Background: To summarize and quantify the evidence supporting rectal 5- or 4-aminosalicylate (ASA) therapies for disease exacerbation or remission maintenance in distal ulcerative colitis, we performed a meta-analysis.

Methods: All randomized, double-blind controlled trials involving aminosalicylate therapy were retrieved from a MEDLINE search, review articles on ulcerative colitis therapy or their bibliographies. Of 55 studies retrieved, 19 met the inclusion criteria. Appraisal and data extraction were performed by two observers and scoring disagreements were resolved by consensus.

Results: Eleven trials tested 5-ASA and three tested 4-ASA in active ulcerative colitis. 5-ASA was superior to placebo for inducing remission or symptomatic improvement in active ulcerative colitis with a pooled odds ratio of 7.36 (95% Confidence interval (CI): 4.72–11.47). In four trials the pooled odds ratio for endoscopic improvement was 10.04 (95 % CI: 5.72–17.61) and for histological improvement 10.31 (95% CI: 5.85–18.18). Studies evaluating 4–ASA suggest a benefit similar to prednisolone in treating active disease. Five trials assessed remission maintenance with 5-ASA, and when compared to placebo gave a pooled odds ratio of 16.22 (95% CI: 4.71–55.92). No dose-response relationship was observed. ASA compounds were not therapeutically superior to other treatments.

Conclusions: We conclude that rectal 5-ASA is effective therapy for active distal ulcerative colitis. More trials are needed to assess 4-ASA, dose-response effects and the ideal regimen for remission maintenance.