Background  Rectally administered mesalazine (mesalamine; 5-aminosalicylic acid) is the first-line therapy for treatment of distal ulcerative colitis. Recently, a high-volume 5-aminosalicylic acid foam has been shown to be as effective and safe as standard 5-aminosalicylic acid enema.

Aim  To study the efficacy and safety of a low-volume vs. a high-volume 5-aminosalicylic acid foam.

Methods  In this investigator-blinded study, patients with active distal ulcerative colitis [Clinical Activity Index (CAI) > 4, Endoscopic Index ≥ 4] were randomized to receive 2 × 1 g/30 mL low-volume (= 163) or 2 × 1 g/60 mL high-volume 5-aminosalicylic acid foam (= 167) for 42 days. Primary end point was clinical remission (CAI ≤ 4) at the final/withdrawal visit (per-protocol).

Results  330 patients were evaluable for efficacy and safety by intention-to-treat, 290 for per-protocol analysis. Clinical remission rates at week 6 (per-protocol) were 77% on low-volume foam vs. 77% on high-volume foam (= 0.00002 for non-inferiority). The low-volume foam was associated with a lower frequency of severe discomfort, pain and retention problems.

Conclusions  Low-volume 5-aminosalicylic acid foam is as effective and safe as a high-volume 5-aminosalicylic acid foam in the treatment of active distal ulcerative colitis, but offers compliance advantages compared to the high-volume preparation.