The use of 5-HT 3 antagonists in the prevention and treatment of postoperative nausea and vomiting in children has also been studied. The ondansetron-treated patients also had an overall shorter length of hospitalization. Unlike other antiemetics, such as benzodiazepines or phenothiazines, the 5-HT 3 antagonists are relatively free of adverse effects. For example, extrapyramidal symptoms are much less likely to occur with the selective 5-HT 3 antagonists than with antiemetics which also bind to dopamine D 2 receptors, such as metoclopramide. Specificity for 5-HT 3 receptors, however, is greater with granisetron than ondansetron.
Constipation occurs approximately twice as often as diarrhea in patients treated with granisetron.
Ondansetron causes these effects in nearly equal numbers. In pediatric trials, adverse effects appear relatively rare, with most reporting only sedation and mild headache. At this time, there have been no significant drug interactions documented with the 5-HT 3 antagonists. However, these reactions do not appear to be clinically significant and there are no recommendations for dosage adjustment based on drug interactions. Intravenous ondansetron should be given over 15 minutes.