Objective Indigo naturalis (IN) is a traditional Chinese medicine that has recently been reported to be effective for ulcerative colitis (UC). The aim of this study was to evaluate the efficacy and safety of IN. Methods We performed a retrospective observational study for 14 patients with UC treated with IN from October 2015 to December 2016. Results After 8 weeks of oral administration of IN, the partial Mayo score decreased from 4 (2-5) to 1.5 (0-4) [median, interquartile range (IQR), p=0.015]. Among 10 active UC patients, 5 (50%) showed a clinical response, and 4 (40%) achieved clinical remission. Serial changes of endoscopic activity were evaluated in nine patients using the Mayo endoscopic subscore (MES), Rachmilewitz endoscopic index (REI), and UC endoscopy index of severity (UCEIS). The MES decreased from 2 (2-3) to 1 (1-2) [median (IQR), p=0.005], the REI decreased from 7 (5.5-11) to 3 (1-7) [median (IQR), p=0.008], and the UCEIS decreased from 3 (3-4.5) to 1 (0.5-3.5) [median (IQR), p=0.039]. One patient developed acute right-sided colitis with wall thickening and edematous change, and the remaining 13 showed no adverse events. Conclusion We conclude that IN is effective for patients with UC as a therapy for inducing remission.

Keywords: Chinese herbal medicine; Qing-Dai; indigo naturalis; ulcerative colitis.