Szarvas et al in their prospective, double-blinded rand- omized study found out that failure of PONV prophy- laxis in the 24 hour postoperative period occurred more frequently in patients who received dexamethasone alone (29 of 40; 73%) compared with those who received a combination of dexamethasone and ondansetron(19 of 43; 44), P 0.01. Dexamethasone is thought to have
a late onset antiemetic effect which might have contrib- uted to its higher incidence of nausea and vomiting in this study. All the patients who had nausea or vomiting actually experienced them early (0-4hours). Therefore, in this study and in a previous study by Wang et al dexamethasone could be said to be ineffective against early PONV