A COMPARISON OF INTRATHECAL MORPHINE-6-GLUCURONIDE AND INTRATHECAL MORPHINE-SULFATE AS ANALGESICS FOR TOTAL HIP-REPLACEMENT

Postoperative analgesia was assessed after intrathecal administration of morphine-6-glucuronide (M6G) 100 mu g and 125 mu g in 75 patients u ndergoing total hip replacement. Analgesia was excellent and was simil ar to that obtained after intrathecal administration of morphine sulfa te 500 mu g. Visual analog pain scores recorded postoperatively were l ow (median = 0) and were similar in all three groups. However, at 6 an d 10 h after operation significantly more patients in the M6G 125 grou p recorded pain as 0 compared with patients in the morphine group (P < 0.04, P < 0.01) and significantly more patients in the M6G 100 group recorded pain as 0 at 24 h after operation compared with patients in t he morphine group (P < 0.04). Postoperative meperidine consumption usi ng a patient-controlled system was also similar in each of the three t reatment groups. Nausea and emesis occurred frequently in all groups; morphine (nausea 88%, vomiting 76%), M6G 100 mu g (nausea 76%, vomitin g 64%), and M6G 125 mu g (nausea 88%, vomiting 60%). Respiratory depre ssion occurred in two and three patients, respectively, in the M6G 100 -mu g and 125-mu g groups but did not occur in any patient who receive d morphine sulfate. The lack of statistical significance in the differ ence in incidence of respiratory depression between the groups may rep resent a type II error. However, the risk of late respiratory depressi on developing after administration of any intrathecal opioid necessita tes careful postoperative observation of patients. As M6G is a potent intrathecal analgesic further investigation of this drug using small d oses may be useful.