Introduction and objectives: Postoperative complications associated with epidural use of opioids limit its wider use as an analgesic method. The purpose of this research was to describe the behavior of postoperative nausea and vomiting with the application of lyophilized morphine in epidural anesthesia. Method: Prospective, observational and single-blind study, where 3 groups, of 20 patients each, were randomly formed: Group I received preoperative medication with 10 mg of metoclopramide, Group

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... II received 4 mg of ondansetron and Group III received no preoperative medication. Results: Postoperative nausea and vomiting occurred in the sample with an incidence of 20,6 %. There were no significant differences between metoclopramide and ondansetron regarding the incidence of nausea and vomiting. These effects occurred more frequently in those patients who were mobilized in the first 12 hours in which they had oral intake during the same period of time. Conclusions: Postoperative nausea and vomiting were relatively frequent side effects as a result of applying lyophilized morphine to the epidural anesthesia. Metoclopramide was as effective as ondansetron in its antiemetic effect. Nausea and vomiting were more common in patients who were mobilized and had oral intake in the first 12 hours, and in those who received no antiemetic premedication.