Allopurinol to prevent pancreatitis after endoscopic retrograde cholangiopancreatography: a randomized placebo-controlled trial

Endoscopic retrograde cholangiopancreatography (ERCP) is associated with a risk of pancreatitis (PEP). Animal studies suggest that (single-dose) allopurinol (xanthine oxidase inhibitor with high oral bioavailability and long-lasting active metabolites) may reduce this risk; human study results are conflicting. The aim of this study was to determine if allopurinol decreases the rate of PEP.

Patients referred for ERCP to 9 endoscopists at 2 tertiary centers were randomized to receive either allopurinol 300 mg or identical placebo orally 60 minutes before ERCP, stratified according to high-risk ERCP (manometry or pancreatic therapy). The primary outcome (PEP) was adjudicated blindly; pancreatitis was defined according to the Cotton consensus, and evaluated at 48 hours and 30 days. Secondary outcomes included severe PEP, length of stay, and mortality (nil). The trial was terminated after the blinded (midpoint) interim analysis, as recommended by the independent data and safety monitoring committee.

We randomized 586 subjects, 293 to each arm. The crude PEP rates were 5.5% (allopurinol) and 4.1% (placebo), (P = .44; difference = 1.4%; 95% confidence interval, -2.1% to 4.8%). The Mantel-Haenszel combined risk ratio for PEP with allopurinol, considering stratification, was 1.37 (95% confidence interval, 0.65-2.86). Subgroup analyses suggested nonsignificant trends toward possible benefit in the high-risk group, and possible harm for the remaining subjects. Logistic regression found pancreatic therapy, pancreatic injection, and prior PEP to be the only independent predictors of PEP.

Allopurinol does not appear to reduce the overall risk of PEP; however, its potential benefit in the high-risk group (but potential harm for non-high-risk patients) means further study is required.