The effects of continuous intravenous naloxone on epidural morphine analgesia

Forty-five patients undergoing Caesarean section under epidural anesthesia with bupivacaine were randomly allocated to three groups. Group 1 received 4 mg of epidural morphine immediately postoperatively and 2 mg naloxone by intravenous infusion for 12 hours postoperatively; group 2 was treated as group 1 but without naloxone infusion; group 3 received 10 mg morphine intramuscularly and 20 ml epidural saline after delivery of the baby. Epidural morphine 4 mg produced better postoperative analgesia than 10 mg of morphine intramuscularly (p less than 0.001) and the intravenous infusion of naloxone did not ablate the analgesic effects of epidural morphine. The incidence of itching and vomiting was higher in the epidural opioid groups (p less than 0.05) and intravenous naloxone, although it reduced the severity of the itching, did not reduce its overall incidence. Respiratory depression was not detected in any of the three groups.