The primary objectives of this study are to compare the efficacy of pain relief between epidural oxycodone and epidural morphine for postoperative analgesia after elective caesarean section and to compare the incidence and severity of pruritus. Secondary objectives are to compare other side effects of epidural administered oxycodone and morphine (nausea and vomiting, sedation, respiratory depression) and to investigate the safety and efficacy of epidural oxycodone and epidural morphine after use for postoperative analgesia in caesarean sections.

Undesirable side effects such as pruritus and nausea are common with epidural morphine and are thought to be due to mu-opioid receptor stimulation at the supra-spinal level. Recent studies of epidural oxycodone for abdominal and gynaecological surgery have shown that it is as effective as morphine with fewer side effects by this route. This has not been established in patients undergoing caesarean section. Oxycodone is a semi-synthetic opioid derivative that resembles morphine structurally and has similar lipid solubility. It has been reported that the analgesic action of oxycodone is more rapid in onset when compared with morphine and is mediated by kappa-opioid receptors in the spinal cord. The significance of our study would be to establish that epidural oxycodone reduces the side effects of pruritus of epidural morphine whilst still maintaining similar analgesia.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) physical status 1-2,
• aged between 21 to 50 years undergoing a term elective caesarean section and
• had consented for combined spinal-epidural (CSE) anaesthesia

Exclusion Criteria:

• concurrent opioid therapy,
• contraindications to CSE anaesthesia or any of the study medications,
• a history of pre-existing nausea and vomiting,
• failure to identify intrathecal space at time of anaesthesia,
• inadvertent dural puncture with the epidural needle and
• conversion of regional anaesthesia to general anaesthesia