INTRAVENOUS VERSUS INTRAPERITONEAL MORPHINE BEFORE SURGERY TO PROVIDEPOSTOPERATIVE PAIN RELIEF

Background: Opioid receptors have been demonstrated on peripheral affe rent nerves throughout the body. The aim of the present study was to c ompare the effects of intravenous and intraperitoneal administration o f morphine with regard to pain, postoperative morphine requirement, an d recovery after major abdominal surgery, and to describe the pharmaco kinetics of intraperitoneal morphine in humans. Methods: In a double-b lind manner, 30 patients scheduled for major abdominal surgery were ra ndomized to either 50 mg of morphine intravenously (IV) or 50 mg of mo rphine intraperitoneally (IF) before operation. Pain was measured on a visual analogue scale and morphine requirements were registered for 3 days. Recovery was measured as time to oral intake of food, time to f latulence and days in hospital. Plasma morphine, morphine-3-glucuronid e, and morphine-6-glucuronide concentrations were determined during th e first 4 h after morphine administration. Results: During the first p ostoperative hours there was less pain at rest (P=0.02) and on coughin g (P=0.004) in the intravenous group. The requirement of additional mo rphine (P=0.016) was lower in the intravenous group during the first p ostoperative day. No major differences in recovery were seen. The plas ma concentrations of morphine measured as area under the curve (AUG) d uring the first 4 h were similar, but the intravenous group showed sig nificantly higher concentrations of the active metabolite morphine-6-g lucuronide, (P=0.016), indicating a difference in pharmacokinetics aft er intraperitoneal compared to intravenous administration of morphine. Conclusion: Intraperitoneal administration of 50 mg of morphine befor e major abdominal surgery is less efficient in reducing pain and posto perative morphine requirements than the same amount of morphine given intravenously.