Seven double-blind RCTs studied intravenous and oral administration of ondansetron for the treatment of PONV (1,623 patients).
Twenty double-blind RCTs studied intravenous and oral administration of ondansetron for the prevention of PONV (4,364 patients).
Methodological flaws in the primary studies included the following: failure to indicate the nausea/vomiting rating scale or method of data collection; potential lack of sensitivity of dichotomous scales for nausea and vomiting; lack of stratification for identified PONV risk factors; failure to use recommended ondansetron dose; collection of data after only four hours; and small sample size.
The majority of patients in the published reported were women.
Prevention of post-operative nausea and vomiting:
1. Prophylactic oral pre-medication with a single dose (one RCT with 150 patients. Validity score 4): incidence of nausea or emetic symptoms was significantly fewer in ondansetron group compared to placebo (13 patients vs 25 patients reporting symptoms; P < 0.05).
2. Prophylactic oral pre-medication with additional post-operative doses (two multicentre RCTs with 393 patients. Validity scores 5 and 4): significantly lower incidence of both nausea and vomiting in ondansetron group compared to placebo reported in both trials (P < 0.005, and P < 0.001).
3. Prophylactic single dose given at induction (14 RCTs, number of patients was not stated): three early studies did not use the dose of ondansetron recommended by the manufacturer. Seven RCTs reported efficacy rates of ondansetron in preventing serious emetic sequelae ranging from 72% to 94%.
Treatment of post-operative nausea and vomiting:
1. Treatment of PONV in patients receiving regional anaesthesia (one RCT with anti-emetic therapy of 1mg, 4 mg, and 16 mg ondansetron or placebo given on patients' request, number of patients was not stated. Validity score 5): 4mg and 16 mg doses of ondansetron were more effective than placebo for the control of opioid induced emesis (P < 0.005). 2. Treatment of PONV in women undergoing gynaecological procedures (four RCTs with 1495 patients): One RCT (175 women. Validity score 5) reported that freedom from emetic sequelae over 24 hours was significantly higher in the group that received 4 mg ondansetron compared to 10 mg metoclopramide or placebo (55.2% vs 29.8% vs 11.7%; P < 0.001). One RCT (846 patients. Validity score 3) reported that freedom from further nausea was greater in 4 mg ondansetron group compared to 10 mg metoclopramide (59% vs 41%) with ondansetron receiving higher patient satisfaction scores (P < 0.001).
One RCT (74 women. Validity score 4) compared ondansetron, alizapride, and droperidol and found no statistically significant difference after four hours. One RCT (400 patients. Validity score 4) showed all three ondansetron doses (1, 4 and 8 mg) were significantly better than placebo in treating PONV and preventing its recurrence (P < 0.001).
3. Treatment of PONV: other studies. One RCT found 8 mg ondansetron to be significantly more effective than placebo in preventing further emetic episodes (P > 0.01).