Clinical bottom line
Inhaled sodium cromoglycate (SCG) remains a putative option for preventing exercise-induced bronchoconstriction (EIB) in athletes, with evidence supporting modest bronchoprotective effects. While SCG can reduce airway hyperresponsiveness triggered by exercise or inhaled stimuli, its efficacy appears generally inferior or comparable to nedocromil sodium, a related cromone agent. The clinical benefit of SCG in EIB prevention is modest and variable, warranting cautious interpretation and individualized consideration. Current evidence is largely derived from older studies, and SCG’s role should be contextualized within broader asthma and EIB management strategies.
What the evidence shows
Sodium cromoglycate, an inhaled mast cell stabilizer, has been studied for its ability to prevent bronchoconstriction induced by exercise and inhaled provocations. Early clinical investigations demonstrated that SCG can attenuate airway narrowing following exercise and inhalation of bronchoconstrictive agents such as adenosine 5'-monophosphate (AMP) and sodium metabisulphite (Dahl et al., 1980; Dixon et al., 1990; Phillips et al., 1989). These studies suggest SCG acts by inhibiting mediator release from airway mast cells, thereby reducing airway hyperresponsiveness.
A Cochrane systematic review by Kelly et al. (2000) compared SCG with nedocromil sodium for EIB prevention. The review concluded that both agents reduce the severity of exercise-induced bronchoconstriction, but nedocromil sodium may offer slightly greater protection. Similarly, Kelly et al. (2001) in a European Respiratory Journal systematic review reaffirmed that while both cromones are effective, nedocromil sodium tends to have superior efficacy against EIB.
Additional comparative studies in children with asthma showed that SCG’s protective effect against exercise-induced bronchoconstriction is less potent than that of some alternative agents such as verapamil or ipratropium bromide, although SCG remains beneficial (Boner et al., 1987). The bronchoprotective effect of SCG is generally observed when inhaled shortly before exercise, highlighting the importance of timing in clinical use.
Caveats and uncertainty
The bulk of evidence supporting SCG’s role in EIB prevention comes from studies conducted in the 1980s and 1990s, limiting applicability to current practice where newer agents and inhaler technologies have emerged. The magnitude of SCG’s effect is modest and variable across individuals, and it may be insufficient as monotherapy for athletes with moderate to severe EIB or underlying asthma.
Direct head-to-head comparisons with contemporary inhaled corticosteroids or leukotriene receptor antagonists are lacking, which limits understanding of SCG’s relative place in therapy. Furthermore, the optimal dosing regimen and duration of protection remain incompletely defined. Some studies suggest that SCG’s protective effect may wane within a few hours post-inhalation, necessitating repeated dosing for sustained benefit.
Adherence challenges and the need for pre-exercise administration may reduce practicality for some athletes. Finally, SCG does not treat underlying airway inflammation and should not replace controller therapies in asthma management.
How this may change practice
For pulmonologists and sports medicine clinicians managing athletes with EIB, inhaled sodium cromoglycate may be considered a supplementary option for bronchoprotection, particularly in patients who prefer non-steroidal therapies or have mild symptoms. Its use could be integrated as a pre-exercise prophylactic inhaler in select cases, especially when other agents are contraindicated or not tolerated.
However, given the modest efficacy and dated evidence base, SCG should not supplant established controller medications or rescue bronchodilators. Clinicians should counsel patients on the timing of administration and set realistic expectations regarding symptom control. Further research is needed to clarify SCG’s comparative effectiveness against newer therapies and to optimize dosing strategies.
In summary, inhaled sodium cromoglycate remains a putative, adjunctive therapy for EIB prevention in athletes, warranting individualized consideration and further validation in contemporary clinical contexts.