OPRK1 and irritable bowel syndrome: Opioid receptor agents—Eluxadoline is a mu- and kappa-opioid receptor agonist and delta-opioid receptor antagonist that has demonstrated efficacy in managing bowel habit changes and abdominal pain in diarrhea-predominant IBS.204Serotonin receptor modulators—Several serotonin receptor modulating agents also have the potential to help, though they have not been rigorously studied specifically in human forms of IBD.