Meperidine vs Morphine in Pancreatitis and Cholecystitis

Every third-year medical student on the general surgery clerkship learns from the intern to prescribe meperidine hydrochloride instead of morphine sulfate as an analgesic for patients with pancreatitis and cholecystitis. The Washington Manual of Medical Therapeutics recommends meperidine for these patients because, "it has no significant effect on the sphincter of Oddi."¹ Standard references like Goodman and Gilman's Pharmacological Basis of Therapeutics² perpetuate the idea of possible pancreatic complications from sphincter of Oddi spasm with morphine without giving the primary reference. An extensive literature search failed to find the basis for the preference of meperidine over morphine in patients with cholecystitis and pancreatitis. We speculate that this prejudice against morphine might possibly be based on old case reports, beginning with Walters et al.³ Although human studies show that morphine causes increases in sphincter of Oddi pressure,⁴ clinical evidence does not link morphine with increased risk over other opioids in relation to causing or aggravating pancreatitis or cholecystitis. In a study comparing equianalgesic doses of morphine and meperidine in 40 patients undergoing cholecystectomy, meperidine raised the common bile duct pressure 14% more than morphine.⁵