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The use of opioids for postoperative analgesia may be limited by side effects such as nausea and vomiting. Because ondansetron, a selective serotonin type 3 (5-hydroxytryptamine [5-HT3]) antagonist, is effective for chemotherapy and general anesthesia-induced nausea and vomiting, we hypothesized that it may also be effective for opioid-induced nausea and vomiting. ASA physical status I-III patients undergoing regional anesthesia were eligible for the study. Those who requested an antiemetic after postsurgical opioid administration were randomized to receive a single dose of ondansetron (0.1 mg, 4 mg, or 16 mg intravenously [I.V.]) or placebo in a double-blind fashion. Emetic episodes, nausea and pain ratings, and adverse events were recorded for 24 h after study drug administration. Patient satisfaction scores were obtained 24 h after study drug infusion. A significantly (P < 0.05) larger proportion of patients treated with ondansetron 4 mg and 16 mg experienced no emetic episodes, received no rescue antiemetic, and completed the study compared with placebo. Nausea scores and patient satisfaction scores in the ondansetron 16-mg group were significantly (P < 0.05) more favorable than in the placebo group. Postsurgical pain scores did not differ among groups. The incidence of adverse events was similarly low across groups. The results of this study support our hypothesis that I.V. ondansetron is effective for postsurgical opioid-induced nausea and vomiting.

Summary Use of α2-adrenergic agonists represents an exciting new vista in the anaesthetist's pharmacological armamentarium. Further work with the α-agonist dexmedetomidine, may open the way to take advantage of this very potent, α-specific compound. Many studies, currently ongoing, should help guide us to the proper use of these compounds. A recent international symposium, ‘α2-Adrenergic Mechanisms of Spinal Anesthesia', attests to the broad and global interest concerning α2-adrenergic agonists (Eisenach et al, 1993). Clearly, further well controlled studies examining outcome variables are needed to help gauge the true clinical worth of α2-adrenergic agonists.