Abstract:Objective: To evaluate the effects of prophylactic intravenous administration of the 5-hydroxytryptamine subtype 3(5-HT3) receptors antagonist azasetron on intrathecal morphine-induced pruritus.Methods: 150 patients were randomized into group A1(n=50,azasetron 10 mg,IV),group A2(n=50,azasetron 20 mg,IV) and group C(n=50,normal saline 4 ml).The spinal anesthesia were proceeded with 2.5 ml of 0.5% hyperbaric bupivacaine containing 0.4 mg of morphine in patients with the lower abdomen and the lower limbs surgery. The incidence and severity of pruritus were evaluated at 2,4,8,12,24,36,48 h after intrathecal morphine injection.Results: The incidence and severity of pruritus were significantly lower in group A1 and group A2 than group C(62%,48%,and 82% respectively,P<0.05).Time of occurrence and duration of pruritus were similar in three groups.Conclusion: The prophylactic use of azasetron helps to reduce the incidence and severity of intrathecal morphine-induced pruritus.