Mast-cell stabilising agents to prevent exercise-induced bronchoconstriction.
BACKGROUND
Exercise-induced bronchoconstriction (or asthma) following strenuous physical exertion is common and can cause sub-optimal performance, symptoms such as cough, dyspnea, wheeze, chest tightness, and can lead people to avoid physical activity. Management focuses on prevention with pre-exercise treatment using various pharmacologic agents. Mast cell stabilizing agents are effective in attenuating exercise-induced bronchoconstriction but their effectiveness compared to bronchodilator agents is unclear.


OBJECTIVE
To quantitatively compare the effects of inhaling a single dose of either mast cell stabiliser - nedocromil sodium or sodium cromoglycate - to a single dose of short acting beta-agonists or anti-cholinergic agents - atropine or ipratropium bromide - prior to a strenuous exercise challenge in participants with asthma who are at least 6 years of age and suffer from reproducible exercise-induced bronchoconstriction. The review also compares the effects between a short acting beta-agonist alone to a combination of a short acting beta-agonist + mast cell stabiliser.


METHODS
We searched the Cochrane Airways Group ASTHMA and WHEEZ* trials register, Cochrane CENTRAL, Current Contents, review articles, textbooks and reference lists of articles. We also contacted the drug manufacturer and primary authors for additional citations.


METHODS
Randomised trials comparing a single prophylactic dose of a mast cell stabiliser to a short acting beta-agonist, anti-cholinergic agent, or a short acting beta-agonist alone to a combination of short acting beta-agonist plus a mast cell stabiliser to prevent exercise-induced bronchoconstriction in asthmatics over six years old. The exercise challenge had to conform to acceptable standards and pulmonary function (PFT) reported as percent decrease from baseline of FEV1 or peak flow. Complete protection (maximum % fall PFT <15% post-exercise) and clinical protection (50% improvement over placebo effect) measures were included.


METHODS
Trial inclusion and quality assessments were conducted independently by two reviewers using standardised forms. A second reviewer confirmed data extraction and calculations. Attempts were made to contact study authors. The pooled estimate involving continuous pulmonary function measures are reported as a weighted mean difference (WMD), dichotomous data as an odds ratio (OR), both with 95% confidence intervals (95%CI) using a random effects model. Heterogeneity tests for pooled results were performed.


RESULTS
Twenty-four trials (518 participants) conducted in 13 countries between 1976 and 1998 were included. All drugs were effective at attenuating the exercise-induced bronchoconstriction response but to varying degrees even within the same individual. Compared to anti-cholinergic agents, mast cell stabilisers were somewhat more effective at attenuating bronchoconstriction. On average the maximum fall on MCS was reduced to 7.1% compared to 13.8% on AC ( WMD = 6.7%; 95% CI: 3.3 to 10.0), provided more individuals with complete protection (73% vs 56%; OR = 2.2; 95% CI: 1.3 to 3.7) and clinical protection (73% vs 52%; OR = 2.7; 95% CI: 1.1 to 6.4). There were no subgroup differences based on age, severity, or study quality, and no adverse effects were reported for either agent group. When compared to short acting beta-agonists mast cell stabilisers were not as effective at preventing deterioration. On average the maximum fall on MCS was 11.2% compared to 4.3% on beta agonists ( WMD = 6.8%; 95% CI: 4.5 to 9.2). MCS provided fewer individuals with complete protection (66% vs 85%; OR = 0.3; 95% CI: 0.2 to 0.5) or clinical protection (55% vs 77%; OR = 0.4; 95% CI: 0.2 to 0.8). There were no significant subgroup differences based on age, severity, drug, delivery, or study quality. A non-significant difference in side effects was demonstrated with 11% of short acting beta-agonist patients experiencing side effects compared to 3% of those receiving mast cell stabilisers (OR = 0.2; 95% CI: 0.0 to 8.2). Combining masta-agonist patients experiencing side effects compared to 3% of those receiving mast cell stabilisers (OR = 0.2; 95% CI: 0.0 to 8.2). Combining mast cell stabilisers with a short acting beta-agonist did not produce significant advantages to pulmonary function over short acting beta-agonists alone. On average the maximum fall on SABA only was reduced to 5.3% compared to 3.5% on the combination ( WMD = 1.8%; 95% CI: -1.1 to 4.6). Beta-agonists alone provided fewer individuals with complete protection (68% vs 80%; OR = 0.5; 95% CI: 0.2 to 1.4) or clinical protection (70% vs 86%; OR=0.4; 95% CI: 0.1 to 1.2) but the difference did not reach significance (p=0.17). There were no subgroup differences.


CONCLUSIONS
In a population of stable asthmatics short acting beta-agonists, mast cell stabilisers, or anticholinergics will provide a significant protective effect against exercise-induced bronchoconstriction with few adverse effects. On average, SABAs resulted in more effective attenuation than mast cell stabilisers, while mast cell stabilisers were more effective than anti-cholinergic agents. Combining SABA and mast cell stabilisers may be appropriate in selected cases. The variability in the individual degree of response to these drugs in multi arm trials suggests clinicians and patients work together to identify the most effective prophylactic therapy.
Spooner
C H
CH
Division of Emergency Medicine, University of Alberta, 1G1.50 Walter Mackenzie Health Centre, 8440 - 112 ST, Edmonton, Alberta, Canada, T6G 2B7.
Spooner
G R
GR
Rowe
B H
BH
D000318:Adrenergic beta-Agonists / Q000627:therapeutic use*; D000328:Adult; D001250:Asthma, Exercise-Induced / Q000517:prevention & control*; D016084:Bronchoconstriction / Q000187:drug effects*; D002648:Child; D018680:Cholinergic Antagonists / Q000627:therapeutic use*; D006801:Humans; D008407:Mast Cells / Q000187:drug effects* / Q000502:physiology; D016032:Randomized Controlled Trials as Topic
D000318:Adrenergic beta-Agonists; D018680:Cholinergic Antagonists