concurrent prescription of salmeterol with inhaled corticosteroids (ICS), were described using 6-month intervals in the 1-year period before and after the salmeterol-containing index prescription.

RESULTS

In the 0- to 6-month and 7- to 12-month periods prior to initiation of the salmeterol-containing prescription, the cohort experienced worsening of asthma, measured by an increase in the proportion of patients with prescriptions for short-acting β-agonists [SABA] (73-89%), ICS (70-81%) and systemic corticosteroids (14-28%). Nearly all patients prescribed salmeterol were concurrently prescribed ICS (≥95% within 90 days). In the 12 months following initiation of the salmeterol-containing prescription, a decrease in asthma prescriptions was observed.

DISCUSSION

These results support the appropriate prescribing of salmeterol-containing medications, as per recommendations in asthma treatment guidelines in the UK.

CONCLUSION

Salmeterol was consistently prescribed as an add-on asthma-controller with an ICS for most patients, and was associated with improvements in asthma control, as indicated by decreases in SABA and systemic corticosteroid prescriptions following salmeterol introduction.

Pharmacogenetics and functional genomics in asthma

Asthma is a complex phenotype caused by a combination of genetic and environmental factors that remain poorly understood. The common variants involved in the pathogenesis of asthma have proved difficult to identify by candidate gene association studies. As a result, few genetic variants influencing clinical response to asthma and allergy medications have been uncovered. Recently, genome-wide association, which is more robust in identifying common predisposition variants, has been applied to disorders such as asthma. As genome-wide associations are hypothesis-free, they raise the possibility of identifying novel biological pathways that could be translated to the future benefit of patients through improved diagnostic and therapeutic measures in the form of personalized medicine. This review addresses both recent advances in the genetics of asthma and their potential in transforming the treatment of the disorder into more individualized care in the near future.

Safety of long-acting beta2-agonists in the treatment of asthma

Several studies suggested an association between the regular use of beta2-agonists and asthma deaths. Whether this association represents adverse effects of beta -agonist use or is entirely due to disease severity is a matter of ongoing debate. Previous literature indicates that confounding by poor asthma control may explain the apparent deleterious effects of inhaled beta2-agonists. Tolerance to nonbronchodilator effects of beta2-agonists may account for the increase in reactivity to indirect bronchoconstrictor challenges and explain why some studies have demonstrated enhanced bronchoconstriction in patients with asthma after regular beta 2-agonist therapy. Nonetheless, the salmeterol multi-centre asthma research trial (SMART) found more asthma deaths (13 vs 3) and life-threatening asthma events (37 vs 22) in the salmeterol-treated asthmatic patients, although it was documented that among African-Americans, 5 times as many deaths and near-deaths from asthma occurred in those given salmeterol than in those given placebo, and among patients with asthma not using an inhaled corticosteroid (ICS) as a preventive (controller) medication, again more deaths and near-deaths from asthma occurred in those given salmeterol than in those given placebo. Only 38% of the African-Americans who participated in the study used an ICS. As a result of the findings from the SMART, FDA issued a public health advisory to highlight that long-acting beta2-agonists (LABAs) should not be the first medicine used to treat asthma. LABAs should be added to the asthma treatment plan only if other medicines, including the use of low-or-medium dose ICSs, do not control asthma. However, despite all of the concerns raised by the SMART, inhaled beta2-agonists remain the most effective bronchodilators available for the immediate relief of asthma symptoms and, as such, remain an important component of asthma management. Obviously, there are concerns about LABA treatment as monotherapy for asthma. Patients with asthma should be initiated and maintained on sufficiently high doses of ICSs and only patients whose asthma cannot be controlled should receive additional LABAs on a regular basis.

Beta-arrestins specifically constrain beta2-adrenergic receptor signaling and function in airway smooth muscle

Chronic use of inhaled beta-agonists by asthmatics is associated with a loss of bronchoprotective effect and deterioration of asthma control. Beta-agonist-promoted desensitization of airway smooth muscle beta-2-adrenergic receptors, mediated by G protein-coupled receptor kinases and arrestins, is presumed to underlie these effects, but such a mechanism has never been demonstrated. Using in vitro, ex vivo, and in vivo murine models, we demonstrate that beta-arrestin-2 gene ablation augments beta-agonist-mediated airway smooth muscle relaxation, while augmenting beta-agonist-stimulated cyclic adenosine monophosphate production. In cultures of human airway smooth muscle, small interfering RNA-mediated knockdown of arrestins also augments beta-agonist-stimulated cyclic adenosine monophosphate production. Interestingly, signaling and function mediated by m2/m3 muscarinic acetylcholine receptors or prostaglandin E(2) receptors were not affected by either beta-arrestin-2 knockout or arrestin knockdown. Thus, arrestins are selective regulators of beta-2-adrenergic receptor signaling and function in airway smooth muscle. These results and our previous findings, which demonstrate a role for arrestins in the development of allergic inflammation in the lung, identify arrestins as potentially important therapeutic targets for obstructive airway diseases.

Interactive effects of steroids and beta-agonists on accumulation of type 2 T cells

BACKGROUND

Airway inflammation associated with asthma has been reported to be either unaffected or slightly increased by inhaled beta-agonist monotherapy, and concerns regarding disease exacerbations with continuous long-acting beta-agonist monotherapy have prompted the recommendation of concomitant steroid treatment.

OBJECTIVES

Using peripheral blood lymphocytes from asthmatic subjects, we aimed to determine (1) whether short- or long-acting beta-agonists increase IL-13-producing (IL-13+ or IFN-gamma-producing (IFN-gamma+ T-cell numbers and (2) the ability of the corticosteroid budesonide to reverse these effects.

METHODS

Peripheral blood lymphocytes from asthmatic subjects were cultured 6 days ex vivo with IL-2 and various concentrations of albuterol, formoterol, and budesonide. Numbers of IL-13+ and IFN-gamma+ T cells were determined by means of flow cytometric analysis.

RESULTS

Both albuterol and formoterol increased IL-2-stimulated accumulation of IL-13+ T cells, and this increase was highest at concentrations approximating the dissociation constant of each beta-agonist for the beta(2)-adrenergic receptor. Budesonide at greater than 1 nmol/L reversed the augmenting effects of beta-agonists on IL-13+ T-cell accumulation, and budesonide at greater than 10 nmol/L inhibited increases in IL-13+ T cells stimulated by IL-2. Budesonide decreased, whereas beta-agonist did not affect, numbers of total and IFN-gamma+ T cells in IL-2-stimulated cultures.

CONCLUSION

beta-Agonists at physiologically and clinically relevant concentrations stimulate increased antigen-independent, cytokine-stimulated accumulation, specifically of type 2 T cells from asthmatic subjects. The corticosteroid budesonide potently reverses this effect.

Recent development in pharmacogenomics: from candidate genes to genome-wide association studies

Genetic diversity, most notably through single nucleotide polymorphisms and copy-number variation, together with specific environmental exposures, contributes to both disease susceptibility and drug response variability. It has proved difficult to isolate disease genes that confer susceptibility to complex disorders, and as a consequence, even fewer genetic variants that influence clinical drug responsiveness have been uncovered. As such, the candidate gene approach has largely failed to deliver and, although the family-based linkage approach has certain theoretical advantages in dealing with common/complex disorders, progress has been slower than was hoped. More recently, genome-wide association studies have gained increasing popularity, as they enable scientists to robustly associate specific variants with the predisposition for complex disease, such as age-related macular degeneration, Type 2 diabetes, inflammatory bowel disease, obesity, autism and leukemia. This relatively new methodology has stirred new hope for the mapping of genes that regulate drug response related to these conditions. Collectively, these studies support the notion that modern high-throughput single nucleotide polymorphism genotyping technologies, when applied to large and comprehensively phenotyped patient cohorts, will readily reveal the most clinically relevant disease-modifying and drug response genes. This review addresses both recent advances in the genotyping field and highlights from genome-wide association studies, which have conclusively uncovered variants that underlie disease susceptibility and/or variability in drug response in common disorders.

The effect of fixed combination of fluticasone and salmeterol on asthma drug utilization, asthma drug cost, and episodes of asthma exacerbations

OBJECTIVE

This study evaluated the use and drug costs of inhaled corticosteroids (ICSs), long-acting beta2-agonists (LABAs), and fluticasone propionate and salmeterol in a fixed-dose combination (FSC) and their relationship to asthma exacerbations before and after the market introduction of FSC in April 2001.

METHODS

This is a retrospective analysis of employer-sponsored health insurance claims filed between January 1, 1998, and December 31, 2003 to detect impact of introduction of FSC (approved by the US Food and Drug Administration in August 2000) on utilization and cost of FSC, any ICS (excluding FSC), and any LABA (excluding FSC) along with utilization of medical services related to asthma exacerbations. Asthma medications were identified using National Drug Codes and Redbook, whereas asthma exacerbations were identified using ICD-9-CM primary diagnosis code 493.x. These medical and pharmacy claims were converted to rates per 100 asthma office visits.

RESULTS

For all ICSs, the average pharmacy claims per 100 office visits increased from 383 in the year before FSC was introduced to 407 (120 [29.5%] were for FSC and 287 [70.5%] were for single-entity ICSs) in 2003. LABA prescribing increased from 72 in the year before FSC to 147 (120 from FSC, 27 single-entity LABA) in 2003 (p < 0.001). An additional $13,511 per 100 asthma office visits was spent on the FSC product (p < 0.001). After the introduction of FSC, there was no significant difference in asthma admissions (p = 0.17), whereas emergency department (ED) visits increased by 0.92 visits per 100 office visits (p = 0.03). The diagnosis and severity of asthma was inferred from the pharmacy claims and patients with chronic obstructive pulmonary disease could not be excluded. In addition, the study was not designed to assess the impact of other asthma medications on the disease and/or associated costs, and patient adherence to claimed medication could not be monitored.

CONCLUSIONS

The introduction of FSC was associated with increased LABAs/FSC patient exposure and expenditure with no change in asthma hospitalizations and an increase in ED visits.

Tolerability profiles of leukotriene receptor antagonists and long-acting beta2-adrenoceptor agonists in combination with inhaled corticosteroids for treatment of asthma: a review

Inhaled corticosteroids, long-acting beta2-adrenoceptor agonists, and leukotriene receptor antagonists are widely used for treatment of asthma. Inhaled corticosteroids are recommended as first-line therapy, whereas long-acting beta2-adrenoceptor agonists and leukotriene receptor antagonists are indicated as add-on therapy in patients not adequately controlled with corticosteroids alone. A number of studies have investigated the efficacy of combinations of these drugs in asthma, but several issues concerning the safety of these treatments are highly debated. This review provides a critical appraisal of the tolerability profiles of long-acting beta2-agonists and leukotriene receptor antagonists used in combination with inhaled corticosteroids for the treatment of asthma.

The safety and effects of the beta-blocker, nadolol, in mild asthma: an open-label pilot study

Beta-blockers are currently contraindicated in asthma because their acute administration may be associated with worsening bronchospasm. However, their effects and safety with their chronic administration are not well evaluated. The rationale for this pilot study was based on the paradigm shift that was observed with the use of beta-blockers in congestive heart failure, which once contraindicated because of their acute detrimental effects, have now been shown to reduce mortality with their chronic use. We hypothesized that certain beta-blockers may also be safe and useful in chronic asthma therapy. In this prospective, open-label, pilot study, we evaluated the safety and effects of escalating doses of the beta-blocker, nadolol, administered over 9 weeks to 10 subjects with mild asthma. Dose escalation was performed on a weekly basis based on pre-determined safety, lung function, asthma control and hemodynamic parameters. The primary objective was to evaluate safety and secondary objectives were to evaluate effects on airway hyperresponsiveness, and indices of respiratory function. The escalating administration of nadolol was well tolerated. In 8 out of the 10 subjects, 9 weeks of nadolol treatment produced a significant, dose-dependent increase in PC20 that reached 2.1 doubling doses at 40 mg (P<0.0042). However, there was also a dose-independent 5% reduction in mean FEV1 over the study period (P<0.01). We conclude that in most patients with mild asthma, the dose-escalating administration of the beta-blocker, nadolol, is well tolerated and may have beneficial effects on airway hyperresponsiveness. Our findings warrant further testing in future larger trials.

The influence of the AA 16 beta 2-adrenoceptor polymorphism on systemic and airway responses in asthma

BACKGROUND

The impact of the polymorphic amino acids 16 and 27 of the beta 2-adrenoceptor (beta 2-AR) on the susceptibility to bronchodilator tolerance remains unclear since clinical studies thus far have shown discordant results. Tolerance towards the effects of inhaled beta 2-AR agonists generally is more easily shown for systemic parameters than for airway effects and can be substantial. This study evaluates whether differences exist between position 16 homozygous genotyped asthmatics, in tolerance development towards airway responses and the systemic effect hypokalemia.

METHODS

Twenty patients were genotyped for amino acids 16 and 27 of the beta 2-AR gene. Time-effect curves for FEV1 and serum potassium concentration were constructed after s.c. administration of terbutaline after two-week treatment periods with either terbutaline inhalation or matching placebo in a double-blind, randomised and cross-over design. Statistical analysis was done by a repeated measures multivariate analysis on area under time-effect curve (AUC).

MAIN RESULTS

Pre-treatment with inhaled terbutaline did not influence the improvement in FEV1 in response to s.c. terbutaline and there were no significant differences between Arg-16 and Gly-16 individuals in this respect. Pre-treatment with inhaled terbutaline resulted in an overall increase of baseline plasma potassium before administration of s.c. terbutaline (3.78-3.95 mmol/L, p=0.034). However, this effect appeared to be solely confined to the Arg-16 homozygous individuals, leading to a statistically highly significant difference between the Arg-16 and Gly-16 subjects (p=0.005). However, there was no genotype related difference in the decrease in plasma potassium response to s.c. terbutaline relative to baseline.

CONCLUSION

In patients carrying the Arg-16 genotype the development of hypokalemia by s.c. terbutaline is attenuated after pre-treatment with inhaled terbutaline, be it on the basis of higher baseline values.

Arginine-16 beta2 adrenoceptor genotype predisposes to exacerbations in young asthmatics taking regular salmeterol

BACKGROUND

The homozygous presence of the arginine-16 variant of the beta(2) adrenoceptor gene ADRB2 reverses the benefits from the regular use of short acting beta(2) agonists in asthmatic adults compared with the homozygous glycine-16 genotype. We studied the effect of this polymorphic variation on asthma exacerbations in children and young adults and its relation to long acting beta(2) agonists.

METHODS

A cross-sectional survey was undertaken using electronic records, direct interviews, and genotype determination of position 16 and 27 of the ADRB2 gene in DNA from mouthwash samples of 546 children and young asthmatics attending paediatric and young adult asthma clinics in Tayside, Scotland during 2004-5. The primary outcome measure was asthma exacerbations over the previous 6 months.

RESULTS

There was an increased hazard of asthma exacerbations across all treatment steps of the British Thoracic Society (BTS) asthma guidelines when the homozygous genotypes Arg/Arg and Gly/Gly were compared (OR 2.05, 95% CI 1.19 to 3.53, p = 0.010), particularly in patients treated with salmeterol (OR 3.40, 95% CI 1.19 to 9.40, p = 0.022). The Glu27Gln polymorphism had no significant effect on asthma exacerbations in any treatment group.

CONCLUSIONS

The arginine-16 genotype of ADRB2 predisposes to exacerbations in asthmatic children and young adults, particularly in those exposed to regular salmeterol. This may be explained by genotype selective salmeterol induced downregulation and impaired receptor coupling, and associated subsensitivity of the response.

Inhaled beta2-adrenoceptor agonists: cardiovascular safety in patients with obstructive lung disease

Although large surveys have documented the favourable safety profile of beta(2)-adrenoceptor agonists (beta(2)-agonists) and, above all, that of the long-acting agents, the presence in the literature of reports of adverse cardiovascular events in patients with obstructive airway disease must induce physicians to consider this eventuality. The coexistence of beta(1)- and beta(2)-adrenoceptors in the heart clearly indicates that beta(2)-agonists do have some effect on the heart, even when they are highly selective. It should also be taken into account that the beta(2)-agonists utilised in clinical practice have differing selectivities and potencies. beta(2)-agonist use has, in effect, been associated with an increased risk of myocardial infarction, congestive heart failure, cardiac arrest and sudden cardiac death. Moreover, patients who have either asthma or chronic obstructive pulmonary disease may be at increased risk of cardiovascular complications because these diseases amplify the impact of these agents on the heart and, unfortunately, are a confounding factor when the impact of beta(2)-agonists on the heart is evaluated. Whatever the case may be, this effect is of particular concern for those patients with underlying cardiac conditions. Therefore, beta(2)-agonists must always be used with caution in patients with cardiopathies because these agents may precipitate the concomitant cardiac disease.

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.

Limited beta2-adrenoceptor haplotypes display different agonist mediated airway responses in asthmatics

BACKGROUND

In vitro and some in vivo studies suggested that genetic haplotypes may have an impact on beta2-agonist mediated airway responses in asthmatics. Due to strong linkage disequilibrium the single nucleotide polymorphisms (SNPs) in the beta2-adrenoceptor gene result in only a limited number of haplotypes. We intended to evaluate the impact of beta2-adrenoceptor haplotypes on beta2-agonist mediated airway responses and the development of tolerance in mild to moderate asthmatics.

METHODS

Patients were genotyped for the part of the beta2-adrenoceptor gene with a known bearing on receptor function and regulation. Cumulative dose response curves of fenoterol versus PD20 methacholine and FEV1 were constructed after 2 week treatment periods with either terbutaline or placebo in a double blind, randomised and cross-over design. Analysis of the dose response curves was based on a repeated measurement analysis of covariance.

RESULTS

In our study population comprising 45 asthmatic patients, we found three limited allelic haplotypes, resulting in six different genotypes. Our data support the existence of differences between these six genotypes both in the shape of the dose response relationship of the beta2-adrenoceptor agonist fenoterol as well as in the propensity to develop tolerance for these effects by pre-treatment with terbutaline. However, this could only be substantiated for the endpoint PD20 methacholine.

CONCLUSION

Between beta2-adrenoceptor genotypes differences exist both in baseline beta2-agonist induced airway responses as well as in the propensity to develop tolerance during maintenance beta2-agonist therapy. The net differences after two weeks of therapy are, however, of magnitudes that are unlikely to be of clinical significance.

Asthma and athletes: therapy to compete

Asthma presents special challenges to both the athletes who have it and to their health care providers. This article briefly reviews the problem of asthma--especially exercise-induced asthma--in the competitive athlete, and then describes treatments that are effective in controlling asthma. Drug-doping regulations are explained, as is the worldwide impact of drug doping on competitive athletes who have asthma. This review concludes with recommendations for competitive athletes and their health care providers regarding how to deal with asthma in this patient population.

New anti-inflammatory therapies and targets for asthma and chronic obstructive pulmonary disease

Asthma and chronic obstructive pulmonary disease (COPD) are diseases of the airways with an underlying inflammatory component. The prevalence and healthcare burden of asthma and COPD is still rising and is predicted to continue to rise in the foreseeable future. Beta-agonists and corticosteroids form the basis of the therapies available to treat asthma. However, the treatments available for COPD, corticosteroids and anticholinergics, reduce the number and severity of exacerbations, but have a limited effect on slowing the progression of the disease. The inflammatory processes underlying the pathology of asthma have received a great deal of attention and more recently, those underlying COPD have begun to be elucidated. This has resulted in the identification of new targets that will allow the development of novel approaches by the pharmaceutical industry, which will be able to focus its efforts in an attempt to provide new and improved therapies to treat these debilitating diseases. The resultant therapies should impinge on the underlying development of these diseases rather than providing symptomatic relief or palliative treatment alone. This review will outline new targets and novel approaches currently under investigation, which may provide opportunities for novel anti-inflammatory therapeutic interventions that slow or halt disease progression in asthma and COPD.

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

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