Tacrolimus as Prophylaxis of Post-ERCP Pancreatitis

The goal of this clinical trial is to learn if a single intravenous dose of tacrolimus, given before an ERCP procedure (an endoscopic procedure of the bile ducts and pancreas), can prevent post-ERCP pancreatitis (PEP) in adults at moderate-to-high risk of developing this complication. The main question it aims to answer is: * Does a single dose of tacrolimus lower the number of participants who develop pancreatitis after ERCP? Researchers will compare tacrolimus to a placebo (a look-alike solution with no active drug) to see if tacrolimus reduces the occurrence of PEP. Participants will: * Receive an intravenous infusion of either tacrolimus or placebo, given over 60 minutes, ending before the start of the ERCP procedure * Receive standard preventive treatment (a rectal anti-inflammatory medication (NSAID)) in addition to the study infusion * Be contacted by phone 48 hours after the procedure to check for symptoms * Complete questionnaires about quality of life and healthcare use, and be followed for 12 weeks after the procedure * The first 40 enrolled patients will have extra blood samples taken to measure tacrolimus levels.