Controlled trial of extradural bupivacaine with fentanyl, morphine or placebo for pain relief in labour.

In a prospective, randomized double-blind study carried out on 255 parturients, fentanyl 80 micrograms (n = 81), morphine 4 mg (n = 83) or placebo (n = 85) was added to 0.25% bupivacaine administered extradurally for pain relief during labour. Fentanyl increased the mean duration of bupivacaine analgesia by 30% and did not reduce the rate of inadequate pain relief. Morphine did not increase the mean duration of bupivacaine analgesia significantly, but increased the rate of inadequate pain relief. It was concluded that morphine 4 mg added to extradural 0.25% bupivacaine was of no value.