Confounding by severity does not explain the association between fenoterol and asthma death

An update on the safety of long-acting beta-agonists in asthma patients using inhaled corticosteroids

IMPORTANCE OF THE FIELD

Pooled trial data have shown that long-acting beta-agonists increase the risk for asthma hospitalizations and deaths by two to fourfold compared with placebo. Until recently, it was unclear whether concomitant inhaled corticosteroids (ICSs) could eliminate this risk.

AREAS COVERED IN THIS REVIEW

This review summarizes the available data on the safety of long-acting beta-agonist use in asthma, with and without concomitant ICSs. The results from an updated meta-analysis are presented, with data through December 2008.

WHAT THE READER WILL GAIN

In pooled trial data, catastrophic asthma events (defined as asthma-related intubation or death) were increased fourfold for concomitant treatment with long-acting beta-agonists and ICSs compared with corticosteroids alone (odds ratio 3.7; 95% CI 1.4 - 9.6). It is estimated that the addition of long-acting beta-agonists to ICS therapy is associated with an absolute increase of one catastrophic event per 1500 patient-years.

TAKE HOME MESSAGE

When the available trial data are pooled together, it is clear that long-acting beta-agonists significantly increase the risk for asthma-related intubations and deaths, even when used in a controlled fashion with concomitant ICSs. Clinical guidelines should readdress the role long-acting beta-agonists have in the management of asthma.

Long-acting beta-agonists and asthma death: how useful are different study designs to evaluate the potential association?

BACKGROUND AND OBJECTIVE

There is uncertainty whether long-acting beta-agonist (LABA) drugs may increase the risk of asthma mortality. This uncertainty is partly due to the difficulty in estimating the risk of rare adverse outcomes. The aim of this paper is to consider the utility of three approaches to determine the magnitude and statistical significance of this potential association.

METHODS

Using a death rate of 9 per 10,000 subjects with asthma, derived from a meta-analysis of randomized controlled trials (RCTs) of formoterol, power calculations for a single RCT, a case-control study, and a meta-analysis of RCTs were determined.

RESULTS

For each study design, the number of subjects and events required to have adequate statistical power to detect a 1.5- and 2.0-fold increased risk of death were calculated. For a single RCT, or meta-analyses of RCTs, very large sample sizes are required. In contrast, case-control methodology represents a realistic method of estimating the risk of rare serious adverse events.

CONCLUSIONS

Major practical limitations exist in the use of RCTs to determine the potential risk of death with LABAs in the treatment of asthma. Case-control methodology may be more effective in establishing causation; however, if selection bias occurs, estimates of risk may be inaccurate.

Therapeutic management of allergic diseases

Allergic diseases are characterized by the activation of inflammatory cells and by a massive release of mediators. The aim of this chapter was to describe succinctly the modes of action, indications, and side effects of the major antiallergic and antiasthmatic drugs. When considering the ideal pharmacokinetic characteristics of a drug, a poorly metabolized drug may confer a lower variability in plasma concentrations and metabolism-based drug interactions, although poorly metabolized drugs may be prone to transporter-based disposition and interactions. The ideal pharmacological properties of a drug include high binding affinity, high selectivity, and appropriate association and dissociation rates. Finally, from a patient perspective, the frequency and route of administration are important considerations for ease of use.

Antidepressant adequacy and work status among medicaid enrollees with disabilities: a restriction-based, propensity score-adjusted analysis

Abstract This cross-sectional study of adult survey respondents with disability and depression (n = 199) enrolled in Massachusetts' Medicaid program examined the association of adequately or inadequately prescribed antidepressant treatment and self-reported work status using conditional logistic regression, controlling for age, gender, race, marital status, education, receipt of SSI/SSDI, self-reported disabling condition, and health status. Confounding by severity was addressed by two methods: restriction of our sample and subsequent stratification by propensity score. Individuals receiving adequate antidepressant treatment had an increased odds of working compared to individuals receiving inadequate treatment, both in analyses in which restriction was used to limit confounding (OR = 3.45, 95% CI = 1.15-10.32, P < .03), and in analyses which combined restriction with adjustment by propensity score stratification (OR = 3.04, 95% CI = 1.01-9.62, P < .05). Among this sample of Medicaid enrollees with disability and depression, those receiving adequate antidepressant treatment were significantly more likely to report working.

Asthma

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

Adverse effects of beta-agonists: are they clinically relevant?

Inhaled beta(2)-adrenoceptor agonists (beta(2)-agonists) are the most commonly used asthma medications in many Western countries. Minor adverse effects such as palpitations, tremor, headache and metabolic effects are predictable and dose related. Time series studies suggested an association between the relatively nonselective beta-agonist fenoterol and asthma deaths. Three case-control studies confirmed that among patients prescribed fenoterol, the risk of death was significantly elevated even after controlling for the severity of asthma. The Saskatchewan study not only found an increased risk of death among patients dispensed fenoterol, but also suggested this might be a class effect of beta(2)-agonists. However, in subsequent studies, the long-acting beta(2)-agonist salmeterol was not associated with increased asthma mortality. In a case-control study blood albuterol (salbutamol) concentrations were found to be 2.5 times higher among patients who died of asthma compared with controls. It is speculated that such toxic concentrations could cause tachyarrhythmias under conditions of hypoxia and hypokalemia. The risk of asthma exacerbations and near-fatal attacks may also be increased among patients dispensed fenoterol, but this association may be largely due to confounding by severity. Although salmeterol does not appear to increase the risk of near-fatal attacks, there is a consistent association with the use of nebulized beta(2)-agonists. Nebulized and oral beta(2)-agonists are also associated with an increased risk of cardiovascular death, ischemic heart disease and cardiac failure. Caution should be exercised when first prescribing a beta-agonist for patients with cardiovascular disease. A potential mechanism for adverse effects with regular use of beta(2)-agonists is tachyphylaxis. Tachyphylaxis to the bronchodilator effects of long-acting beta(2)-agonists can occur, but has been consistently demonstrated only for formoterol (eformoterol) a full agonist, rather than salmeterol, a partial agonist. Tachyphylaxis to protection against induced bronchospasm occurs with both full and partial beta(2)-agonists, and probably within a matter of days at most. Underlying airway responsiveness to directly acting bronchoconstricting agents is not increased when the bronchodilator effect of the regular beta(2)-agonist has been allowed to wear off, although there may be an increase in responsiveness to indirectly acting agents. While there has been speculation that underlying airway inflammation in asthma may be made worse by regular use of short-acting beta(2)-agonists, in contradistinction, a number of studies have shown that long-acting beta(2)-agonists have positive anti-inflammatory effects. An Australian Cochrane Airways Group systematic review of the randomized, controlled trials of short-acting beta-agonists found only minimal and clinically unimportant differences between regular use and use as needed. Regular short-acting treatment was better than placebo. However, a subsequent systematic review has found that regular use of long-acting beta-agonists had significant advantages over regular use of short-acting beta-agonists. More studies and data are needed on the regular use of beta(2)-agonists in patients not taking inhaled corticosteroids, and in potentially vulnerable groups, such as the elderly and those with particular genotypes for the beta-receptor, who might be more prone to adverse effects.

Asthma deaths; persistent and preventable mortality

Bronchial asthma remains a significant cause of mortality at all ages, despite the increased understanding of its pathogenesis and the range of drugs available for its treatment. Changes in therapeutic management can influence death rates and constant surveillance, combined with high-quality post mortem investigations, is essential. Disease severity, poor disease management and adverse psychosocial circumstances are all risk factors for asthma mortality. Bronchial asthma causes characteristic histological changes in the mucosa of the airways which are present even before the clinical diagnosis of asthma can be made. These include fibrous thickening of the lamina reticularis of the epithelial basement membrane, smooth muscle hypertrophy and hyperplasia, increased mucosal vascularity and an eosinophil-rich inflammatory cell infiltrate. In addition, mucoid plugging of the airway lumen is frequently associated with fatal asthma. The recognition of these changes can allow the diagnosis of asthma to be made for the first time at autopsy, in those cases where asthma goes undiagnosed in life. Acute severe asthma may be accompanied by pneumothorax and surgical emphysema of the mediastinum. Disorders which may mimic asthma include pulmonary embolism, chronic obstructive pulmonary disease and anaphylaxis, but careful post mortem examination and appropriate investigations should reveal the true cause of death.

Cardiovascular side effects of inhaled salbutamol in hypoxic asthmatic patients

BACKGROUND

Beta-2 adrenoceptor agonists have been associated with sudden death in asthma patients but the cause and underlying mechanism are unclear. Animal experiments indicate that the combination of hypoxia and beta2 agonists may result in detrimental cardiovascular effects. A study was undertaken to investigate the effect of hypoxia on the systemic vascular effects of salbutamol in patients with asthma who are hypoxic by assessing forearm blood flow (FBF) as a measure of peripheral vasodilatation.

METHODS

Eight men with mild asthma underwent the following treatments: normoxia + placebo (NP), normoxia + salbutamol (NS), hypoxia + placebo (HP), and hypoxia + salbutamol (HS). The period of mask breathing started at t=0 minutes, lasted for 60 minutes, and at 30 minutes 800 microg salbutamol was inhaled. The experiment was completed 30 minutes after the inhalation (t=60 minutes). For the hypoxia treatment the SpO2 level was 82%. Differences between treatments were sought using factorial ANOVA on percentage change from the pretreatment value.

RESULTS

There were no significant differences in blood pressure and potassium levels between the treatments. After 60 minutes the increase in FBF was 13% (95% CI -12 to 39) more for HP treatment than for NP, 21% (95% CI -5 to 46) more for NS than for NP, and 32% (95% CI 7 to 58) more for HS than for HP (p=0.016). The inhalation of salbutamol during hypoxia resulted in a significant increase in FBF of 45% (95% CI 20 to 71) compared with NP (p=0.001).

CONCLUSION

Patients with asthma who are hypoxic and inhale beta2 agonists have serious systemic vascular side effects which may be an additional explanation for the association between asthma treatment and sudden death.

Cardiovascular side effects of inhaled salbutamol in hypoxic asthmatic patients

BACKGROUND

Beta-2 adrenoceptor agonists have been associated with sudden death in asthma patients but the cause and underlying mechanism are unclear. Animal experiments indicate that the combination of hypoxia and β2 agonists may result in detrimental cardiovascular effects. A study was undertaken to investigate the effect of hypoxia on the systemic vascular effects of salbutamol in patients with asthma who are hypoxic by assessing forearm blood flow (FBF) as a measure of peripheral vasodilatation.

METHODS

Eight men with mild asthma underwent the following treatments: normoxia + placebo (NP), normoxia + salbutamol (NS), hypoxia + placebo (HP), and hypoxia + salbutamol (HS). The period of mask breathing started at t=0 minutes, lasted for 60 minutes, and at 30 minutes 800 μg salbutamol was inhaled. The experiment was completed 30 minutes after the inhalation (t=60 minutes). For the hypoxia treatment the Spo2 level was 82%. Differences between treatments were sought using factorial ANOVA on percentage change from the pretreatment value.

RESULTS

There were no significant differences in blood pressure and potassium levels between the treatments. After 60 minutes the increase in FBF was 13% (95% CI –12 to 39) more for HP treatment than for NP, 21% (95% CI –5 to 46) more for NS than for NP, and 32% (95% CI 7 to 58) more for HS than for HP (p=0.016). The inhalation of salbutamol during hypoxia resulted in a significant increase in FBF of 45% (95% CI 20 to 71) compared with NP (p=0.001).

CONCLUSION

Patients with asthma who are hypoxic and inhale β2 agonists have serious systemic vascular side effects which may be an additional explanation for the association between asthma treatment and sudden death.

Prevalence of asthma among schoolchildren in Patras, Greece: three surveys over 20 years

BACKGROUND

The aim of the present study was to compare the prevalence of asthma among schoolchildren in 1978, 1991, and 1998 in Patras, Greece.

METHODS

The study populations of the three comparable cross sectional surveys comprised third and fourth grade public school children in Patras, Greece. Sample sizes in 1978, 1991, and 1998 were 3735, 2952 and 3397 children and response rates were 80.4%, 81.9%, and 90.6%, respectively. Prevalence of current, non-current, and lifetime asthma or recurrent wheezing was determined by parental questionnaire. Personal communication with the parents of asthmatic children in 1991 and 1998 provided data on lost schooldays.

RESULTS

Prevalence rates of current asthma or wheezing in 1978, 1991, and 1998 were 1.5%, 4.6%, and 6.0%, respectively (1978-91: p=0.01, 1991-98: p=0.02, 1978-98: p=0.03). Lifetime prevalences of asthma or wheezing in 1991 and 1998 were 8.0% and 9.6%, respectively (p=0.03). Current diagnosed asthma increased proportionally to diagnosed wheezing during 1991-98. The number of schooldays lost in the previous 2 years because of asthma did not change (p>0.1) between 1991 (0.31 per child) and 1998 (0.34 per child).

CONCLUSIONS

Our results support a true increase in the prevalence of current and lifetime asthma in the last 20 years among pre-adolescent children in Patras, Greece.

Are asthma medications and management related to deaths from asthma?

There is controversy about the role of beta-agonists in asthma mortality, and the impact of asthma management plans remains unclear. We compared blood beta-agonist levels in patients dying from asthma with those in controls, and estimated the risks associated with specific classes of medication and patterns of management. We identified 89 asthma deaths and recruited 322 patients presenting to hospitals with acute asthma. A questionnaire was administered to the next of kin in 51 cases, and to 202 controls. Blood drawn from 35 cases and 229 controls was assayed for salbutamol. Smoking, drinking, and family problems were significantly more likely among the cases of asthma death than among the controls. The two groups were reasonably well matched with regard to markers of chronic asthma severity. Cases of asthma death were significantly less likely than controls to use a peak flow meter. Written action plans were associated with a 70% reduction in the risk of death. Use of nebulized bronchodilators or oral steroids was significantly more likely in cases of asthma death. Mean blood salbutamol concentrations were 2.5 times higher in cases of asthma. The use of oral steroids for an attack of asthma reduced the risk of death by 90%. More widespread adoption of written asthma management plans, with less reliance on beta-agonists and closer medical supervision, should reduce asthma mortality.

Case-control study of salmeterol and near-fatal attacks of asthma

BACKGROUND

A case-control study was undertaken to investigate the hypothesis that the use of the long acting beta agonist salmeterol increases the risk of a near-fatal attack of asthma.

METHODS

The cases comprised admissions to the intensive care unit (ICU) for asthma in 14 major hospitals within the Wessex region in 1992. For each of the cases four age-matched controls were selected from asthma admissions to the same hospital during the same period. Information on prescribed drug therapy for the 48 cases and 185 controls was collected from the hospital admission records.

RESULTS

The patients admitted to the ICU had greater chronic asthma severity and had generally been prescribed more asthma drugs than the control admissions to hospital. The relative risk of a near-fatal attack of asthma in patients prescribed inhaled salmeterol was 2.32 (95% CI 1.05 to 5.16), p = 0.04. However, the salmeterol relative risk decreased to 1.42 (95% CI 0.49 to 4.10), p = 0.52 when the analysis was restricted to the more chronically severe patients (those in the subgroup of patients with a hospital admission for asthma in the previous 12 months). These findings suggest that the increased unadjusted relative risk with salmeterol is predominantly due to confounding by severity--that is, the increased relative risk is due to patients with more severe asthma (at greatest risk of a near-fatal asthma attack) being preferentially prescribed salmeterol. This interpretation is supported by the finding in this study that, within the control group (selected from the population of asthmatics requiring hospital admission), salmeterol was preferentially prescribed to the most severe patients (a threefold greater prescription of salmeterol to control patients if they had been admitted to hospital in the 12 months prior to the index admission). There was no increased risk of a near-fatal attack of asthma in patients prescribed a beta agonist by metered dose inhaler (OR 0.75 (95% CI 0.31 to 1.78), p = 0.51). In contrast, the relative risks for beta agonists delivered by nebulisation (OR 3.86 (95% CI 1.99 to 7.50), p < 0.001) and oral theophylline (OR 2.45 (95% CI 1.26 to 4.78), p < 0.01) were increased and did not markedly decrease when the analysis was restricted to the more severe asthmatic subjects.

CONCLUSIONS

Although these findings are not conclusive, particularly because of the small numbers involved in some subgroup analyses, they suggest that the use of salmeterol by patients with chronic severe asthma is not associated with a significantly increased risk of a near-fatal attack of asthma. If a near-fatal asthma attack is considered to be an intermediate step in a process by which a severe attack of asthma may become fatal, these results would suggest that salmeterol is unlikely to be associated with an increased risk of death, at least by this mechanism.

International trends in asthma mortality

Throughout the 20th century many different patterns of asthma mortality have been observed. Following relatively stable asthma mortality rates during the first half of this century, there has been a gradual increase in asthma mortality in many countries over the last 50 years. Although a number of possible explanations have been proposed to explain this trend-including increases in asthma prevalence, increases in exposure to factors that trigger asthma attacks and changes in asthma management-their relative contribution in different countries is uncertain. Another pattern is that of sudden marked increases in asthma mortality occurring in at least seven countries in the 1960s and in New Zealand in the 1970s. Available evidence indicates that the cause of these 'epidemics' was the use of high dose preparations of two specific beta-agonist drugs, namely isoprenaline forte and fenoterol. The most recent trend observed in a number of western countries during the last decade has been a gradual reduction in asthma mortality; this may relate to improvements in the management of asthma.

Risk of severe life threatening asthma and beta agonist type: an example of confounding by severity

BACKGROUND

A study was undertaken to test the hypothesis that a particular inhaled beta agonist, fenoterol, increases the incidence of severe life threatening asthma.

METHODS

A retrospective cohort was assembled comprising 655 patients with asthma aged 15-55 years who attended a single Auckland hospital for acute asthma between 1 January 1986 and 31 December 1987 (the "index event"). Patients were followed for the occurrence of death from asthma or admission to the intensive care unit for asthma, until death or 31 May 1989. Data on asthma medications and asthma severity were obtained from forms used specifically for managing patients with acute asthma in the emergency department and maintained as part of the hospital record and/or from the hospital record (when patients were admitted).

RESULTS

Following the index event 90 admissions to the intensive care unit (ICU) and 15 asthma deaths were identified. Before adjusting for asthma severity, patients using inhaled fenoterol had a greater incidence of severe life threatening asthma than patients using inhaled salbutamol (RR = 2.1, 95% CI 1.4 to 3.1). After controlling for two markers of severe asthma used in previous studies-a hospital admission in the previous year and prescribed oral corticosteroids-the relative risk estimate declined to 1.5 (95% CI 1.0 to 2.3). After controlling further for the number of hospital admissions during the study period, continuous oral corticosteroid use rather than short courses of treatment, severity of the previous attack requiring a hospital visit, and race, fenoterol was not associated with severe life threatening asthma at the time of attendance for a previous hospital visit (RR = 1.0, 95% CI 0.6 to 1.7).

CONCLUSION

Fenoterol is used more often by patients with severe asthma and, after adjusting for differences in baseline risk, it does not increase the risk of severe life threatening asthma.

Oral vs inhaled asthma therapy. Pros, cons and combinations

A number of oral and inhaled drugs are available for the long term management of patients with persistent asthma, yet the disease continues to be associated with significant morbidity and mortality. Over the past years, inhaled glucocorticoids have become established as a cornerstone of maintenance therapy because of their demonstrated clinical efficacy, ability to reduce bronchial inflammation and good tolerability. Other inhaled drugs (e.g. sodium cromoglycate, nedocromil, long-acting beta 2 agonists) also play a role in the long term treatment of patients with asthma. However, many patients (especially children and the elderly) find inhalers difficult to use, and poor inhalation technique can affect the amount of drug reaching the lungs and response to therapy. Oral drug administration is simple, but, until recently, oral asthma therapy has primarily consisted of sustained-release theophylline and glucocorticoids. Theophylline has a narrow therapeutic index, necessitating regular monitoring of serum drug concentrations, and long term oral glucocorticoid therapy is associated with potentially serious adverse events including osteoporosis with bone fracture. The recent development of orally administered leukotriene receptor antagonists (e.g. zafirlukast) and 5-lipoxygenase inhibitors (e.g. zileuton) offers novel mechanisms of action and potential solutions to compliance issues associated with regular administration of inhaled asthma therapy. These drugs have demonstrated efficacy as maintenance therapy in patients with asthma and, importantly, lack the adverse effects associated with long term systemic glucocorticoid therapy. Further clinical trials and the increasing use of these new therapies will help to establish the precise role of orally administered leukotriene receptor antagonists and 5-lipoxygenase inhibitors in the long term management of patients with asthma.