Antiemetic effect of ondansetron 0.2 mg mL−1 in PCA morphine solution

BACKGROUND AND OBJECTIVES: To study the effect of 0.2 mg mL-1 of ondansetron added to morphine patient-controlled analgesia solution after a 4 mg loading dose on the incidence and severity of postoperative nausea and vomiting. METHODS: One hundred and sixty patients scheduled for elective surgery, between 18 and 65 yr old, were studied. Patients who smoked, received antiemetics and hormonal therapy, had a history of motion sickness or gastrointestinal disease, a body mass index >35 or menstruation at the time of the study were excluded. Patients were assigned to the ondansetron and control groups by block randomization. At the end of anaesthesia, all patients received 4 mg of ondansetron intravenously and the same patient-controlled analgesia regimen of morphine. The ondansetron group (n = 80) received 0.2 mg of ondansetron per 1 mg of morphine. The nausea score, vomiting score and the requested ondansetron dose were evaluated at 1, 2, 6, 12 and 24 h. Patient-satisfaction for nausea/vomiting was recorded at the end of the study. RESULTS: Patient characteristics and cumulative morphine consumption were similar but ondansetron group had higher pain scores (P = 0.006). The ondansetron group had a lower nausea and vomiting scores, and more patients were free from nausea and vomiting than the control group (41 vs. 26, respectively, P = 0.025). The ondansetron group had fewer cumulative ondansetron doses than the control group and better patient satisfaction than the control group (P < 0.05). CONCLUSION(S): Ondansetron 4 mg plus 0.2 mg mL-1 given with PCA morphine can reduce nausea and vomiting thus improving patient satisfaction.