BACKGROUND: Recent meta-analyses suggested diclofenac may be superior to indomethacin in preventing post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP). The aim of our study was to compare the efficacy of 100 mg rectal indomethacin versus diclofenac on PEP incidences. DESIGN: This multicentre, double-blinded, randomised controlled trial was conducted in nine tertiary centres in China. Patients with low and high risk for PEP and native papilla were randomly allocated (1:1) to receive 100 mg diclofenac or 100 mg indomethacin rectally before ERCP. The primary outcome was the occurrence of PEP defined by the Cotton consensus. The intention-to-treat principle was conducted for the analysis. RESULTS: The trial was terminated early for futility after the predetermined first interim analysis. Between June 2023 and May 2024, 1204 patients were randomised into the diclofenac group (n=600) or indomethacin group (n=604). Baseline characteristics were balanced. The primary outcome occurred in 53 patients (8.8%) of 600 patients allocated to the diclofenac group and 37 patients (6.1%) of 604 patients allocated to the indomethacin group (relative risk 1.44
95% CI 0.96 to 2.16, p=0.074). PEP occurred in 35 (14.2%) of 247 high-risk patients in the diclofenac group and 26 (9.8%) of 266 high-risk patients in the indomethacin group (p=0.124). PEP incidences were also comparable in low-risk patients between the two groups (18/353 (5.1%) vs 11/338 (3.3%), p=0.227). Other ERCP-related complications did not differ between the two groups. CONCLUSION: Pre-procedure 100 mg rectal diclofenac was not superior to the same dose of rectal indomethacin regarding preventing PEP. These findings supported current clinical practice guidelines of 100 mg indomethacin or diclofenac for PEP prophylaxis in patients without contraindications. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov (NCT05947461).