Comparison of Ondansetron with Gabapentin for prevention of intrathecal morphine induced pruritus

Background:Ondansetron has been used successfully for prophylaxisand treatment of intrathecal morphine induced pruritus.Gabapentin has anxiolytic, antiemetic, antipruritic effectsand has also been shown to potentiate the analgesiceffect of intrathecally or epidurally administered opioids. Materials and method: We compared the effectiveness oforal gabapentin with intravenous ondansetron to preventincidence of intrathecal morphine induced pruritus. In aprospective, double-blind study, sixty patients aged 18-65years with ASA physical status I and II undergoing surgeryunder subarachnoid block were randomized to receiveplacebo tablets (ondansetron group) or gabapentin 1200mg (gabapentin group) 2 hours before surgery. Patientsreceiving placebo tablets received 8 mg of intravenousondansetron and those receiving gabapentin received 4ml of intravenous normal saline just prior to subarachnoidblock with 3 ml of 0.5% hyperbaric bupivacaine plus 0.2mg morphine. The incidence, onset, severity, location ofpruritus and incidence of side effects were studied for next24 hours. Results The overall incidence of pruritus was48.3%. The incidence, severity, location of pruritus wascomparable between the two groups. There was significantdifference between the onset of pruritus between groups(p=0.009). The incidence and grade of nausea vomiting,requirement of intraoperative sedation was comparablebetween groups. The incidence of urinary retentionwas significantly high in gabapentin group (p=0.020).Respiratory depression was observed in one patient. Conclusion: A single dose of 1200 mg oral gabapentin 2hours before, is as effective as prophylactic intravenousondansetron 8 mg for prevention of intrathecal morphineinduced pruritus.