Comparison of metoclopramide and ondansetron for the prevention of nausea and vomiting after intrathecal morphine.

Nausea and vomiting remain unpleasant side effects of intrathecal (i.t.) morphine and of the numerous therapies tried, only prophylactic intravenous (i.v.) metoclopramide has been reported to be promising. Seventy-three patients, scheduled for orthopaedic prosthesis surgery of the hip or knee were studied. They received 4 mL of plain bupivacaine and 0.3 mg of preservative-free morphine i.t. for anaesthesia. The test drugs given in a double-blind and randomized fashion, were either metoclopramide 20 mg, three times, at 6 h intervals (23 patients), ondansetron, 8 mg, twice, at 12 h intervals (25 patients), or 0.9% saline three times, at 6 h intervals (25 patients). The occurrence of nausea, vomiting and pain was followed for 24 h. The incidences of nausea and vomiting were 60% (15/25) and 56% (14/25) in the saline group, 52% (12/23) and 48% (11/23) in the metoclopramide group, and 52% (13/25) and 40% (10/25) in the ondansetron group. Incidences of severe vomiting were 24, 35 and 12% respectively. Eight patients in the saline group, seven in the metoclopramide and 10 in the ondansetron group did not need additional opioids for post-operative pain relief. We conclude that, metoclopramide and ondansetron were not better than saline in the prevention of post-operative emesis induced by intrathecal morphine.