Background & Aim: Recent studies have suggested the therapeutic effect of antimicrobial agents on primary sclerosing cholangitis (PSC). Therefore, we aimed to evaluate the efficacy of oral vancomycin in patients with PSC.

Method: A triple blinded, randomized, placebo-controlled trial was performed on 29 patients (2015-2016) in the Imam Khomeini Hospital, Tehran, Iran (NCT02605213). Patients were divided into two groups by simple randomization method: placebo 11 (37.9%)/vancomycin 18 (62.1%) and were treated with oral vancomycin (125 mg, four times a day) for 12 weeks. All patients in both groups simultaneously underwent treatment with ursodeoxycholic acid (UDCA, 300 mg, three times a day) before and during the study. Patients’ laboratory data and clinical symptoms were recorded at the beginning, first and third month after starting treatment, and the response to treatment was analyzed.

Results: 29 patients with a mean age of 36.27±10.60 years were included in the study. Primary endpoints were accomplished in the vancomycin group showing a significant decline in the mean level of PSC Mayo risk score (decrease rate 3rd month-baseline=-322.03%, p= 0.026) during follow up time. Moreover, the analysis of the level of alkaline phosphatase (ALP) in the vancomycin group showed a significant decrease in the third month of treatment as compared to its level in the first month (mean difference 3rd month-1st month=-142.92, Decrease rate=-18.24%, p= 0.02). Among secondary endpoints, erythrocyte sedimentation rate (p= 0.005), gamma-glutamyl transpeptidase (p= 0.02) and patients’ symptoms including fatigue, pruritus, diarrhea and anorexia showed a significant decrease in the vancomycin group. Conclusion: This study demonstrated an acceptable efficacy of vancomycin in the treatment of PSC.