Objective: Traditional teaching dictates that morphine induces "spasm" in the sphincter of Oddi (SO) and should not be used in acute pancreatitis and that meperidine is the analgesic of choice because it does not elevate SO pressures. A literature search and review was performed to evaluate this teaching examining the effect of narcotic analgesic's effects on SO.
Methods: A Medline search was performed using keywords and phrases. The manufacturers of meperidine were contacted and their reports and studies were obtained and reviewed.
Results: Initial studies measured biliary pressure after narcotic administration in animals, and postoperative and intraoperative cholecystectomy patients. All narcotics increased biliary pressure, but morphine was associated with the largest elevation. Later studies using endoscopic retrograde cholangiopancreatography with direct SO manometry demonstrated that the SO is exquisitely sensitive to all narcotics including meperidine and that a small increase in biliary sphincter pressure is seen with higher doses of morphine. All narcotics increase SO phasic wave frequency and interfere with SO peristalsis.
Conclusions: Narcotic-induced increases in phasic wave frequency interfere with SO filling and are responsible for the increase in bile duct pressure seen on the initial studies. No studies directly compare the effects of meperidine or morphine on SO manometry and no comparative studies exist in patients with acute pancreatitis. No outcome-based studies comparing these drugs have been performed in patients with acute pancreatitis. Morphine may be of more benefit than meperidine by offering longer pain relief with less risk of seizures. No studies or evidence exist to indicate morphine is contraindicated for use in acute pancreatitis.