Intrathecal administration of morphine is often used for control of postoperative pain. However, pruritus is one of the most common side effects of intrathecal morphine . Specific serotonin receptor antagonists could be an effective prophylactic treatment of neuraxial opioid-induced pruritus. It was reported that palonosetron is more effective than ondansetron for prevention of postoperative nausea and vomiting. Therefore, the investigators evaluated the efficacy of prophylactic administration of ondansetron and palonosetron for the prevention of intrathecal morphine-induced pruritus.

Intrathecal administration of morphine is often used for relief of postoperative pain. However, pruritus is one of the most common side effects associated with intrathecal morphine. Specific serotonin receptor antagonists such as ondansetron could be an effective prophylactic treatment of neuraxial opioid-induced pruritus. It was reported that palonosetron is more effective than ondansetron for prevention of postoperative nausea and vomiting. Therefore, the investigators evaluated the efficacy of prophylactic administration of ondansetron and palonosetron for the prevention of intrathecal morphine-induced pruritus.

Inclusion Criteria:

• 19-70 years,
• American Society of Anesthesiology physical status 1 and 2
• Scheduled for elective urologic surgery under spinal anesthesia.

Exclusion Criteria:

• Patients with cardiac and psychological problems.
• Patients who take sedatives or narcotics.
• Patient who have allergy to study drugs.