Nalmefene or naloxone for preventing intrathecal opioid mediated side effects in cesarean delivery patients

This study was designed to evaluate the efficacy of nalmefene vs. naloxone in preventing side effects resulting from intrathecal opioids, in patients undergoing cesarean delivery. Eighty patients who were scheduled for elective cesarean delivery under spinal anesthesia were included in a double-blind, placebo-controlled study. Patients were randomized into four groups: saline; intravenous nalmefene 0.25 mu g.kg(-1) every 12 h x 2; intravenous nalmefene 0.5 mu g.kg(-1) every 12 h x 2; and naloxone infusion 48 mu g.h(-1) (1.2 mu g.ml(-1)). There were no significant differences among the groups with respect to pain, sedation, satisfaction, or the occurrence or treatment of pruritus or nausea. There was a significant difference among the groups with respect to the occurrence of vomiting (P<0.03): both nalmefene groups had a higher rate of vomiting than did the control group; the 0.25 mu g.kg(-1) nalmefene group had a higher rate than did the naloxone group. The use of narcotic antagonists does not result in improved comfort in obstetrical patients receiving intrathecal morphine and fentanyl.