The use of antioxidant agents is suggested as a complementary therapy in UC patients for the prevention of flares. Considering the potent antioxidant activity of N-acetylcysteine (NAC), in the present study we aimed to assess the effect of this supplement on remission maintenance in patients with ulcerative colitis (UC).

In the present double-blind randomized controlled clinical trial, 168 volunteer UC patients who were on high dose corticosteroid and Mesalamine for flare-up management, were recruited. The patients received 800 mg NAC or placebo for 16 weeks. Simultaneously, the prednisolone dose was tapered. The patients were followed up six more weeks post-intervention. The primary efficacy of the treatment was remaining in remission. The secondary outcomes were the endoscopic relapse, serum level of hs-CRP, hemoglobin, and fecal calprotectin level.

During 22 weeks follow up, 25 patients experienced relapses, six of them were in the NAC group and 19 of them were in the placebo group. There was a significant difference between the NAC and placebo groups regarding the relapse-free period (P = 0.007). Compared with the NAC group, significantly more patients in the placebo group had an endoscopic relapse (p < 0.001). At the end of the intervention period (16 weeks) and 6 weeks post-intervention, the mean fecal calprotectin, serum erythrocyte sedimentation rate, and hs-CRP levels were significantly lower in the NAC group compared with the placebo group (p < 0.05).

The findings indicated that NAC had a significantly more positive effect on the maintenance of remission compared with placebo in UC patients that were in the steroid-tapering phase of therapy.