Butyrate represents the main source of energy for colonic epithelial cells; however, its availability/utilization is impaired in ulcerative colitis (UC). In the present randomized, double-blind, placebo-controlled pilot study, the safety and efficacy of colonic targeted oral sodium butyrate tablets, coated with a pH-dependent soluble polymer, have been evaluated in ulcerative colitis. Thirty patients with mild to moderate colitis underwent a six-week course of oral sodium butyrate (4 g/day) plus oral mesalazine (2.4 g/day), (Group A) or of oral mesalazine plus placebo (Group B). Clinical, endoscopic, and histologic data were collected at the beginning and the end of the study. Twenty-five patients completed the study (12 in group A, 13 in group B). No untoward side effects were reported. In group A, seven patients underwent remission and four improved; in Group B the numbers were 5 and 5, respectively. After treatment, all clinical parameters had significantly improved in both treatment arms compared to pretreatment findings. The UC disease activity index (UCDAI) score decreased from 7.27 +/- 2.02 to 2.58 +/- 2.19 (P < 0.05) in the combined treatment group and from 6.07 +/-1.60 to 3.46 +/- 1.98 (P < 0.05) in group B. The endoscopic and histologic scores also significantly improved after treatment in both groups (P < 0.05). The difference between the two treatment arms was not significant, but a significantly better improvement vs baseline values (P < 0.05) was observed in the combined treatment group vs the mesalazine group, when considering both the clinical index (delta9.58 +/- 4.19 vs 5.92 +/- 3.48) and the UCDAI score (delta4.67 +/- 2.19 vs 2.54 +/- 2.18). A more favorable trend, although not significant, was observed for all individual parameters in group A. In conclusion, results of the present pilot study indicate that oral butyrate is safe and well tolerated. These data also suggest that oral butyrate may improve the efficacy of oral mesalazine in active ulcerative colitis and prompt the need of a large scale investigation to confirm the present findings.