Background: Nedocromil sodium and sodium cromoglycate inhaled shortly before exercise appear to reduce the severity of exercise-induced bronchoconstriction. There is some debate over which drug may be more effective.
Objectives: The objective of this review was to compare the effects on post-exercise lung function between prophylactic doses of nedocromil sodium (NSG) and sodium cromoglycate (SCG) in persons diagnosed with exercise-induced bronchoconstriction.
Search strategy: Randomized controlled trials were identified from the Cochrane Airways Review Group Asthma Register which compiles searches of CINAHL, EMBASE, MEDLINE and CENTRAL, plus hand searches for trials in 20 journals. Bibliographies of relevant studies and review articles were searched and primary authors, content experts and manufacturers of drugs were contacted for additional relevant studies. No language restrictions were applied.
Selection criteria: Randomized controlled trials comparing NCS to SCG in prophylactic treatment of exercise-induced bronchoconstriction were eligible. Studies were included if: the participants, aged 6 or over, had a confirmed diagnosis of asthma with exercise-induced bronchoconstriction, were subjected to an exercise challenge sufficient to trigger bronchoconstriction, and the measures of lung function were reported as either changes in forced expiratory volume in one second or peak expiratory flow rate.
Data collection and analysis: Data extraction and methodological quality assessments were conducted independently by two reviewers using standard forms and validated assessment criteria. In some cases results were extrapolated from graphs. Results from similar studies were pooled and reported as the weighted mean difference (WMD) or odds ratio (OR) with 95% confidence intervals (CI) using the random effects model.
Main results: Of the 92 citations retrieved from the original search, a total of 8 studies were included in this review (117 participants). No significant difference was noted between NCS and SCG with respect to the maximum percent decrease in FEV1 (WMD = -0.88; 95% CI: -4.50, 2.74), complete protection (i.e. maximum % fall FEV1 still =>10%); OR = 0.95; 95% CI: 0.50 to 1.8, clinical protection (i.e. < 50% improvement over placebo); OR = 0.71; 95% CI: 0.36 to 1.39; unpleasant taste (OR = 6.85; 95% CI: 0.77, 60.73), or sore throat (OR = 3.46; 95% CI: 0.32, 37.48). For these pooled comparisons, no statistically significant heterogeneity was identified. Subgroup analyses based on age, dosage of medications and timing of exercise post-inhalation were consistent with the overall pooled analyses.
Reviewer's conclusions: No significant differences were evident between the effect of NCS and SCG during the immediate post-exercise period in adults and children with EIB with regards to pulmonary function - specifically maximum percent decrease in FEV1, complete protection, clinical protection, or side effects.