Comparison of epidural methadone with epidural diamorphine for analgesia following caesarean section

Analgesia provided by either 5 mg diamorphine, or 5 mg methadone administered by the epidural route during elective caesarean section was compared in 40 women. The median time to further analgesia in the methadone group was 395 min, and 720 min in the diamorphine group, P = 0.0003. Linear analogue scores to assess pain were measured 2-hourly for 12 h, then again at 24 h postoperatively. Pain scores were significantly lower in the diamorphine group at 8 and 10 h. The median cumulative i.m. morphine dose administered during the first 24 h was 20 mg in the methadone group and 0 mg in the diamorphine group (P = 0.0005). Nausea and pruritus were common side effects in both groups. Continuous pulse oximetry data were available for 12 h post-operatively in 15 patients receiving methadone, and in 17 patients receiving diamorphine. One or more episodes of significant desaturation (< 90% for 30 s), occurred in three patients receiving methadone, and in nine patients receiving diamorphine. Desaturation to 90-92% occurred in a further three patients given epidural diamorphine, and in one further patient given epidural methadone.