The vomiting patient

The causes of vomiting can be grouped into two categories, corresponding to the neural sites of emetogenesis--the emesis center (EC) and the chemoreceptor trigger zone (CTZ). Anatomic disorders induce vomiting via the EC, whereas toxic and metabolic problems do so via activity of the CTZ. Antihistamines have antiemetic effects at the EC; phenothiazines and related compounds block vomiting mediated by the CTZ. Thus, a pharmacologic approach to this problem can be logically constructed.