Findings demonstrate the efficacy as well as safety of preprocedural rectal indomethacin administration in decreasing the incidence of post-extracorporeal shock wave lithotripsy (ESWL) pancreatitis.

• This double-blind, randomized, placebo-controlled trial included 1,370 patients aged 18 years or older with chronic pancreatitis and pancreatic stones (>5 mm in diameter) who were eligible for treatment with ESWL.

• Participants were randomized to receive 100 mg rectal indomethacin or identical glycerin (placebo) suppositories 30 min before ESWL.

• In the rectal indomethacin and placebo groups, post-ESWL pancreatitis developed in 9% and in 12% of the patients, respectively (relative risk 0·71).

• Transient adverse events occurred in 34% and 37% of the patients in the rectal indomethacin group and placebo group, respectively, with asymptomatic hyperamylasemia being the most common (28% vs 29%).

• The incidence of other complications and transient adverse events did not differ between groups.