Although oral rehydration is generally regarded as best treatment for children with gastroenteritis, intravenous rehydration may be resorted to when the child vomits repeatedly. Antiemetics have been used but evidence of their value is limited. Researchers in Chicago ( Stephen B Freedman and colleagues. New England Journal of Medicine 2006;354:1698–705OpenUrlCrossRefPubMedWeb of Science) have used oral ondansetron (a serotonin₃ (5H T₃) agonist).

The trial took place in a children’s emergency department in 2004–5 …