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Ondansetron for prevention of intrathecal opioids-induced pruritus, nausea and vomiting after cesarean delivery.

We have read with interest the article by Charuluxananan et al. (1) that compares the effectiveness of nalbuphine and ondansetron in the prevention of intrathecal morphine-induced pruritus after cesarean delivery. The authors found that prophylactic nalbuphine and ondansetron were both effective in reducing pruritus but not nausea and vomiting induced by 0.2 mg of intrathecal morphine. In a similar study (2), we assessed the efficacy of ondansetron for the prevention of pruritus, nausea, and vomiting induced by intrathecal sufentanil-morphine in 100 patients undergoing cesarean delivery. Doses of drugs used were 8 mg of ondansetron, 0.1 mg of morphine, and 2.5 g of sufentanil. The incidence of nausea and vomiting, in this study, was significantly reduced in the treatment group when compared with the placebo group (18% vs 48%; P 0.001). However, the incidence of pruritus was not decreased in the treatment group when compared with the placebo group (76% versus 82%; P 0.46). These results are not in agreement with the data reported by Charuluxananan et al. Failure of ondansetron to prevent pruritus in our study may be explained by the fact that sufentanil—which is a highly lipophilic opioid with a quick onset of action—was added to intrathecal morphine. The serotonin receptors in the spinal cord were probably activated by sufentanil before they were blocked by ondansetron. Furthermore, and because the incidence of nausea and vomiting following intrathecal opioids is dosedependent (3), the effectiveness of ondansetron in our study could be related to the low dose (0.1 mg) of the intrathecally administrated morphine as compared with the higher dose (0.2 mg) used by Charuluxananan et al. In conclusion, prophylactic ondansetron decreases the incidence of intrathecal opioid-induced pruritus, nausea, and vomiting after cesarean delivery. However, ondansetron may not be effective when highly lipophilic opioids or increased doses of morphine are administrated.