Oral 5-aminosalicylic acid for maintenance of remission in ulcerative colitis.

Background: Oral 5-aminosalicylic acid (5-ASA; also known as mesalazine or mesalamine) preparations were intended to avoid the adverse effects of sulfasalazine (SASP) while maintaining its therapeutic benefits. In an earlier version of this review, we found that 5-ASA drugs were more effective than placebo for maintenance of remission of ulcerative colitis (UC), but had a significant therapeutic inferiority relative to SASP. In this version, we have rerun the search to bring the review up to date.

Objectives: To assess the efficacy, dose-responsiveness, and safety of oral 5-ASA compared to placebo, SASP, or 5-ASA comparators for maintenance of remission in quiescent UC and to compare the efficacy and safety of once-daily dosing of oral 5-ASA with conventional (two or three times daily) dosing regimens.

Search Methods: We performed a literature search for studies on 11 June 2019 using MEDLINE, Embase, and the Cochrane Library. In addition, we searched review articles and conference proceedings.

Selection Criteria: We included randomized controlled trials with a minimum treatment duration of six months. We considered studies of oral 5-ASA therapy for treatment of participants with quiescent UC compared with placebo, SASP, or other 5-ASA formulations. We also included studies that compared once-daily 5-ASA treatment with conventional dosing of 5-ASA and 5-ASA dose-ranging studies.

Data Collection And Analysis: We used standard methodological procedures expected by Cochrane. The primary outcome was the failure to maintain clinical or endoscopic remission. Secondary outcomes were adherence, adverse events (AE), serious adverse events (SAE), withdrawals due to AEs, and withdrawals or exclusions after entry. Trials were separated into five comparison groups: 5-ASA versus placebo, 5-ASA versus SASP, once-daily dosing versus conventional dosing, 5-ASA (balsalazide, Pentasa, and olsalazine) versus comparator 5-ASA formulation (Asacol and Salofalk), and 5-ASA dose-ranging. We calculated the risk ratio (RR) and 95% confidence interval (CI) for each outcome. We analyzed data on an intention-to-treat basis, and used GRADE to assess the overall certainty of the evidence.

Main Results: The search identified 44 studies (9967 participants). Most studies were at low risk of bias. Ten studies were at high risk of bias. Seven of these studies were single-blind and three were open-label. 5-ASA is more effective than placebo for maintenance of clinical or endoscopic remission. About 37% (335/907) of 5-ASA participants relapsed at six to 12 months compared to 55% (355/648) of placebo participants (RR 0.68, 95% CI 0.61 to 0.76; 8 studies, 1555 participants; high-certainty evidence). Adherence to study medication was not reported for this comparison. SAEs were reported in 1% (6/550) of participants in the 5-ASA group compared to 2% (5/276) of participants in the placebo group at six to 12 months (RR 0.60, 95% CI 0.19 to 1.84; 3 studies, 826 participants; low-certainty evidence). There is probably little or no difference in AEs at six to 12 months' follow-up (RR 0.93, 95% CI 0.73 to 1.18; 5 studies, 1132 participants; moderate-certainty evidence). SASP is more effective than 5-ASA for maintenance of remission. About 48% (416/871) of 5-ASA participants relapsed at six to 18 months compared to 43% (336/784) of SASP participants (RR 1.14, 95% CI 1.03 to 1.27; 12 studies, 1655 participants; high-certainty evidence). Adherence to study medication and SAEs were not reported for this comparison. There is probably little or no difference in AEs at six to 12 months' follow-up (RR 1.07, 95% CI 0.82 to 1.40; 7 studies, 1138 participants; moderate-certainty evidence). There is little or no difference in clinical or endoscopic remission rates between once-daily and conventionally dosed 5-ASA. About 37% (717/1939) of once-daily participants relapsed over 12 months compared to 39% (770/1971) of conventional-dosing participants (RR 0.94, 95% CI 0.88 to 1.01; 10 studies, 3910 participants; high-certainty evidence). There is probably little or no difference in medication adherence rates. About 10% (106/1152) of participants in the once-daily group failed to adhere to their medication regimen compared to 8% (84/1154) of participants in the conventional-dosing group (RR 1.18, 95% CI 0.72 to 1.93; 9 studies, 2306 participants; moderate-certainty evidence). About 3% (41/1587) of participants in the once-daily group experienced a SAE compared to 2% (35/1609) of participants in the conventional-dose group at six to 12 months (RR 1.20, 95% CI 0.77 to 1.87; moderate-certainty evidence). There is little or no difference in the incidence of AEs at six to 13 months' follow-up (RR 0.98, 95% CI 0.92 to 1.04; 8 studies, 3497 participants; high-certainty evidence). There may be little or no difference in the efficacy of different 5-ASA formulations. About 44% (158/358) of participants in the 5-ASA group relapsed at six to 18 months compared to 41% (142/349) of participants in the 5-ASA comparator group (RR 1.08, 95% CI 0.91 to 1.28; 6 studies, 707 participants; low-certainty evidence).

Authors' Conclusions: There is high-certainty evidence that 5-ASA is superior to placebo for maintenance therapy in UC. There is high-certainty evidence that 5-ASA is inferior compared to SASP. There is probably little or no difference between 5-ASA and placebo, and 5-ASA and SASP in commonly reported AEs such as flatulence, abdominal pain, nausea, diarrhea, headache, and dyspepsia. Oral 5-ASA administered once daily has a similar benefit and harm profile as conventional dosing for maintenance of remission in quiescent UC.