COMPARISON OF ANALGESIC EFFICACY OF OXYCODONE AND MORPHINE IN POSTOPERATIVE INTRAVENOUS PATIENT-CONTROLLED ANALGESIA

Background: Morphine has been the standard opioid in patient-controlle d analgesia (PCA). Oxycodone, the analgesic potency of which in i.v. a dministration has been suggested to be slightly greater than that of m orphine, has not yet been studied for its efficacy in PCA. Methods: Fi fty patients, undergoing a plastic reconstruction of the breast or a m ajor operation of the vertebrae, such as lumbar spinal fusion, used PC A for postoperative pain. Patients were randomized to receive either m orphine 45 mu g/kg or oxycodone 30 mu g/kg as i.v. bolus doses. Patien ts were assessed for pain with a visual analogue scale (VAS) and side effects at 3, 9 and 24 h. Venous blood samples for the measurement of plasma concentration of oxycodone and that of morphine and its metabol ites were taken. Results: In this study patients needed, on average, t he same amount of oxycodone and morphine in the recovery room and on t he ward. There was no difference in the quality of analgesia (VAS) or incidence of side effects, such as nausea, vomiting, pruritus and urin ary retention. The plasma concentrations of morphine-6-glucuronide sho wed that this metabolite might contribute to the analgesia resulting f rom morphine administration. Conclusions: The same dose of intravenous oxycodone and morphine administered by PCA pump was needed for immedi ate postoperative analgesia. The two drugs appear to be equipotent.