Prevention of relapses is a major issue in the management of Crohn's disease. Corticosteroids, the mainstay of treatment of acute exacerbations are not effective in the maintenance of remission and its chronic use is limited by numerous adverse events. A number of randomised controlled trials comparing various 5-ASA agents with either placebo or other drugs have had conflicting results.
To conduct a systematic review to evaluate the efficacy of oral 5-ASA agents for the maintenance of medically-induced remission in Crohn's disease.
We searched MEDLINE (1966 to January 2004), EMBASE (1984-January 2004), the Cochrane Central Register of Controlled Trials from the Cochrane Library (Issue 1, 2004) and the IBD Review Group Specialized Trials Register. We hand-searched the articles cited in each publication.
We included randomised controlled trials which compared oral 5-ASA agents with either placebo or sulphasalazine, with treatment durations of at least 6 months.
Data collection and analysis
Data extraction and assessment of methodological quality of each study were independently performed by two reviewers. Any disagreement among reviewers was resolved by consensus. The main outcome measure was the occurrence of relapse as defined by the primary studies. Odds ratios of relapse rates and their 95% confidence intervals were calculated.
5-ASA versus placebo
In the main analysis, we used as the denominator the total number of patients randomised. We assumed that participants who dropped out of the study, and on whom there was no post withdrawal information, had relapsed during the study period. Using the fixed effects model, the odds ratio for 6 studies where participants were followed up for 12 months was 1.00 (95%CI, 0.80 to 1.24). Using the random effects model in a sensitivity analysis had little effect on the results with an OR of 0.93 (95% CI, 0.65 to 1.33). For the seventh study where follow up was for 24 months, the odds ratio was 0.98; 95% CI, 0.51 to 1.90. In further sensitivity analyses, we analysed only participants who completed the study and ignored the dropouts. The odds ratio (fixed effects model) for the 6 studies where follow up was for 12 months was 0.74 (95% CI, 0.57 to 0.96), but using the random effects model, the OR was 0.68 (95% CI 0.45 to 1.02). The OR for the seventh study where follow up was for 24 months (Gendre 1993a), was 0.86; 95% CI, 0.42 to 1.78.
5-ASA versus sulphasalazine
We did not find any study that satisfied the inclusion criteria.
We found no evidence in this review to suggest that 5-ASA preparations are superior to placebo for the maintenance of medically-induced remission in patients with Crohn's disease. Therefore it appears that additional randomised trials of this regime are not justified.