The effects of naloxone associated with the intrathecal use of morphine in labor.

The efficacy of naloxone in reducing the incidence of side effects after intrathecal injection of morphine and the effects of maternal naloxone administration on the condition of the newborn were evaluated in 40 patients. Patients in labor were given a 1-mg intrathecal injection of morphine and, 1 hr later, either a 0.4-mg bolus of naloxone, followed by a 0.4-0.6 mg/hr intravenous infusion of naloxone, or an intravenous bolus of saline, followed by an intravenous infusion of saline. Intrathecal morphine provided at least 50% pain relief in 78% of patients given naloxone, and in 82% given saline. Intravenous naloxone significantly decreased the incidence of pruritus during labor and delivery. There was no significant decrease in the incidence of nausea, vomiting, somnolence, dizziness, or urinary retention in patients given naloxone. Despite placental transfer of naloxone, neonatal outcome was not adversely affected. For both groups, maternal beta-endorphin levels decreased significantly with the onset of analgesia and returned to control levels at delivery. We conclude that intravenous infusion of naloxone reduced pruritus after intrathecal injection of 1 mg of morphine for labor pain without lessening analgesia or adversely affecting maternal or neonatal status.

Intrathecal administration of hyperbaric morphine for the relief of pain in labour.

Thirty healthy women in active labour received an intrathecal injection of morphine 0.5 mg (n = 12) or 1 mg (n = 18) in 7.5% dextrose. Both doses provided excellent analgesia for labour, 93% of patients obtaining at least 50% pain relief. Analgesia began 15-60 min after injection and did not decrease until 6-8 h after injection. Analgesia was satisfactory until distension of the perineum, either by forceps or the infant's head. The intrathecal injection of morphine did not adversely affect the condition of the infant. Eighty per cent of patients developed pruritus; 53%, nausea or vomiting, or both; 43%, urinary retention; and 43%, drowsiness. These side effects were decreased by naloxone, which did not affect the degree of analgesia. There was no significant depression of ventilation in any patient. These results suggest that morphine 0.5 mg or 1 mg, administered intrathecally, effectively decreases the pain of labour, and that i.v. administration of naloxone can alleviate the common side effects.