Effects of prophylactic nalmefene on the incidence of morphine-related side effects in patients receiving intravenous patient-controlled analgesia

Background: Opioid-related side effects associated with intravenous patient -controlled analgesia can be reduced by a low-dose naloxone infusion, The i nfluence of nalmefene, a pure opioid antagonist with a longer duration of a ction, on opioid-related side effects has not been evaluated. This study wa s designed to determine the dose-response relation for nalmefene for the pr evention of morphine-related side effects in patients receiving intravenous patient-controlled analgesia. Methods; One hundred twenty women undergoing lower abdominal surgery were e nrolled in the study. General anesthesia was induced using thiopental and r ocuronium and maintained with desflurane, nitrous oxide, and fentanyl or su fentanil All patients received neostigmine and glycopyrrolate to reverse re sidual neuromuscular blockade. No prophylactic antiemetics were administere d. At the end of surgery, patients were randomized to receive saline, 15 mu g nalmefene, or 25 mu g nalmefene intravenously. The need for antiemetic a nd antipruritic drugs and the total consumption of morphine during the 24-h study were recorded. The incidences of postoperative nausea, vomiting, pru ritus, and pain were recorded 30 min after patients were admitted to the po stanesthesia care unit. in addition, patient remembrance of these side effe cts was noted at 24 h after operation, Results: The need for antiemetic and antipruritic medications during the 24 -h study period was significantly lower in the patients receiving nalmefene compared with those receiving placebo. However, the need to treat side eff ects was similar in the two nalmefene groups, Prophylactic administration o f nalmefene reduced the patients remembrance of nausea and itching as asses sed 24 h after operation. Although the total consumption of morphine during the 24-h study period was similar in the three groups, retrospectively pat ients who received nalmefene characterized their pain as less severe in the previous 24 h, Conclusion: Compared with placebo, prophylactic administration of nalmefene significantly decreased the need for antiemetics and antipruritic medicati ons in patients receiving intravenous patient-controlled analgesia with mor phine.