The objective was to compare analgesic effect of combined epidural morphine-midazolam with either drug alone on postoperative pain in patients undergoing major abdominal cancer surgery.

Eighty-four patients were allocated in prospective randomized double-blind study to receive epidural analgesia. Patients received 5 mg morphine in morphine (Mor) group, 5 mg midazolam in midazolam (Mid) group, 5 mg morphine + 5 mg midazolam in morphine-midazolam (MM) group, 0.25% bupivacaine was added to injected solution with same volume in all groups. All groups were compared with time of first analgesic request, total analgesic consumption, number of epidural doses, postoperative Visual Analog Scale score, and adverse events.

Time of first analgesic request was 4 to 8 hours in Mid versus 12 to 23 and 14 to 24 hours in Mor and MM groups, respectively, with significant difference between Mid versus Mor (P<0.001), Mid versus MM (P<0.001), and Mor versus MM groups (P<0.031). Analgesic consumption was more in Mid than Mor and MM groups, with significant difference between Mid versus Mor (P<0.008), Mid versus MM (P<0.001), with no significant difference between Mor and MM groups (P<0.6). The number of epidural doses in Mid was 1 to 3 versus 1 to 3, and 1 to 2 in Mor and MM groups, respectively, with significant difference between Mid versus Mor (P<0.025), Mid versus MM (P<0.004), with no significant difference between Mor and MM groups (P=1.0).

Addition of midazolam to epidural morphine prolonged time of first analgesic request and decreased total analgesic consumption.