Salbutamol-induced increased airway responsiveness to allergen and reduced protection versus methacholine: dose response

Should all asthma patients be switched to single maintenance and reliever therapy?

ABSTRACT

Recent data indicate that overuse of short-acting beta2-agonists (SABAs) results in an increased risk of asthma exacerbations and mortality. The use of inhaled corticosteroid-formoterol as both maintenance and reliever therapy has become a preferred regimen for asthma management. Clinicians should be aware of the pharmacology, dosing, and prescribing considerations regarding the use of budesonide-formoterol as the available combination in the United States.

Small airway dysfunction in asthmatic patients treated with as-needed SABA monotherapy: A perfect storm

BACKGROUND

Short-acting beta agonist (SABA)-only treatment is associated with poor asthma control and adverse clinical outcomes. The importance of small airway dysfunction (SAD) is increasingly recognized in asthma, but less is known in patients using SABA-only therapy. We aimed to investigate the impact of SAD on asthma control in an unselected cohort of 60 adults with physician-diagnosed intermittent asthma treated with as-needed SABA monotherapy.

METHODS

All patients underwent standard spirometry and impulse oscillometry (IOS) at the first visit and were stratified by the presence of SAD defined by IOS (fall in resistance 5-20 Hz [R5-R20]>0.07 kPa × s*L^-1). Univariable and multivariable analyses were used to analyze cross-sectional relationships between clinical variables and SAD.

RESULTS

SAD was present in 73% of the cohort. Compared with patients without SAD, adults with SAD had a higher number of severe exacerbations (65.9% versus 25.0%, p < 0.05), higher use of annual SABA canisters (median (IQR), 3 (1.75-3) versus 1 (1-2), p < 0.001), and significantly less well-controlled asthma (11.7% versus 75.0%, p < 0.001). Spirometry parameters were similar between patients with IOS-defined SAD and those without SAD. The multivariable logistic regression analysis showed that exercise-induced bronchoconstriction symptoms (EIB, odds ratio [OR] 31.18; 95%CI:4.85-365.00) and night awakenings due to asthma (OR 30.30; 95%CI:2.61-1141.00) were independent predictors of SAD, with a high predictive power of the model incorporating these baseline predictors (AUC 0.92).

CONCLUSIONS

EIB and nocturnal symptoms are strong predictors of SAD in asthmatic patients using as-needed SABA-monotherapy, helping to distinguish subjects with SAD among patients with asthma when IOS cannot be performed.

Over-prescription of short-acting beta agonists in the treatment of asthma

BACKGROUND

Despite a clear guideline for asthma medication, excessive use of short-acting β2-agonists (SABAs) is common in clinical practice. Previous research has shown that excessive use of SABAs is associated with poor asthma control.

OBJECTIVE

This study examines current use of asthma medication in primary care and whether excessive use of SABAs is associated with exacerbations.

METHODS

The study design was a retrospective analysis using information from electronical medical records from patients aged 18 and older of five Julius Health Centers located in Utrecht, the Netherlands, in the period of 1 July 2018 through 1 July 2019. Excessive SABA use was defined as ≥400 inhalations per year. An exacerbation was defined as an acute worsening of asthma symptoms with the need for systemic corticosteroids.

RESULTS

A total of 1161 patients were included in the study. Of the patients using SABAs (n = 766), 193 (25%) overused SABAs. Among the patients with inappropriate SABA use (n = 193), 19% had an exacerbation compared with 7% of the appropriate SABA users. For patients using asthma medication the odds of having an exacerbation were 2.9 times higher if they used an inappropriate number of SABAs than if SABAs were used appropriately (odds ratio, 2.897; 95% confidence interval, 1.87-4.48).

CONCLUSIONS

This study shows that overuse of SABAs is still common and that it is associated with asthma exacerbations. It highlights that clinicians need to be aware of inappropriate SABA use as it is a sign of and can even contribute to poor asthma control.

Positioning As-needed Budesonide-Formoterol for Mild Asthma: Effect of Pre-study Treatment in Pooled Analysis of SYGMA 1 and 2

Rationale: The SYGMA (Symbicort Given as Needed in Mild Asthma) studies evaluated the efficacy and safety of as-needed budesonide (BUD)–formoterol (FORM) in patients whose asthma was uncontrolled on as-needed inhaled short-acting bronchodilators (subgroup 1) or controlled on inhaled corticosteroids (ICS) or leukotriene receptor antagonists (subgroup 2).

Objectives: To assess the influence of prestudy treatment in a post hoc analysis of the SYGMA studies.

Methods: In the SYGMA 1 (NCT022149199) and SYGMA 2 (NCT02224157) 52-week, double-blind, randomized, parallel-group studies, 6,735 patients with mild asthma were randomized to as-needed BUD–FORM, low-dose BUD + as-needed terbutaline (BUD maintenance), or as-needed terbutaline (SYGMA 1 only). Exacerbation rates and changes in symptom control and lung function were compared among treatments for both subgroups.

Results: In a pooled analysis of SYGMA 1 and 2, the annual severe exacerbation rate in subgroup 1 was significantly lower with as-needed BUD–FORM (0.08 [95% confidence interval (CI), 0.06–0.10]) than with BUD maintenance (0.10 [95% CI, 0.09–0.13]) (rate ratio [RR], 0.74 [95% CI, 0.56–0.98]; P = 0.03), and similar results were shown in subgroup 2 with BUD–FORM (0.12 [95% CI, 0.10–0.14]) and BUD maintenance (0.10 [95% CI, 0.09–0.13]) (RR, 1.10 [95% CI, 0.86–1.41]; P = 0.44). In SYGMA 1, the annual severe exacerbation rate in both subgroups was significantly lower with as-needed BUD–FORM than with as-needed terbutaline (subgroup 1: RR, 0.34 [95% CI, 0.20–0.58]; P < 0.001; subgroup 2: RR, 0.37 [95% CI, 0.25–0.54]; P < 0.001). The number needed to treat to prevent one severe exacerbation with as-needed BUD–FORM and BUD maintenance versus as-needed terbutaline were 20 and 34 in subgroup 1 and 13 and 12 in subgroup 2, respectively.

Conclusions: These findings suggest that, for patients with mild asthma currently receiving short-acting β₂-agonists alone, as-needed low-dose ICS–FORM should be preferred over maintenance ICS as initial controller treatment. For patients whose asthma is controlled on maintenance low-dose ICS, as-needed BUD–FORM is an alternative to maintenance ICS without the need for daily treatment, and both of these options are safer than switching to short-acting β₂-agonist–only treatment.

Perceptions, attitudes, and behaviors of short-acting beta2 agonist users: an Australian cross-sectional community pharmacy-based study

BACKGROUND

High use of short-acting beta-2-agonist (SABA) medication is a significant problem. Attitudes and perceptions toward asthma of over-the-counter (OTC) reliever users are unknown. The study aimed to describe the asthma attitudes, perceptions, medication knowledge and information gathering behavior of people with asthma with recent high SABA use (i.e. SABA use > twice a week in the last 4 weeks) and compare them to people with asthma with no recent high SABA use.

METHOD

A real-world cross-sectional observational study in Australian community pharmacies was conducted; surveying patients ages ≥ 16 years requesting SABA medication OTC. Data collected included; demographics, medication usage, asthma control, asthma-related perceptions and behaviors. Data were summarized by using descriptive analyses.

RESULTS

375 participants completed the survey, 73.9% were high SABA users. Of the 375, 90.4% reported that their asthma symptoms were controlled or somewhat controlled and 56.0% felt that their asthma was not serious. However, only 17.6%, had controlled asthma according to GINA-defined criteria. High SABA users tended to be more anxious about their asthma and worried about its impact in the future (50.5% vs. 28.6%, p < 0.001). High SABA users were more likely to agree with the statements suggesting that asthma impacted on activities of daily living (46.6% vs. 16.3%, p < 0.001); were socially conscious about their asthma and more likely to feel embarrassed carrying (21.3% vs 9.2%, p = 0.007) and using (29.2% vs 18.4%, p = 0.036) their asthma inhaler.

CONCLUSION

This study revealed the extent of uncontrolled asthma and uncovered an anxious and socially conscious group of OTC SABA users. There is a need to better understand patient perceptions and their relationships to high-SABA use, to ensure targeted educational interventions are developed and implemented.

Understanding reliever overuse in patients purchasing over-the-counter short-acting beta2 agonists: an Australian community pharmacy-based survey

OBJECTIVES

Overuse of asthma relievers is associated with significant adverse consequences. This study aimed to better understand the population purchasing and using short-acting beta agonists (SABA) over the counter (OTC); and compare the demographic, clinical and behavioural characteristics of those who overuse SABA with those who do not.

DESIGN AND SETTING

Real-world cross-sectional observational study in community pharmacy.

PARTICIPANTS

Of 412 participants ≥16 years requesting SABA OTC, 289 were SABA overusers (used SABA more than twice per week in the past 4 weeks).

MAIN OUTCOME MEASURE

Reliever use, Global Initiative for Asthma-defined control, healthcare utilisation, patterns of preventer use.

RESULTS

70.1% of participants were classified as SABA overusers, that is, reporting SABA use more than twice a week within the last 4 weeks, 73.6% reported not using a preventer daily and only 81.6% reported a doctor diagnosis of asthma. SABA overusers were more likely to have moderate-severe nasal symptoms (80.8% vs 63.0%, p<0.001) and a diagnosis of depression (11.1% vs 5.7%, p<0.001), when compared with SABA non-overusers. A higher proportion of SABA overusers had uncontrolled asthma (59.0% vs 15.4%, p<0.001), were more likely to use oral corticosteroids to manage worsening asthma symptoms (26.2% vs 13.5%, p<0.01) and visit the doctor for their asthma in the past 12 months (74.5% vs 62.5%, p<0.01), when compared to SABA non-overusers.

CONCLUSIONS

This study uncovers a hidden population of people who can only be identified in pharmacy with suboptimal asthma, coexisting rhinitis, poor preventer adherence and, in some cases, no asthma diagnosis.

Inappropriate asthma therapy-a tale of two countries: a parallel population-based cohort study

Against recurrent controversies around the safety of short- and long-acting β₂-agonists (SABA and LABA), and the National Review of Asthma Deaths inquiry in the United Kingdom, we investigated the prevalence of inappropriate therapy in asthma. Our study aimed to determine the prevalence of inappropriate use of asthma therapy in the United Kingdom and in France. Two interval, parallel, population-based cohorts (2007 and 2013) were developed in each country by using the UK OPCRD and the French EGB databases. Patients aged 6-40 years were studied over the 12-month period following inclusion, regarding overuse (⩾12 units) of SABA, use of LABA without inhaled corticosteroids (ICS) and ⩾2-fold higher use of LABA compared with that of ICS. Overall, 39,743 UK and 4,910 French patients were included in 2007, and 14,036 and 5,657 patients, respectively, were included in 2013. UK adults were more frequently exposed to SABA overuse compared with those in France in both periods, with an upward trend in the United Kingdom (P<0.05). In 2013, LABA use without ICS occurred in 0.1% and 1.5% of United Kingdom and French adults, respectively. Unbalanced use of LABA relative to ICS became marginal in both countries in 2013. Inappropriate use of therapy was less marked, but present, in children. Inappropriate therapy remains a common issue in asthma. Based on our figures, it may be estimated that >210,000 British and >190,000 French asthmatics aged 6-40 years were inappropriately treated in 2013.

Postnatal overnutrition in mice leads to impaired pulmonary mechanics in response to salbutamol

Obesity increases the risk of respiratory disease, which is associated with airway hyperresponsiveness. Although the molecular underpinnings of this phenomenon are not well established, lung remodeling is known as an important factor in this process and could potentially explain compromised lung functions. In the present study, the obesity was induced by postnatal overnutrition in Swiss mice and we investigated the pulmonary mechanics after aerosolization of saline, methacholine, and salbutamol. The lungs were prepared for morphometric analysis. Obese animals showed bronchoconstriction in response to methacholine, as evidenced by airway and tissue resistance, tissue elastance, and hysteresivity. Salbutamol was effective at recovering the response only for airway resistance but not for tissue mechanics. We suggest that this impaired response in obese mice is related to collapsed alveolar, to inflammatory cells, and to elevated deposition collagen fibers in parenchymal tissue.

Are inhaled longacting β2 agonists detrimental to asthma?

Possible adverse effects of adrenergic bronchodilators in asthma have been the subject of discussion for more than half a century, with recent intense debate about the safety of longacting β agonists (LABAs). In this Debate, we consider the issues of bronchodilator and bronchoprotective tolerance resulting from the frequent use of bronchodilators, which is noted particularly with shortacting drugs, but has also been shown to occur quicker and to a greater extent with LABAs. Increased allergen responsiveness and masking allowing inflammation to increase, while symptoms and lung function remain apparently controlled, have also been observed. Studies in which LABAs were used as monotherapy were associated with increased mortality. However, several studies have shown the benefits of adding LABAs to inhaled corticosteroids (ICS). Meta-analyses of asthma clinical trials involving LABAs showed that, when given with mandatory ICS, LABAs were not associated with an increased risk of death, intubations, or hospital admission for exacerbations when compared with use of the same dose of ICS only. Withdrawal of LABA therapy once symptom control is achieved is often associated with subsequent loss of symptom control. When used for appropriate indications, LABAs should be combined with ICS in one inhaler so that monotherapy is not possible.

Salbutamol tolerance to bronchoprotection: course of onset

BACKGROUND

Regular use of inhaled β-agonist leads to tolerance to its bronchoprotective effect. This occurs within 12 hours with salmeterol and has been documented at 1 week for salbutamol. The course of onset after introduction of salbutamol has not been investigated.

OBJECTIVE

To determine the course of onset of tolerance to the bronchoprotective effect of salbutamol against methacholine.

METHODS

Thirteen individuals with mild asthma completed a randomized, double-blind, placebo-controlled, cross-over study. Each treatment period consisted of 7 twice-daily doses (2 puffs of 100 μg of salbutamol or placebo). Methacholine challenges were conducted 24 hours apart on 4 consecutive days, 10 minutes after the first, third, fifth, and seventh doses. The 2 treatment periods were separated by at least 14 days.

RESULTS

Methacholine provocation concentration that caused a decrease in forced expiratory volume in 1 second of 20% (PC(20)) values during the 4 days of placebo treatment did not significantly differ (analysis of variance P = .79). A single dose of salbutamol shifted the methacholine PC(20) approximately 5-fold from a geometric mean of 2.1 mg/mL to a geometric mean of 10.7 mg/mL. Maximal bronchoprotection after the active treatment occurred on day 2 after the third dose, which was significantly higher than on day 1 after the first dose (P = .04). After the fifth dose the methacholine PC(20) was trending downward, and on day 4 the bronchoprotective effect of salbutamol had significantly decreased from its peak protection (P = .001).

CONCLUSION

The detrimental effects on bronchoprotection after regular use of salbutamol manifest after 5 doses and are significantly reduced from peak protection after 7 doses.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01338311.

Intervention to reduce unnecessary dispensing of short-acting {beta}-agonists in patients with asthma

BACKGROUND

Several clinical studies have suggested that the overuse of short-acting beta-agonists (SABAs) and the underuse of inhaled corticosteroids are prevalent and may compromise patient health and increase the use of scarce health-care resources.

OBJECTIVE

To examine the impact of an intervention designed to reduce SABA metered-dose inhaler (MDI) overdispensing on asthma-related drug and healthcare utilization endpoints in a mail order pharmacy benefit population.

METHODS

Retrospective pre- and postintervention analysis was conducted on all new SABA prescriptions indicating a quantity more than 1 SABA MDI per month and on asthma patients who were continuously enrolled in the Medco Health Solutions prescription benefit program from July 1, 2006, to June, 30, 2007 (preintervention), and July 1, 2007, to June 30, 2008 (postintervention). The intervention involved a written or verbal request to the prescriber to reduce the quantity of SABA MDIs dispensed to less than 1 SABA MDI per month if determined appropriate by the prescriber. Effectiveness of the intervention on asthma-related drug and health-care utilization outcomes were measured in the overall Medco pharmacy population and in asthma patients receiving more than 1 SABA MDI per month.

RESULTS

The percentage of new SABA prescriptions dispensed for more than 1 SABA MDI per month was significantly reduced during year 2 (22.9% vs 9.7%, p < 0.01). Of the 1835 asthma patients who received more than 1 SABA MDI per month in year 1, 1230 (67%) received fewer than 1 SABA MDI per month during year 2. The incidence of asthma-related hospitalizations, emergency department visits, and oral corticosteroid use did not significantly change from year 1 to year 2.

CONCLUSIONS

This analysis shows that an intervention can succeed in reducing the overdispensing of quick-relief medication without compromising asthma control. Further investigation is warranted to better understand the interplay between reduction in excessive SABA use and improved clinical outcomes.

Prolonged bronchoprotection against inhaled methacholine by inhaled BI 1744, a long-acting beta(2)-agonist, in patients with mild asthma

BACKGROUND

Long-acting ss(2)-agonists are an established controller medication in asthma. BI 1744 is a novel L\long-acting ss(2)-agonist with a preclinical profile that suggests 24-hour bronchodilation and bronchoprotection may be achieved.

OBJECTIVE

To examine the bronchoprotective effects of single doses of BI 1744 against methacholine provocation in subjects with mild asthma.

METHODS

Thirty-one subjects with mild asthma were randomized to receive single doses of BI 1744 (2, 5, 10, 20 microg) or placebo on separate days according to a double-blind, 5-way crossover design. Methacholine challenges were performed at 30 minutes and at 4, 8, 24, and 32 hours after each single dose of medication, and the results were expressed as PC(20) FEV(1).

RESULTS

All doses of BI 1744 produced statistically significant increases in the methacholine PC(20) compared with placebo as long as 32 hours. The mean (geometric SEM) methacholine PC(20) 24 hours after dosing with placebo was 1.73 (1.13) mg/mL, which increased after 2 microg to 3.86 (1.14) mg/mL, after 5 microg to 5.67 (1.14) mg/mL, after 10 microg to 9.42 (1.13) mg/mL, and after 20 microg to 13.71 (1.14) mg/mL (all P < .0001). After 32 hours, the methacholine PC(20) value remained significantly increased for all doses. No safety or tolerability concerns were identified.

CONCLUSION

BI 1744 provides significant bronchoprotection against inhaled methacholine for up to 32 hours after single-dose administration.

Getting to the heart of asthma: can "beta blockers" be useful to treat asthma?

beta(2)-adrenoceptor agonists are the mainstay for the acute symptomatic treatment of asthma and provide effective bronchoprotection to a wide range of bronchoconstrictor agents. However, over the past 4 decades there has been a continuing debate concerning whether regular chronic treatment with these drugs may be doing more harm than good. The FDA's recent decision to add black box warnings concerning the regular use of salmeterol- and formoterol-containing compounds, as well as their decision not to recommend agents containing long-acting beta(2)-adrenoceptor agonists as first-line therapy, seems to confirm the concerns regarding the regular use of the long-acting beta(2)-adrenoceptor agonists. A similar debate arose in the late 1980s concerning the use of beta-adrenoceptor agonists in the treatment of heart failure. In this disease, short-term use of beta agonists is associated with increased cardiac index and stroke volume, yet their long-term use is associated with increased morbidity and mortality. Moreover, certain beta blockers that are initially detrimental when used short term are now considered beneficial in the treatment of this disease when used chronically. Here, there is a parallel, as beta blockers are contraindicated in patients with asthma but the use of beta blockers chronically has never been evaluated. This begs the question of whether a similar paradigm shift is applicable in the treatment of asthma and whether under certain circumstances the long-term use of certain beta blockers may be useful in the treatment of this disease.

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.

Clinical concerns with inhaled beta2-agonists: adult asthma

Inhaled beta2-agonists, when used regularly, cause subtle but significant worsening of asthma control. Overuse of inhaled beta2-agonists is associated with increased risk of death from asthma in a dose-response fashion. beta2-Agonists enhance airway responses to allergens, including induced airway hyperresponsiveness and induced airway inflammation. This is a plausible explanation for beta2-agonist-worsened asthma control. These direct effects of inhaled beta2-agonists, including increased airway response to allergen, tolerance, etc., may partially explain the association of overuse with asthma death. However, it is probable that the major reason for the association of beta2-agonists overuse and asthma mortality is an indirect effect. Inhaled beta2-agonists are effective relievers and preventers of bronchoconstriction and asthma symptoms but fail to treat the underlying pathogenesis, namely the airway inflammation. Thus, overuse may mask the true asthma severity and result in both an underappreciation and undertreatment of the disease. This would provide a rational explanation for the relationship of inhaled beta2-agonist use and mortality and also would fit the dose-response pattern. Inhaled beta2-agonists should be used exclusively as needed for relief of symptoms and their requirement should be infrequent: the need for excessive doses of beta2-agonists provides a useful marker of asthma (lack of) control.

(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?"

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.

Clinical practice guidelines: medical follow-up of patients with asthma--adults and adolescents

The follow-up of patients with asthma should focus on asthma control (disease course over a number of weeks).

As-needed inhaled beta2-adrenoceptor agonists in moderate-to-severe asthma: current recommendations

Intermediate-acting inhaled beta2-agonists (e.g. albuterol [salbutamol]), once recommended for round-the-clock bronchodilation, are now recommended to be used exclusively as-needed. Guidelines advise that asthma should be controlled with anti-inflammatory therapeutic strategies so that the as-needed requirement for inhaled beta2-agonists should be infrequent; ideally less than several times per week, up to once a day for exercise, and none at night. These recommendations are based upon the recognition that asthma is primarily an inflammatory condition and that the major thrust of therapy should be anti-inflammatory, including environmental control and administration of inhaled corticosteroids (ICS), leukotriene-receptor antagonists, and possibly oral theophylline and inhaled cromones; the cromones include cromolyn sodium (sodium cromogylcate) and nedocromil. While this is the primary rationale behind the as-needed infrequent prescription of the inhaled beta2-agonist paradigm, there are a number of detrimental effects that can be seen with regularly scheduled (or frequent as-needed) use of inhaled beta2-agonists. These include tolerance to the bronchodilator and particularly the bronchoprotective effects, increased airway responsiveness to allergen, worsened asthma control, and, probably most importantly, over-reliance on an excellent symptom reliever leading to undertreatment. Any or all of these could be responsible for the demonstrated dose-response relationship between inhaled beta2-agonist overuse and death from asthma. Several controlled clinical trials, which have included many patients with at least moderately severe asthma, have failed to demonstrate any obvious advantage to the regular scheduled use of inhaled beta2-agonists compared with as-needed inhaled beta2-agonists. On the other hand, despite no obvious advantage, regular use of albuterol 1000-1200 microg/day appears to be well tolerated and reasonably safe. When asthma is treated using an as-needed, infrequent inhaled beta2-agonist, the requirements for beta2-agonists become a useful marker of whether or not the asthma is adequately controlled. When inhaled beta2-agonists are required inordinately frequently (i.e. when asthma is not adequately controlled), after ensuring compliance with ICS, the most common strategy is to add one of the long-acting inhaled beta2-agonists twice daily. On the basis of the available evidence, the as-needed intermediate-acting inhaled beta2-agonist therapeutic strategy appears appropriate for patients with moderate-to-severe asthma.

Influence of epithelium and isoprenaline incubation on responsiveness of guinea-pig trachea to methacholine

There are reports regarding harmful effect of long-term use of beta2-agonist drugs on asthma severity and airway responsiveness. In the present study, the responses of guinea pig trachea with intact and denuded epithelium (groups 1 and 2, n = 10) to methacholine as EC50 were measured in tissues nonincubated or incubated with 10 mumol/l isoprenaline during the resting period. The same protocol was performed in groups 3 and 4 (n = 5 for each group) with an additional 30 min rest time after isoprenaline incubation. The response of trachea with denuded epithelium (groups 2 and 4) to methacholine was significantly higher than that with intact epithelium both in incubated and nonincubated conditions (groups 1 and 3, p < 0.05 to p < 0.001). Incubation with isoprenaline caused a significant reduction in the tracheal response to methacholine in both the denuded groups (p < 0.005 and p < 0.001) and intact epithelium groups (p < 0.005 for both cases). The reduction in tracheal responsiveness to methacholine due to incubation in epithelium denuded trachea (groups 2 and 4) was nonsignificantly greater than that of intact epithelium tissues. There was no difference between groups 3 and 4 with those of groups 1 and 2 in both incubated and non incubated conditions. The maximum contractility response to methacholine was not different between tracheal chains with denuded and intact epithelium and did not change due to incubation with isoprenaline. The results of this study indicate reduction of tracheal response to methacholine due to incubation of tissues with isoprenaline, which was relatively more pronounced in epithelium denuded trachea.

Levalbuterol hydrochloride

Racemic salbutamol (racemic albuterol) ameliorates symptoms of asthma by activating beta-adrenoceptors on nerve, smooth muscle and inflammatory cells within the airways. Racemic salbutamol comprises equal proportions of 2 isomers: (S)-salbutamol and (R)-salbutamol, with the latter being exclusively responsible for activation of beta-adrenoceptors. Accordingly, within racemic salbutamol it is (R)-salbutamol that efficiently relieves obstruction of asthmatic airways and affords highly effective protection from bronchoconstrictor stimuli, including allergens. During regular use of racemic salbutamol, there is a progressive decline of protective efficacy and a corresponding intensification of airway responsiveness. This decline is largely absent during regular use of (R)-salbutamol. Consequently, bronchodilator responses to sub-maximal doses of (R)-salbutamol exceed responses to the equivalent dose of (R)-salbutamol given as the racemate. For example, in asthmatics with baseline FEVs <or= 60%, 1.25 mg of nebulised (R)-salbutamol achieved a maximal 52% change in FEV while 2.5 mg of racemic salbutamol only achieved a 38% change in FEV. Since extrapulmonary effects (e.g., tremor, heart rate) of beta agonists are related to dose and limit the use of beta agonist therapy, (R)-salbutamol at 0.63 mg provides uncompromised efficacy with marked reduction of side-effects. In addition to quantitative differences, the constituent isomers of salbutamol also exhibit qualitative differences. Thus, (R)-salbutamol inhibits activation of human eosinophils in vitro whereas, under the same conditions and concentrations, (S)-salbutamol augments activation of these cells. This property of (S)-salbutamol may explain why eosinophilia in induced sputum from subjects with allergic asthma is increased by regular use of racemic salbutamol. Similarly, the capacity of (R)-salbutamol to suppress hyperresponsiveness of the airways can be contrasted with the capacity of (S)-salbutamol to intensify hyperresponsiveness. This action of (S)-salbutamol would explain why regular use of racemic salbutamol intensifies the bronchoconstrictor response to antigen in subjects with allergic asthma. Taken together, these findings imply that replacement of racemic salbutamol by (R)-salbutamol will diminish, or even eliminate, the anomalous actions that have curtailed the efficacy of racemic salbutamol. Pharmacokinetically, (R)-salbutamol exhibits near absolute conformational stability (i.e., no conversion to (S)-salbutamol). If in vitro anti-inflammatory actions of (R)-salbutamol are also manifest in asthmatic airways, (R)-salbutamol could provide a novel approach to asthma therapy which combines bronchodilation and bronchoprotection with anti-inflammatory efficacy.

Effect of reproterol either alone or combined with disodium cromoglycate on airway responsiveness to methacholine

Regular use of inhaled beta2-agonists might lead to tolerance as reflected in a loss of bronchoprotection. In vitro-data suggest that this might be prevented by disodium cromoglycate (DSCG). Therefore, we studied the effect of the beta2-agonist reproterol in combination with DSCG. In a cross-over design, 19 subjects with airway hyperresponsiveness inhaled either placebo, 1mg reproterol, 2 mg DSCG, or 1mg reproterol plus 2 mg DSCG 4x daily over 2 weeks. Treatment periods were separated by > or = 7 days. Before and at the end of periods, lung function and methacholine responsiveness were determined in the morning, and 6h later the bronchodilator effect and the protection against methacholine-induced bronchoconstriction. Reproterol or DSCG or their combination did not exert detrimental effects on lung function, airway responsiveness, or bronchodilator capacity. However, bronchoprotection was significantly reduced (p < 0.05) after treatment with placebo, reproterol or reproterol plus DSCG, the respective changes being 0.59, 0.96 and 1.37 doubling concentrations. All changes were small as compared to intraindividual variability. In this model all treatments except with DSCG caused a significant but small loss of protection against methacholine-induced bronchoconstriction. Thus, tolerance was not prevented by 2 weeks of additional treatment with DSCG, in contrast to in vitro findings.

Paradoxal effect of salbutamol in an in vitro model of bronchoprotection

Salbutamol-induced hyperresponsiveness to acetylcholine was investigated in human and guinea-pig isolated airways and cultured human airway smooth muscle cells. Salbutamol (10(-7)-10(-5) m) inhibited contractions induced by low concentrations of acetylcholine (10(-8)-10(-7) m) but potentiated contractions induced by higher concentrations of acetylcholine (10(-5)-10(-3) m). Pretreatment with the calcium channel antagonist nicardipine suppressed salbutamol-induced hyperresponse. Stimulation of cultured human airway smooth muscle cells with salbutamol (10(-6) m) amplified intracellular calcium concentration rise induced by acetylcholine (10(-5) m). Propranolol (10(-7) m), a beta1- and beta2-adrenoceptor antagonist, and ICI 118551 (10(-7)-10(-6) m), a beta2-adrenoceptor antagonist, suppressed the inhibitory effect of salbutamol but did not inhibit the hyperresponse on high concentrations of acetylcholine. In contrast, higher concentration of propranolol (10(-6) m) inhibited salbutamol-induced hyperreactivity. Effects of salbutamol were not affected by atenolol, a beta1-adrenoceptor blocker. Salbutamol-induced hyperresponsiveness is mediated through a mechanism involving calcium channel activation.

Adverse effects of short-acting beta-agonists: potential impact when anti-inflammatory therapy is inadequate

BACKGROUND

Short-acting beta-agonists (SABAs) are associated with reduced lung function and increased bronchial hyper-responsiveness. Earlier studies have failed to show that these changes are clinically important when SABAs are taken regularly in modest doses. However, some patients use SABAs to excess, especially with deteriorating asthma. Our aim was to establish whether adverse effects of SABAs are greater at higher than normal doses and after withdrawing inhaled corticosteroid (ICS) therapy.

METHODOLOGY

This was a randomized controlled study. The treatments were salbutamol/ipratropium 100 microg/20 microg/puff or ipratropium 20 microg/puff, each 12 puffs daily. Phase 1 was of 2 weeks duration. During phase 2 ICS were withdrawn until loss of control (LOC) occurred.

RESULTS

During phase 1 the mean FEV1 fell by 9.3% with salbutamol (0.26 L; 95% C.I. 0.13, 0.39), but by only 1.6% with ipratropium (0.05 L; 95% C.I. -0.06, 0.16; P = 0.006). During phase 2 FEV1 fell by a further 18.9% with salbutamol (0.54 L; 95% C.I. 0.39, 0.69), but by only 10.5% (0.33 L; 95% C.I. 0.17, 0.49; P = 0.032) with ipratropium. Time to LOC was significantly shorter with salbutamol (8.9 days) compared to ipratropium (16.8 days; P = 0.03).

CONCLUSION

Adverse changes in lung function with SABA appear to be greater with higher doses and increasing airway inflammation. This highlights the risks of excessive SABA use in patients who neglect ICS therapy and/or who rely on 'relievers'.

Preserved bronchial dilatation after salbutamol does not guarantee protection against bronchial hyperresponsiveness

Racemic salbutamol, a beta2-adrenoceptor agonist used for dilatation of airways, has recently been shown to induce lessened relaxation of bronchial smooth muscle and partial loss of bronchoprotection, seen as increased hyperresponsiveness, after regular treatment. The racemate undergoes stereo-selective disposition, giving higher plasma levels of S-salbutamol than that of bronchodilating R-salbutamol, thus raising S : R ratios after repeated administration. Our aim was to evaluate whether increased bronchial hyperresponsiveness (BHR) could be found even after 1 day of repeated salbutamol inhalations, with beta2-receptor-induced bronchial smooth muscle relaxation remaining and whether this would be associated with plasma levels of either enantiomer. Fifteen patients with stable asthma, aged 19-54 years, were included in a randomized, cross-over study. An indirect bronchial challenge method was used [voluntary isocapnic hyperventilation of cold air (IHCA)], and airway condition tested by means of impulse oscillometry. Racemic salbutamol was inhaled three times during a 6-h period. IHCA was performed and plasma concentrations of enantiomers were measured 4 h after the last dose. Tests were also performed without preceding drug treatment. beta2-Agonist-produced bronchial dilatation and protection persisted in the majority of the 15 patients 4 h after repeated inhalations of salbutamol during 1 day. In only two of the 15 patients we could trace increased BHR after salbutamol. Neither dilatation nor protection could be linked to plasma levels of either R- or S-salbutamol. The underlying mechanisms of BHR remain unknown and are dissociated from beta2-receptor-mediated dilatation.

Adverse effects of beta-agonists

Short-acting beta-adrenergic receptor agonists have pharmacologically predictable dose-related and potency-related adverse effects, including tachycardia and tremor, and they also affect serum potassium and glucose. These effects all show tolerance with continued exposure. The potential for arrhythmia is increased by comorbidity and hypoxemia. Nonpharmacologically predictable effects include airway hyperresponsiveness to nonspecific and specific stimuli, including allergen and exercise, and increased airway inflammation. Genetic variants of the beta-adrenergic receptor alter susceptibility to adverse effects of beta-agonists on airway function. The impact of the enantiomers of beta-agonists on adverse effects remains unclear. The two epidemics of asthma death among young people were temporally associated with introduction of potent short-acting beta-agonists (isoproterenol and fenoterol) and appear to be related to adverse effects of these drugs on airway function and airway hyperresponsiveness rather than to cardiotoxicity. Compared with short-acting agents, long-acting beta-agonists show similar but less pronounced pharmacologically predictable effects, and they have not been shown to increase airway hyperresponsiveness in adults. Postmarketing surveillance studies have not suggested significant adverse effects of long-acting beta-agonists on morbidity and mortality.

Oral salbutamol decreases IL-12 in patients with secondary progressive multiple sclerosis

IL-12 is a key cytokine for Th1 cell development and may be important in the pathogenesis of multiple sclerosis (MS). The beta2-agonist salbutamol is known to decrease IL-12 production in monocytes of normal individuals through increased intracellular cAMP. In a prospective open-label study, we investigated by flow cytometry the effect of a 2-week long oral salbutamol treatment on monocyte IL-12 production in 21 secondary progressive MS patients. Baseline IL-12 production was higher in patients than in healthy controls. The treatment induced a significant decrease in the percentage of IL-12-producing monocytes and dendritic cells that lasted up to 1 week after treatment interruption. This first report on the use of salbutamol in MS shows that this drug has immunomodulatory properties both in vivo and in vitro, and may be beneficial in the treatment of MS.

Regular inhaled salbutamol : effect on airway responsiveness to methacholine and adenosine 5'-monophosphate and tolerance to bronchoprotection

OBJECTIVE

Regular treatment with inhaled beta(2)-agonists increases airway responsiveness consistently to indirect bronchoconstrictors (allergen, exercise, hypertonic saline solution, etc) and inconsistently to direct bronchoconstrictors (histamine, methacholine). Studies demonstrating tolerance to beta(2)-agonist bronchoprotection against the indirect bronchoconstrictor adenosine 5'-monophosphate (AMP) have not examined changes in baseline AMP responsiveness. This study assessed the effect of regular salbutamol on AMP and methacholine responsiveness and on tolerance to bronchoprotection.

DESIGN

Double-blind, randomized, crossover study.

SETTING

University hospital bronchoprovocation laboratory.

PATIENTS

Fourteen atopic asthmatic subjects with FEV(1) > 65% predicted, and methacholine provocative concentration causing a 20% fall in FEV(1) (PC(20)) < 8 mg/mL.

INTERVENTIONS

Salbutamol, 100 microg, and placebo inhalers, two puffs qid, each for 10 days.

MEASUREMENTS

Methacholine PC(20) and AMP PC(20) measured 12 h after blinded inhaler after each treatment period. Methacholine PC(20) and AMP PC(20) repeated 10 min after salbutamol, 200 microg (eight subjects).

RESULTS

There was no difference between placebo and salbutamol treatment in geometric mean methacholine PC(20) (0.85 mg/mL vs 0.82 mg/mL, p = 0.86) or AMP PC(20) (22 mg/mL vs 17.4 mg/mL, p = 0.21; n = 14). The acute bronchoprotective effect of salbutamol was greater vs. AMP than vs methacholine (5.1 doubling concentrations vs. 3.5 doubling concentrations, p = 0.06) and loss of protective effect of salbutamol (mean +/- SD) was greater vs AMP than vs. methacholine (2.4 +/- 0.33 doubling concentration loss vs 0.8 +/- 0.21 doubling concentration loss, p = 0.008; n = 8).

CONCLUSION

Regular salbutamol (mean +/- SD) treatment did not enhance airway responsiveness to either the indirect bronchoconstrictor AMP or the direct bronchoconstrictor methacholine. Compared to its effect on methacholine, salbutamol had a greater acute protective effect vs AMP and produced greater loss of protection vs AMP when used regularly.

Mast cell tryptase release and asthmatic responses to allergen increase with regular use of salbutamol

BACKGROUND

Increased asthmatic responses to allergen, both early and late, have been demonstrated after regular use of beta(2)-agonists in as few as 7 days. Desensitization of beta(2)-adrenergic receptors on airway mast cells may contribute to this effect by allowing greater release of mast cell mediator on allergen-induced degranulation. Tryptase released from lung mast cells can be measured in serum 1 hour after allergen challenge and serves as a marker of mast cell degranulation.

OBJECTIVE

To examine the effect of regular treatment with salbutamol, a beta(2)-agonist, on mast cell mediator release after allergen challenge and its influence on the early asthmatic response (EAR) and the late allergic response, we measured the EAR, serum tryptase levels, the 7-hour FEV(1), and sputum tryptase levels and cell profiles.

METHODS

We conducted a placebo-controlled, double-blind, randomized cross-over comparison of treatments for 10 days with either a salbutamol metered-dose inhaler (100 microgram, 2 puffs 4 times daily) or a matched placebo inhaler with at least a 7-day washout between treatments. Atopic subjects (n = 14) with mild-to-moderate asthma performed same-dose allergen inhalation tests after both treatments 12 to 15 hours after the last dose of study inhaler. Baseline and 7-hour FEV(1) and the EAR to allergen were measured by using spirometry; venous blood was drawn at 1 hour for analysis of serum tryptase; and sputum was induced and collected at 1 and 7 hours.

RESULTS

Salbutamol treatment resulted in a significantly greater EAR (20% +/- 1.6% [SEM] vs 15% +/- 2.1%; P =.047); increased 1-hour serum tryptase levels (9.09 +/- 1.57 vs 7.52 +/- 1.12 microgram/L; P =. 011); increased proportions of eosinophils in the 7-hour sputum sample (39.1% +/- 5.1% vs 28.4% +/- 4.4%; P <.05); increased proportion of metachromatic cells in the 7-hour sputum sample (4.4% +/- 1.1% vs 2.2% +/- 0.6%; P =.032); and lower 7-hour FEV(1) (2.77 +/- 0.18 vs 2.97 +/- 0.20 L; P =.014). Baseline FEV(1) was not significantly different after salbutamol treatment compared with values after placebo treatment (2.90 +/- 0.20 vs 3.00 +/- 0.19 L; P =.11).

CONCLUSION

Regular 10-day treatment with salbutamol increases the allergen-induced release of mediator from airway mast cells, and this is reflected in an increased EAR to allergen. Late-phase responses to allergen were also enhanced, as demonstrated by decreased 7-hour FEV(1) and increased eosinophilia and percentage of metachromatic cells in the 7-hour sputum sample. Increased allergen-induced mast cell degranulation could, in part, explain the increased asthmatic responses to allergen after beta(2)-agonist treatment and could contribute to the deterioration of asthma control that is associated with regular use of beta(2)-agonist by potentiating allergic inflammation.

Effects of terbutaline and budesonide on sputum cells and bronchial hyperresponsiveness in asthma

Previous studies have shown that the regular administration of short acting beta-agonists can be associated with adverse effects on airway caliber and bronchial hyperresponsiveness (BHR) and that this may occur through a proinflammatory mechanism. The aim was to explore possible adverse effects of high-dose beta-agonist therapy and to assess any adverse interaction with corticosteroids. We undertook a randomized, crossover study to investigate the effects of 6 wk of treatment with regular terbutaline (1 mg four times a day), regular budesonide (400 microg twice a day), combined treatment, and placebo in subjects with mild to moderate asthma. Major endpoints were PD(15) saline, PD(20) methacholine, and induced sputum differential cell counts. Thirty-four subjects were randomized and 28 completed the study. PD(15) saline decreased on terbutaline alone compared with placebo treatment and on combined treatment compared with budesonide alone (mean fold decrease of 0.57 [95% CI = 0.36, 0.90] and 0.65 [95% CI = 0.43, 0.97], respectively). PD(20) methacholine was not affected by the use of terbutaline either alone or in combination with budesonide. The percentage of eosinophils in induced sputum increased during terbutaline treatment alone compared with placebo (median 8.3% versus 4.4%, p = 0.049). The addition of terbutaline to budesonide did not affect the percentage of eosinophils compared with budesonide treatment alone. These findings support the hypothesis that short-acting beta-agonists have a permissive effect on airway inflammation and that when used in high dose there may be an unfavorable interaction with inhaled corticosteroids.

New millennium bronchodilators for asthma: single-isomer beta agonists

Racemic beta2 agonists are composed of a 50:50 mixture of R and S isomers. The R isomer exhibits virtually all the bronchodilation, whereas the S isomers are generally considered inert. However, (S)-albuterol was shown to enhance bronchial reactivity to methacholine, eosinophil activation, and histamine-induced influx of fluid, proteins, and neutrophils into the airspaces. Actions such as these may compress the potency and foreshorten the duration of (R)-albuterol. Accordingly, pure (R)-albuterol provides bronchodilation at lower doses than racemate, allowing for fewer beta-adrenergic-mediated side effects. In addition, differential metabolism may allow for the progressive accumulation of (S)-albuterol. This logic is applicable to long-acting beta2 agonists: the therapeutically active (R,R)-formoterol is currently being developed in the United States, and preliminary results suggest rapid improvements in FEV1 with up to 24-hour duration of action. These combined observations with the R isomers of beta2 agonists suggest that potential improvements in therapeutic indices can be achieved with isomerically pure versions of existing racemic drugs.

Atopic diseases and upper respiratory infections

This article reviews information on the topics of asthma, allergic rhinitis, atopic dermatitis, food allergy, and upper respiratory infections. The asthma section includes a review of inhaled steroids and their potential side effects. New findings on the pathogenesis, triggers, and therapies of atopic dermatitis and new insights into food hypersensitivity reactions are presented. Recent publications in the areas of allergic rhinoconjunctivitis and upper respiratory infections are also reviewed.

Comparison of the relative efficacy of formoterol and salmeterol in asthmatic patients

Studies performed on airway smooth muscle in vitro have indicated that salmeterol is a partial agonist on the beta2-receptor in comparison to formoterol. In the present study we evaluated whether these pharmacological differences between salmeterol and formoterol also are applicable to asthmatic patients. The protective effects by increasing cumulative doses of formoterol (12, 60, 120 micrograms) and salmeterol (50, 250, 500 micrograms) on methacholine-induced bronchoconstriction were evaluated in a double-blind, crossover, placebo-controlled design. Patients were regularly treated with salbutamol 200 micrograms twice daily during the study period, to avoid variability in beta2-adrenoceptor tolerance. S-potassium, heart rate corrected Q-T interval (Q-Tc), and tremor score were followed as measures of systemic effects. Formoterol dose-dependently protected against methacholine responsiveness (4.6 doubling doses after 120 micrograms). Salmeterol, however, showed a flatter dose-response curve, and a significantly weaker maximal protective effect (2.8 doubling doses after 250 micrograms). Formoterol caused a significantly higher tremor score and a larger drop in S-potassium than salmeterol at the highest doses. These data show that salmeterol is a partial agonist on the beta2-receptor in relation to formoterol in human airways in vivo. Further studies are required to document the clinical consequences of this finding, for example in severe asthmatic patients.

Proventil HFA and ventolin have similar safety profiles during regular use

OBJECTIVE

As a secondary objective to a long-term study evaluating the bronchodilator effectiveness of Proventil HFA (albuterol), to assess the safety of Proventil HFA, Ventolin, and hydrofluoroalkane 134a (HFA-134a) placebo over 12 weeks of regular dosing.

DESIGN

Randomized, double-blind, double-dummy parallel group, placebo-controlled, multicenter trial of asthmatics requiring inhaled beta-adrenergic bronchodilators for symptom control.

INTERVENTIONS

Treatment with Proventil HFA, Ventolin, or HFA-134a placebo, qid, for 12 weeks.

MEASUREMENTS

Adverse events were reviewed at biweekly clinic visits. Between clinic visits, patients recorded morning and evening peak expiratory flow (PEF), asthma symptom and nighttime asthma sleep disturbance scores, and use of rescue beta-adrenergic bronchodilator on diary cards daily. Investigators provided a global assessment of asthma control at weeks 0, 4, 8, and 12. Vital signs were recorded over 6 h after dosing with study drug at weeks 0, 4, 8, and 12. Standard laboratory tests, CBC count, serum chemistries, and urinalysis were obtained at study start and end.

RESULTS

Adverse event reporting rates were similar for the three treatment groups. The morning PEF tended to be lower for the Proventil HFA and Ventolin groups than the HFA-134a placebo group, but the evening PEF tended to be higher for the active treatment groups. Daytime asthma symptom scores tended to be lower (better) with active treatment than placebo, but nighttime asthma sleep disturbance scores were similar for all three treatment groups. Use of Ventolin Rotacaps as rescue medication was significantly greater for the HFA-134a placebo group than the Proventil HFA and Ventolin groups. Diary card data did not change within groups over time. Investigator global assessments of asthma scores clustered between fair and good for all three treatment groups throughout the study. Changes in heart rate and BP were small after dosing with study drug and tended to be similar for the active treatments and HFA-134a placebo groups. No clinically meaningful changes in results of standard laboratory tests were found in any treatment group during this study.

CONCLUSIONS

Proventil HFA had a similar safety profile as Ventolin during regular use. A dosage of 16 puffs per day of propellant HFA-134a was well tolerated by asthmatics. Regular use of either Proventil HFA or Ventolin did not cause asthma control to deteriorate.

Tolerance to the bronchoprotective effect of salmeterol 12 hours after starting twice daily treatment

BACKGROUND

Regular use of salmeterol has been associated with reduced bronchoprotective effect against methacholine as early as 24 hours after initiating treatment.

OBJECTIVE

To determine whether loss of the bronchoprotective effect measured one hour after salmeterol could be demonstrated 12 hours following one previous dose.

METHODS

Ten subjects with stable, mild asthma were enrolled in a randomized, placebo-controlled, double-blind, crossover study comparing two 2-dose treatment periods: (1) blinded salmeterol 50 microg inhaled at bedtime, followed by unblinded salmeterol 50 microg inhaled 12 hours later and (2) blinded placebo inhaled at bedtime, followed by unblinded salmeterol 50 microg inhaled 12 hours later. The methacholine PC20 was measured one hour after the morning salmeterol; FEV1 was measured just prior to the morning salmeterol dose and at the start of the methacholine inhalation test.

RESULTS

The mean log methacholine PC20 recorded one hour after a single dose of salmeterol (1.20 +/- 0.17 SE) was significantly higher than the mean log methacholine PC20 recorded after two doses of salmeterol at 12-hour intervals (1.00 +/- 0.16 SE; P = .024). The mean FEV1 12 hours after salmeterol was significantly higher than the mean FEV1 recorded 12 hours after placebo (P = .0017), however, there was no significant difference between the FEV1 recordings one hour after the two unblinded doses of salmeterol.

CONCLUSIONS

Tolerance to the bronchoprotective effect of salmeterol against methacholine induced bronchoconstriction occurs extremely quickly as it is evident 12 hours after starting twice daily treatment.

Beta2-agonists prevent Th1 development by selective inhibition of interleukin 12

Interleukin 12 (IL-12) plays a central role in the immune system by skewing the immune response towards T helper 1 (Th1) type responses which are characterized by high interferon-gamma and low IL-4 production. In this report we present evidence that beta2-agonists inhibit IL-12 production by both human monocytes in response to lipopolysaccharide (LPS) and dendritic cells stimulated via CD40. Inhibition of IL-12 production is selective, as other cytokines produced by monocytes are unaffected. IL-12 inhibition is dependent on beta2-adrenoceptor stimulation and correlates with increased levels of intracellular cAMP. In conjunction with their ability to suppress IL-12 production, when beta2-agonists are added at priming of neonatal T lymphocytes, they inhibit the development of Th1-type cells, while promoting T helper 2 (Th2) cell differentiation. Further, the in vivo administration of a therapeutic dose of salbutamol results in the selective inhibition of IL-12 production by whole blood lymphocytes stimulated in vitro with LPS. These findings provide new insight into the immunological consequences of the clinical use of beta2-agonists and may suggest new approaches for the treatment of Th1-mediated diseases.