Differing effects of pethidine and morphine on human sphincter of Oddi motility

Abstract

Abstract The aim of this study was to evaluate the effects of morphine and pethidine on human sphincter of Oddi motility. The action of these opioids on the sphincter of Oddi was evaluated by means of intraoperative manometry in 36 patients undergoing elective cholecystectomy. Both opioids were given in intravenous cumulative equipotent doses up to a maximum of 10 μg/kg morphine or 100 μg/kg pethidine. At these doses, morphine increased the mean(s.d.) frequency of contractions from 2·4(1·0) to 7·9(1·6) (P < 0·001); this effect was reduced by naloxone (0·04 mg bolus, P < 0·05). Pethidine inhibited the frequency of contractions from 1·5(0·8) to 0·8(0·5) (P < 0·05); this response was blocked by atropine (0·6 mg bolus, P < 0·01). Pretreatment with atropine or naloxone reduced the frequency of contractions significantly (P < 0·05). The results illustrate different responses to pethidine and morphine of the sphincter of Oddi, and provide a pharmacological explanation for the suitability of pethidine over morphine as the analgesic of choice in patients experiencing biliary pain.