Review question: What is the effect of prophylactic administration of cromolyn sodium on the incidence of chronic lung disease at 28 days or 36 weeks' postmenstrual age (PMA), mortality, or the combined outcome of mortality or chronic lung disease at 28 days or 36 weeks' PMA in preterm infants.
Background
Cromolyn sodium administered in the first few days of life has not been shown to prevent chronic lung disease in preterm infants. Preterm babies (babies born before 37 weeks' PMA) often need to be given oxygen for lung problems for many weeks because of chronic lung disease. This is due, in part, to inflammation (swelling) within the lungs. Theoretically, cromolyn sodium is a drug that might help prevent this inflammation. It is relatively safe and side effects are rare. It can be given by nebuliser or aerosol inhaler in the first few days of life to try to prevent chronic lung disease.
Study characteristics
We found only two studies enrolling 64 infants. In one of the two studies, there was a low risk of bias whereas in the second study there were concerns about how the infants had been put into treatment groups, and whether parents and doctors were aware of which treatment was given (random sequence generation, allocation concealment and blinding of outcomes assessment).
Study funding sources
We found no studies that received funding from the industry.
Key results
Prophylaxis with cromolyn sodium did not result in an important effect on the combined outcome of mortality or chronic lung disease at 28 days of age, chronic lung disease at 28 days; chronic lung disease at 28 days or at 36 weeks' PMA; or chronic lung disease in survivors at 28 days or at 36 weeks' PMA. This review of trials found no strong evidence that cromolyn sodium can prevent or reduce chronic lung disease and further research does not seem to be justified.
Quality of evidence
The quality of evidence was low for most measures.
There is currently no evidence from randomised trials that cromolyn sodium has a role in the prevention of CLD. Cromolyn sodium cannot be recommended for the prevention of CLD in preterm infants.
This is an update of a review last published by Cochrane in June 2012 entitled "Cromolyn sodium for the prevention of chronic lung disease in preterm infants", which included two studies. This 2016 update identified no further studies.
Chronic lung disease (CLD) frequently occurs in preterm infants and has a multifactorial aetiology including inflammation. Cromolyn sodium is a mast cell stabiliser that inhibits neutrophil activation and neutrophil chemotaxis and therefore may have a role in the prevention of CLD.
To determine the effect of prophylactic administration of cromolyn sodium on the incidence of CLD at 28 days or 36 weeks' postmenstrual age (PMA), mortality, or the combined outcome of mortality and CLD at 28 days or 36 weeks' PMA in preterm infants.
We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 4), MEDLINE via PubMed (1966 to 12 May 2016), Embase (1980 to 12 May 2016), and CINAHL (1982 to 12 May 2016). We searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.
We included randomised or quasi-randomised controlled clinical trials involving preterm infants. Initiation of cromolyn sodium administration was during the first two weeks of life. The intervention had to include administration of cromolyn sodium by nebuliser or metered dose inhaler with or without spacer device versus placebo or no intervention. Eligible studies had to include at least one of the following outcomes: overall mortality, CLD at 28 days, CLD at 36 weeks' PMA, or the combined outcome mortality and CLD at 28 days.
We used the standard method for Cochrane as described in the Cochrane Handbook for Systematic Reviews of Interventions. We reported risk ratio (RR) and risk difference (RD) with 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) with 95% CI for continuous data. The meta-analysis used a fixed-effect model. We examined heterogeneity using the I2 statistic. We assessed the quality of evidence for the main comparison at the outcome level using the GRADE approach.
We identified two eligible studies with small numbers of infants enrolled (64 infants). Prophylaxis with cromolyn sodium did not result in a statistically significant effect on the combined outcome of mortality and CLD at 28 days (typical RR 1.05, 95% CI 0.73 to 1.52; typical RD 0.03, 95% CI -0.20 to 0.27; 2 trials, 64 infants; I2 = 0% for both RR and RD); mortality at 28 days (typical RR 1.31, 95% CI 0.52 to 3.29; I2 = 73% typical RD 0.06, 95% CI -0.13 to 0.26; I2 = 87%; 2 trials, 64 infants) (very low quality evidence); CLD at 28 days (typical RR 0.93, 95% CI 0.53 to 1.64; I2 = 40%; typical RD -0.03, 95% CI -0.27 to 0.20; I2 = 38%; 2 trials, 64 infants) or at 36 weeks' PMA (RR 1.25, 95% CI 0.43 to 3.63; RD 0.08, 95% CI -0.29 to 0.44; 1 trial, 26 infants). There was no significant difference in CLD in survivors at 28 days (typical RR 0.97, 95% CI 0.58 to 1.63; typical RD -0.02, 95% CI -0.29 to 0.26; I2 = 0% for both RR and RD; 2 trials, 50 infants) or at 36 weeks' PMA (RR 1.04, 95% CI 0.38 to 2.87; RD 0.02, 95% CI -0.40 to 0.43; 1 trial, 22 infants). Prophylaxis with cromolyn sodium did not show a statistically significant difference in overall neonatal mortality, incidence of air leaks, necrotising enterocolitis, intraventricular haemorrhage, sepsis, and days of mechanical ventilation. There were no adverse effects noted. The quality of evidence according to GRADE was very low for one outcome (mortality to 28 days) and low for all other outcomes. The reasons for downgrading the evidence was due to design (risk of bias in one study), inconsistency between the two studies (high I2 values for mortality at 28 days for both RR and RD), and lack of precision of estimates (small sample sizes). Further research does not seem to be justified.