Paradoxical bronchoconstriction with albuterol administered by metered-dose inhaler and nebulizer solution

2023 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations: Summary From the Basic Life Support; Advanced Life Support; Pediatric Life Support; Neonatal Life Support; Education, Implementation, and Teams; and First Aid Task Forces

The International Liaison Committee on Resuscitation engages in a continuous review of new, peer-reviewed, published cardiopulmonary resuscitation and first aid science. Draft Consensus on Science With Treatment Recommendations are posted online throughout the year, and this annual summary provides more concise versions of the final Consensus on Science With Treatment Recommendations from all task forces for the year. Topics addressed by systematic reviews this year include resuscitation of cardiac arrest from drowning, extracorporeal cardiopulmonary resuscitation for adults and children, calcium during cardiac arrest, double sequential defibrillation, neuroprognostication after cardiac arrest for adults and children, maintaining normal temperature after preterm birth, heart rate monitoring methods for diagnostics in neonates, detection of exhaled carbon dioxide in neonates, family presence during resuscitation of adults, and a stepwise approach to resuscitation skills training. Members from 6 International Liaison Committee on Resuscitation task forces have assessed, discussed, and debated the quality of the evidence, using Grading of Recommendations Assessment, Development, and Evaluation criteria, and their statements include consensus treatment recommendations. Insights into the deliberations of the task forces are provided in the Justification and Evidence-to-Decision Framework Highlights sections. In addition, the task forces list priority knowledge gaps for further research. Additional topics are addressed with scoping reviews and evidence updates.

2023 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations: Summary From the Basic Life Support; Advanced Life Support; Pediatric Life Support; Neonatal Life Support; Education, Implementation, and Teams; and First Aid Task Forces

The International Liaison Committee on Resuscitation engages in a continuous review of new, peer-reviewed, published cardiopulmonary resuscitation and first aid science. Draft Consensus on Science With Treatment Recommendations are posted online throughout the year, and this annual summary provides more concise versions of the final Consensus on Science With Treatment Recommendations from all task forces for the year. Topics addressed by systematic reviews this year include resuscitation of cardiac arrest from drowning, extracorporeal cardiopulmonary resuscitation for adults and children, calcium during cardiac arrest, double sequential defibrillation, neuroprognostication after cardiac arrest for adults and children, maintaining normal temperature after preterm birth, heart rate monitoring methods for diagnostics in neonates, detection of exhaled carbon dioxide in neonates, family presence during resuscitation of adults, and a stepwise approach to resuscitation skills training. Members from 6 International Liaison Committee on Resuscitation task forces have assessed, discussed, and debated the quality of the evidence, using Grading of Recommendations Assessment, Development, and Evaluation criteria, and their statements include consensus treatment recommendations. Insights into the deliberations of the task forces are provided in the Justification and Evidence-to-Decision Framework Highlights sections. In addition, the task forces list priority knowledge gaps for further research. Additional topics are addressed with scoping reviews and evidence updates.

Extracellular metabolism of 3',5'-cyclic AMP as a source of interstitial adenosine in the rat airways

In the respiratory tract, intracellular 3',5'-cAMP mediates smooth muscle relaxation triggered by the β₂-adrenoceptor/Gs protein/adenylyl cyclase axis. More recently, we have shown that β₂-adrenoceptor agonists also increase extracellular 3',5'-cAMP levels in isolated rat trachea, which leads to contraction of airway smooth muscle. In many other tissues, extracellular 3',5'-cAMP is metabolized by ectoenzymes to extracellular adenosine, a catabolic pathway that has never been addressed in airways. In order to evaluate the possible extracellular degradation of 3',5'-cAMP into 5'-AMP and adenosine in the airways, isolated rat tracheas were incubated with exogenous 3',5'-cAMP and the amount of 5'-AMP, adenosine and inosine (adenosine metabolite) produced was evaluated using ultraperformance liquid chromatography-tandem mass spectrometry. Incubation of tracheal tissue with 3',5'-cAMP induced a time- and concentration-dependent increase in 5'-AMP, adenosine and inosine in the medium. Importantly, IBMX (non-selective phosphodiesterase (PDE) inhibitor) and DPSPX (selective ecto-PDE inhibitor) reduced the extracellular conversion of 3',5'-cAMP to 5'-AMP. In addition, incubation of 3',5'-cAMP in the presence of AMPCP (inhibitor of ecto-5'-nucleotidase) increased extracellular levels of 5'-AMP while drastically reducing extracellular levels of adenosine and inosine. These results indicate that airways express an extracellular enzymatic system (ecto-phosphodiesterase, ecto-5'-nucleotidase and adenosine deaminase) that sequentially converts 3',5'-cAMP into 5'-AMP, adenosine and inosine. The observation that extracellular 3',5'-cAMP is a source of interstitial adenosine supports the idea that the extrusion and extracellular metabolism of 3',5'-cAMP has a role in respiratory physiology and pathophysiology.

Paradoxical bronchospasm: a rare adverse effect of fenoterol use

Paradoxical bronchospasm refers to the constriction of the airways after treatment with a sympathomimetic bronchodilator. Theoretically, bronchodilators, such as beta-agonist inhalers, act to ease asthma symptoms by relaxing the muscles surrounding the walls of the bronchial tubes, which relieve bronchial constriction. However, in rare instances, some patients develop respiratory distress or even respiratory failure after inhaled bronchodilator use, although the exact mechanism for this adverse effect is unknown. We report a male, with a known asthma history diagnosed for more than one decade, receiving fenoterol (Berotec®) for wheezing control and the worsening of his clinical condition immediately after bronchodilator administration.

The paradoxical response to short-acting bronchodilator administration in patients with chronic obstructive pulmonary disease

Background

There are a few studies about paradoxical bronchodilator response (BDR), which means a decrease in forced expiratory volume in 1 second (FEV₁) or forced vital capacity (FVC) after short-acting bronchodilator administration in patients with chronic obstructive pulmonary disease (COPD). We evaluated the effect of paradoxical BDR on the clinical outcomes of COPD patients in South Korea.

Methods

We analyzed the KOrea COpd Subgroup Study team (KOCOSS) cohort data in South Korea between January 2012 and December 2017. BDR was defined as at least a 12% and 200-mL reduction in FEV₁ or FVC after bronchodilator administration.

Results

A total of 1,991 patients were included in this study. A paradoxical BDR was noted in 57 (2.9%) patients and was independently associated with worse dyspnea and poor quality of life. High C-reactive protein (CRP) levels were associated with a paradoxical BDR (OR, 1.05; 95% CI, 1.01-1.09; P=0.003). However, paradoxical BDR was not associated with severe acute exacerbations. Pre-bronchodilator FEV₁ (L) showed a higher area under the curve (AUC) for predicting severe acute exacerbations than the post-bronchodilator FEV₁ (L) in the paradoxical BDR group (0.788 vs. 0.752).

Conclusion

A paradoxical reduction of FEV₁ or FVC after bronchodilator administration may be associated with chronic inflammation in the airway and independently associated with worse respiratory symptoms and poor quality of life.

Paradoxical bronchoconstriction caused by β2-adrenoceptor agonists

Introduction

Salbutamol and terbutaline are short-acting β₂ adrenergic agonists that produce bronchial smooth muscle relaxation and are widely used in obstructive pulmonary diseases. Nevertheless, their use has been the cause of a paradoxical bronchoconstriction, which is a rare and potentially serious adverse reaction. The aim of this study is to report a case of paradoxical bronchoconstriction caused by β₂ adrenergic agonists.

Methods

This case is about a 50-year-old asthmatic patient who describes a history of repeated acute asthma attacks after salbutamol inhalation or terbutaline nebulization. A double-blind crossover study was performed over 3 days, in order to compare the effects of each bronchodilator. Forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), and maximal expiratory flow 25-75 (MEF25-75) were measured.

Results

On the first day, a bronchoconstriction caused by deep and repeated inhalations was eliminated. On the second day, an airway obstruction was confirmed by a decrease in FEV₁ at 40% from baseline values after nebulization of a standard dose of terbutaline. On the third day, a spirometry was performed before and after nebulization of a standard dose of ipratropium bromide, and there were no significant changes in the spirometric parameters. Finally the patient was discharged with a written warning mentioning the danger of salbutamol and terbutaline use.

Conclusion

Salbutamol and terbutaline are generally well-tolerated β₂ adrenergic agonists. Nevertheless, in rare cases, these substances can cause a paradoxical bronchoconstriction. Doctors must therefore remain vigilant about its side effect and possibly investigate each case.

Methodological evaluation of human research on asthmagenicity and occupational cleaning: a case study of quaternary ammonium compounds ("quats")

In this paper, we review methodological approaches used in studies that evaluated the association between occupational exposure to quaternary ammonium compounds (quats) and occupational asthma. This association is of interest because quats are a common active ingredient of disinfectants and have been linked to work-related asthma in some circumstances. However, any evidence-based assessment of an exposure-outcome association needs to consider both strengths and limitations of the literature. We focus on publications cited by various US and international organizations. Eighteen investigations included in the review fall into two broad categories: case reports and challenge studies of individual patients and population studies that examined the association between quats and asthma occurrence in groups of subjects. We evaluated these studies guided by questions that address whether: exposure data on specific quat(s) and other agents that may cause asthma were included, new asthma cases were differentiated from asthma exacerbation, and information on respiratory sensitivity versus irritation was given. We also assessed consistency across studies. Studies of individual patients, particularly those that provided detailed information on challenge test results, document cases of asthma induced by exposure to quats. By contrast, studies of occupational groups with the highest potential for quats exposure (e.g., cleaners and farmers) do not consistently report increased incidence of asthma due specifically to quats. The unresolved methodological issues include: poor understanding of exposure pathways considering that quats are non-volatile, lack of quantitative data allowing for identification of an asthmagenicity threshold, insufficient information on whether quats are sensitizers or act via dose-dependent irritation or some other mechanism, and inability to quantify risk of new-onset asthma attributable to quats. Another important area of uncertainty is the lack of information on the specific quats being used. There is also a lack of data capable of distinguishing the effects of quats from those of other chemical and biological workplace exposures. The current state-of-the-science does not allow a proper assessment of the potential link between quats and occupational asthma.

Determining the optimal time to assess the reversibility of airway obstruction

Context:

The optimal time to interpret bronchodilator reversibility remains controversial. This time may affect a positive diagnosis and manage asthma and chronic obstructive pulmonary disease (COPD).

Aims:

We sought to document the time when maximum respiratory function is reached after inhalation of salbutamol and to define the optimal time of bronchodilator response to assess the reversibility or non reversibility of airway obstruction.

Subjects and Methods:

This prospective analytical study was spread over 8 months and included 58 patients with asthma or COPD with airway obstruction. Spirometry was performed before and at 5, 10, 15, 20, and 30 min after salbutamol inhalation (200 mcg) administered through pressurized metered-dose inhalers and large volume spacer.

Results:

After salbutamol inhalation, the mean individual peak bronchodilation occurred at 20 min for the forced vital capacity and at 30 min for the forced expiratory volume in 1 s. The percentage of reversible patients in our sample was guideline dependent. It increased from 53% to 67.2% when using the American Thoracic Society/European Respiratory Society definition compared to using the Global Initiative for Chronic Obstructive Lung Disease. The maximum number of reversible patients was significantly different at 20 min compared to 5 and 10 min.

Conclusions:

Interpreting bronchodilator reversibility after 20 min was the ideal time to judge the reversibility or nonreversibility in obstructive ventilatory disorders in adults.

Safety and effectiveness of albuterol solutions with and without benzalkonium chloride when administered by continuous nebulization

PURPOSE

The results of a study to determine if rates of poor response differ in patients receiving continuous nebulized albuterol (CNA) therapy with or without the preservative benzalkonium chloride are presented.

METHODS

A retrospective analysis of the records of all patients who received CNA therapy at a large academic medical center from July 2015 to January 2016 was conducted. Data from patient evaluations performed before and after a change to benzalkonium chloride-containing albuterol were collected. The primary outcome was the rate of poor patient response, defined as a composite endpoint. Secondary outcomes included duration of therapy, dosing requirements, and duration of supplemental oxygen therapy.

RESULTS

There was no significant difference in rates of poor response between patients exposed (n = 80) and patients not exposed (n = 48) to benzalkonium chloride (16% and 17%, respectively; p = 0.95). The cohort not exposed to benzalkonium chloride had a median CNA duration of 7.0 hours, as compared with 10.5 hours for the cohort exposed to benzalkonium chloride, but this difference was not significant (p = 0.19). There were no significant differences between the benzalkonium chloride-exposed and nonexposed cohorts in the maximum dosing requirement (12.6 mg/hr versus 12.8 mg/hr, p = 0.89) or median duration of supplemental oxygen use (27.5 hours versus 16.5 hours, p = 0.77).

CONCLUSION

A study of hospitalized patients receiving CNA detected no significant difference in the frequency of poor response to therapy between groups receiving benzalkonium chloride-free versus benzalkonium chloride-containing albuterol products.

Prevalence of paradoxical bronchoconstriction after inhaled albuterol

PURPOSE

Paradoxical bronchoconstriction with resulting decreased airflow occurs in some patients after administration of bronchodilators. This study assessed the frequency of paradoxical bronchoconstriction in a real-life clinical setting at a large academic medical center.

PROCEDURES

We analyzed data from 4593 patients who underwent pre- and post-bronchodilator spirometry testing. We assessed the forced expiratory volume in the first second (FEV₁) and forced vital capacity (FVC) before and after the administration of an inhaled short-acting β₂-agonist. Patients were categorized into 3 groups: bronchodilation, no significant change and paradoxical bronchoconstriction.

MAIN FINDINGS

When assessing response to bronchodilators, 201 (4.4%) patients demonstrated significant bronchoconstriction, whereas 849 (18.5%) showed bronchodilation. The majority (3543 or 77.1%) had no significant change. There were no significant relationships noted between paradoxical bronchoconstriction and sex, race/ethnicity or body mass index.

CONCLUSIONS

A significant subset of patients experience paradoxical bronchoconstriction after albuterol administration. Further research to better understand the clinical implications of paradoxical acute bronchoconstriction is needed.

Near Fatal Asthma in an Inner City Population

Near-fatal asthma (NFA) is highly prevalent in inner city population. Patients who present with NFA require timely intervention, which necessitates knowledge of appropriate associated risk factors. The purpose of the study was to look and identify the salient features of an asthma exacerbation that are more likely to be associated with NFA in inner city population. We conducted a retrospective analysis of patients who were discharged from the hospital with a diagnosis of acute asthma exacerbation. Two hundred eighteen patients were included in the study. Patients who required intubation during the course of their hospitalization were defined as NFA and the rest were defined as non-near-fatal asthma (NNFA). Multiple patient parameters were compared between the 2 groups; 60 patients met the definition of NFA. There was no difference between NFA and NNFA groups with respect to sex, race, and history of smoking and asthma treatment modalities before presentation. NFA was seen more commonly in heroin (40% vs. 25.9%; P < 0.05) and cocaine users (28.3% vs. 16.5%; P < 0.05). A history of exacerbation requiring intensive care unit (ICU) care was more common among the NFA patients (55% vs. 40.5%; P = 0.05). A history of intubation for an exacerbation was more commonly seen in patients presenting with NFA (51.7% vs. 35.4%; P < 0.05). The NNFA group was more likely to have a primary care physician and to be discharged home (65.6% vs. 51.7%, P < 0.05; and 71.7 vs. 79.1%, P < 0.05). In a multi-logistic regression model, including age, sex, race, heroin and cocaine use, history of intubation and ICU admission, medications, use of noninvasive ventilation, primary care physician, and pH <7.35, PCO2 >45 mm Hg, and FiO2 >40% on initial blood gas, NFA was predicted only by PaCO2 >45 [odds ratio (OR = 6.7; P < 0.001)] and FiO2 >40% (OR = 3.5; P = 0.002). Use of noninvasive ventilation was a negative predictor of NFA (OR = 0.2; P < 0.001). Asthmatic patients who carry a history of intubation with mechanical ventilation for an asthma exacerbation, admissions to the ICU, or those who indulge in recreational drugs like cocaine or heroin should be closely monitored for clinical deterioration.

The effects of daily bathing on symptoms of patients with bronchial asthma

Background

The influence of bathing in asthma patients is not yet fully known.

Objective

We conducted an observational study to investigate changes in symptoms and their degree by bathing in asthmatic patients.

Methods

A questionnaire focusing on ever experienced bathing-induced symptom changes and their degree, as well as contributing factors, was designed and administered to asthmatic patients in the outpatient department of our institute between January 2012 and November 2013.

Results

Two hundred fifteen cases were recruited. In 60 cases (27.9%), asthmatic symptoms appeared, including 20 cases of chest discomfort (33.3%), 19 cases of cough (31.7%), and 21 cases of wheezing (35.0%). The triggering factors included vapor inhalation (32 cases, 53.3%), hydrostatic pressure on the thorax due to body immersion in the bathtub (26 cases, 43.3%), and sudden change of air temperature (16 cases, 26.7%). Thirty-eight cases (17.7%) experienced improvement in active asthmatic symptoms by bathing. Vapor inhalation was the most common contributing factor (34 cases, 89.5%), followed by warming of the whole body (13 cases, 34.2%). There was no relationship between asthma severity and the appearance of bathing-induced symptoms or improvement of active asthmatic symptoms by bathing.

Conclusion

The effects of bathing in asthmatic patients widely differed from patient to patient and their etiology includes several factors. For those who suffer from bathing-induced asthma symptoms, preventive methods, such as premedication with bronchodilators before bathing, should be established. This study is registered in the University Hospital Medical Information Network (UMIN) clinical trials registry in Japan with the registration number UMIN000015641.

Radiological correlates and clinical implications of the paradoxical lung function response to β₂ agonists: an observational study

BACKGROUND

Bronchodilator response has been noted in a significant proportion of patients with chronic obstructive pulmonary disease (COPD). However, there are also reports of a paradoxical response to β₂ agonists resulting in bronchoconstriction. Asymptomatic bronchoconstriction is likely to be far more common than is symptomatic bronchoconstriction with β₂ agonists, but no systematic studies have been done. We assessed the prevalence of paradoxical response in current and former smokers with and without COPD, and its radiological correlates and clinical implications.

METHODS

Non-Hispanic white and African-American patients (aged 45-80 years) from a large multicentre study COPDGene were classified into two groups on the basis of a paradoxical response, defined as at least a 12% and 200 mL reduction in forced expiratory volume in 1 sec (FEV₁) or forced vital capacity (FVC), or both, after administration of a shortacting β₂ agonist (180 μg salbutamol).

FINDINGS

Patients were recruited from January, 2008, to June, 2011. 9986 (96%) of 10,364 patients enrolled in the COPDGene study were included in the analysis population (mean age 59·6 years [SD 9·0]). Paradoxical response was noted in 453 (5%) of 9986 patients and the frequency was similar in patients with COPD (198 [4%] of 4439) and smokers without airflow obstruction (255 [5%] of 5547). Compared with white patients, a paradoxical response was twice as common in African-American patients (227 [7%] of 3282 vs 226 [3%] of 6704; p<0·0001). In the multivariate analyses, African-American ethnic origin (adjusted odds ratio 1·89, 95% CI 1·50-2·39; p<0·0001), less emphysema (0·96, 0·92-0·99; p=0·023), and increased wall-area percentage of the segmental airways (1·04, 1·01-1·08; p=0·023) were independently associated with a paradoxical response. A paradoxical response was independently associated with worse dyspnoea (adjusted β for Modified Medical Research Council Dyspnoea Scale 0·12 [95% CI 0·00 to 0·24]; p=0·05), lower 6 min walk distance (-45·8 [-78·5 to -13·2]; p=0·006), higher Body Mass Index, Airflow Obstruction, Dyspnea, and Exercise Capacity (BODE) index (0·31 [0·19 to 0·43]; p<0·0001), and a greater frequency of severe exacerbations (increased by a factor of 1·35, 1·00-1·81; p=0·048).

INTERPRETATION

Paradoxical response to β₂ agonists is associated with respiratory morbidity and is more common in African-Americans. These findings might have implications for the use of β2agonists in some patients.

FUNDING

National Institutes of Health.

Safety of Levalbuterol Compared to Albuterol in Patients With a Tachyarrhythmia

Objective: To determine the safety of levalbuterol versus albuterol in patients with a tachyarrhythmia. Data Sources: A PubMed search was conducted using the MeSH search terms levalbuterol, albuterol, and tachyarrhythmia. Bibliographies of relevant articles were reviewed for additional citations. Study Selection and Data Extraction: Search results were limited to humans and randomized controlled trials. Those studies that excluded patients with predetermined tachyarrhythmias were excluded from this review. Trials that failed to compare levalbuterol and albuterol outcomes were excluded. Data Synthesis: Beta-2 receptor agonists are the mainstay of treatment in patients with respiratory disease, such as asthma or chronic obstructive pulmonary disease. Racemic albuterol has been linked to poor outcomes due to the fact that it contains both the S-isomer and the R-isomer. Levalbuterol, the “pure” R-isomer, has been thought to decrease cardiac side effects since it only contains the therapeutic component of the racemic mixture. Patients with tachyarrhythmias are at an increased probability to experience harmful, if not fatal, cardiac side effects from these drugs. Limitations of current studies include a lack of data in patient populations with baseline tachyarrhythmias. Conclusions: Tachyarrhythmias put a patient at increased risk of poor outcomes, including death. Evidence for using either racemic albuterol or levalbuterol for respiratory disease management in these patients is lacking and insufficient. Randomized controlled trials show that in intensive care unit patient populations there is no clear advantage to using levalbuterol over albuterol; however, this did not hold true in pediatric populations. No clinical trials exist that look at a direct comparison of these 2 agents in patients with underlying tachyarrhythmias. Further research into the most efficacious and safe β-2 receptor agonists in this specialized patient population should be conducted to help reduce potential harmful outcomes.

Potential adverse effects of bronchodilators in the treatment of airways obstruction in older people: recommendations for prescribing

Asthma and chronic obstructive pulmonary disease (COPD) are common disorders that are associated with increasing morbidity and mortality in older people. Bronchodilators are used widely in patients with these conditions, but even when used in inhaled form can have systemic as well as local effects. Older people experience more adverse drug effects because of pharmacodynamic and pharmacokinetic changes and particularly drug-drug and drug-disease interactions. Cardiovascular disease is common in older people and beta-adrenoceptor agonists (beta-agonists) have inotropic and chronotropic effects that can increase arrhythmias and cardiomyopathy. They can also worsen or induce myocardial ischaemia and cause electrolyte disturbances that contribute to arrhythmias. Tremor is a well known distressing adverse effect of beta-agonist administration. Long-term beta-agonist use can be associated with tolerance, poor disease control, sudden life-threatening exacerbations and asthma-related deaths. Functional beta2-adrenoceptors are present in osteoblasts, and chronic use of beta-agonists has been implicated in osteoporosis. Inhaled anticholinergics are usually well tolerated but may cause dry mouth, which can be troublesome in older people. Pupillary dilatation, blurred vision and acute glaucoma can occur from escape of droplets from loosely fitting nebulizer masks. Although ECG changes have not been seen in randomized controlled trials of long-acting inhaled anticholinergics, supraventricular tachycardias have been observed in a 5-year randomized controlled trial of ipratropium bromide. Paradoxical bronchoconstriction can occur with inhaled anticholinergics as well as with beta-agonists, but tolerance has not been reported with anticholinergics. Anticholinergic drugs also cause central effects, most notably impairment of cognitive function, and these effects have been noted with inhaled agents. Use of theophylline is limited by its adverse effects, which range from commonly occurring gastrointestinal symptoms to palpitations, arrhythmias and reports of myocardial infarction. Seizures have been reported, but are rare. Theophylline is metabolized primarily by the liver, and commonly interacts with other medications. Its concentration in plasma should be monitored closely, especially in older people. Although many clinical trials have been conducted on bronchodilators in obstructive airways disease, the results of these clinical trials need to be interpreted with caution as older people are often under-represented and subjects with co-morbidities actively excluded from these trials.

Population pharmacodynamic model of bronchodilator response to inhaled albuterol in children and adults with asthma

BACKGROUND

Because interpatient variability in bronchodilation from inhaled albuterol is large and clinically important, we characterized the albuterol dose/response relationship by pharmacodynamic modeling and quantified variability.

METHODS

Eighty-one patients with asthma (24% African American [AA]; 8 to 65 years old; baseline FEV1, 40 to 80% of predicted) received 180 microg of albuterol from a metered-dose inhaler (MDI), and then 90 microg every 15 min until maximum improvement or 540 microg was administered; all then received 2.5 mg of nebulized albuterol. FEV1 was measured 15 min after each dose. The population cumulative dose/response data were fitted with a sigmoid maximum effect of albuterol (Emax) [maximum percentage of predicted FEV1 effect] model by nonlinear mixed-effects modeling. The influence of covariates on maximum percentage of predicted FEV1 reached after albuterol administration (Rmax) and cumulative dose of albuterol required to bring about 50% of maximum effect of albuterol (ED50) and differences between AA and white patients were explored.

RESULTS

ED50 was 141 microg, and Emax was 24.0%. Coefficients of variation for ED50 and Emax were 40% and 56%, respectively. Ethnicity was a statistically significant covariate (p < 0.05). AA and white patients reached 82.4% and 91.9% of predicted FEV1, respectively (p = 0.0004); and absolute improvement in percentage of predicted FEV1 was 16.6% in AA patients vs 26.7% in white patients (p < 0.0003). There were no baseline characteristic differences between AA and white patients. Nebulized albuterol increased FEV1 > or = 200 mL in 21% of participants. Heart rate and BP were unchanged from baseline after maximal albuterol doses.

CONCLUSIONS

Our model predicts that 180 microg of albuterol by MDI produces a 14.4% increase in percentage of predicted FEV1 over baseline (11.7% in AA patients, and 17.5% in white patients). Emax varies widely between asthmatic patients. AA patients are less responsive to maximal doses of inhaled albuterol than white patients.

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