BACKGROUND: Sodium cromoglycate has been recommended as maintenance treatment for childhood asthma for many years. Its use has decreased since 1990, when inhaled corticosteroids became popular, but it is still used in many countries.
OBJECTIVES: To determine the efficacy of sodium cromoglycate compared to placebo in the prophylactic treatment of children with asthma.
SEARCH STRATEGY: We searched the Cochrane Airways Group Asthma trials register (November 2002), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2002), MEDLINE (January 1966 to November 2002), EMBASE (January 1985 to November 2002) and reference lists of articles. We also contacted the pharmaceutical company manufacturing sodium cromoglycate
SELECTION CRITERIA: All double-blind placebo-controlled randomised trials, which addressed the effectiveness of inhaled sodium cromoglycate as maintenance therapy, studying children aged 0 up to 18 years with asthma.
DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality and extracted data. Study results were pooled.
MAIN RESULTS: Of 3500 titles retrieved from the literature, 25 papers reporting on 24 studies could be included in the review. The studies were published between 1970 and 1997 and together included 1074 participants. Most were cross-over studies. Few studies provided sufficient information to judge the concealment of allocation. Four studies provided results for the proportion of symptom-free days. Pooling the results did not reveal a statistically significant difference between sodium cromoglycate and placebo. For most of the other outcomes, the results were similar: small effect size and a confidence interval including the point of no difference. The funnel plot showed an under representation of small studies with negative results, suggesting publication bias.
REVIEWER'S CONCLUSIONS: The evidence of the efficacy of sodium cromoglycate over placebo is not proven. Publication bias is likely to have overestimated the beneficial effects of sodium cromoglycate as maintenance therapy in childhood asthma.