Oral 5-aminosalicylic acid for maintenance of surgically-induced remission in Crohn's disease.

BACKGROUND: The use of 5-aminosalicylates (5-ASAs) in Crohn's disease (CD) is controversial.  A recent Cochrane review found that 5-ASAs are not effective for the maintenance of medically-induced remission in CD, but their role in the maintenance of surgically-induced remission is unclear.

OBJECTIVES: The objectives were to evaluate the efficacy and safety of 5-ASA agents for the maintenance of surgically-induced remission in CD.

SEARCH STRATEGY: The search was standardised and not limited by language and included electronic searching (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Inflammatory Bowel Disease Group Specialized Trials Register), reference searching of all included studies, abstracts from major meetings, personal contacts and drug companies.

SELECTION CRITERIA: Randomised controlled trials (RCTs) which compared 5-ASAs with either placebo or another intervention, with treatment durations of at least 6 months were considered for inclusion. Participants were patients of any age with CD in remission following surgery. Primary outcome measures were clinical relapse or endoscopic recurrence as defined by the primary studies. Secondary endpoints were the occurrence of adverse events.

DATA COLLECTION AND ANALYSIS: Relevant papers were identified and the authors independently assessed the eligibility of trials. Methodological quality was assessed using the Cochrane risk of bias tool.The Cochrane RevMan software was used for analyses. Patients with final missing outcomes were assumed to have relapsed. Odds ratio (OR) and 95% confidence intervals (95% CI) were calculated based on the fixed effects model. The chi square and I(2) statistics were used to assess statistical heterogeneity.

MAIN RESULTS: Nine RCTs were included in the review. Seven studies compared oral 5-ASA with placebo and two compared oral 5-ASA with purine antimetabolites (azathioprine or 6-mercaptopurine). 5-ASA was significantly more effective than placebo for preventing relapse (OR 0.68, 95% CI, 0.52 to 0.90). There was no statistically significant heterogeneity among the 8 trials comparing 5-ASA with placebo (P=0.47). No statistically significant difference in adverse events was found for 5-ASA versus placebo (OR 1.02, 95%CI, 0.60 to 1.76). No statistically significant difference was found between 5-ASA and purine antimetabolites for preventing relapses (OR 1.08 95% CI, 0.63 to 1.85).

AUTHORS' CONCLUSIONS: The pooled analyses suggest that 5-ASA preparations may be superior to placebo for the maintenance of surgically-induced remission in patients with CD. The results of the pooled analyses should be interpreted with caution because adequately powered studies demonstrated no difference and publication bias (failure to publish negative studies) may be an issue. The potential benefit provided by 5-ASA drugs is modest with a number needed to treat of approximately 16 to 19 patients to avoid one relapse which raises issues about the cost-effectiveness of this therapy. However, 5-ASA drugs are safe and well tolerated. The incidence of adverse events was not different in patients receiving 5-ASA compared with those receiving placebo. There is insufficient evidence to allow any conclusions on how 5-ASA preparations compare with azathioprine or 6-mercaptopurine.