Ondansetron and tropisetron do not prevent intraspinal morphine- and fentanyl-induced pruritus in elective cesarean delivery.

Department of Anaesthesia and Intensive Care, Helsinki University Central Hospital, Helsinki, FinlandBackground: Although intraspinal morphine has been shown tobe effective in providing analgesia after cesarean delivery, prur-itus as a side-effect remains a common cause of dissatisfaction.The role of ondansetron has been studied in preventing pruritusbut the results have been contradictory.Methods: We randomized 98 parturients undergoing electivecesarean section using combined spinal-epidural anesthesiainto a double-blinded trial to receive tropisetron 5 mg (Tgroup) or ondansetron 8 mg (O group) or placebo (NaClgroup) after delivery, when intrathecal morphine 160 mg andfentanyl 15 mg were used for post-operative pain control. Thepatients additionally received ketoprofen 300 mg per day. Post-operative itching, nausea and vomiting, sedation and need forrescue analgesics were registered every 3 h up to 24 h, and allpatients were interviewed on the first post-operative day.Results: Seventy-six percent of the parturients in the placebogroup, 87% in the ondansetron, and 79% in the tropisetrongroup had itching. The incidence of post-operative nausea andvomiting was 21%, 20% and 11% of the patients in the placebo,ondansetron and tropisetron groups, respectively. Medicationfor pruritus was needed by 31%, 23% and 39% of the patientsin the placebo, ondansetron and tropisetron groups, respec-tively. In the post-operative questionnaire, the patients reportedless post-operative nausea in the tropisetron group than in theplacebo group (P < 0.01).Conclusion: Neither ondansetron nor tropisetron prevent itch-ing caused by intrathecal morphine with fentanyl. However,tropisetron reduced post-operative nausea.