Nausea and vomiting, among the most distressing symptoms the patient may have to endure, may at the same time seriously interfere with his proper management. Considerable evidence indicates that there are two components to the central nervous system physiology of this symptom complex. First, emetic substances introduced into the body and circulating in the blood may cause nausea and vomiting either by activating the chemoreceptor trigger zone in the floor of the fourth ventricle or by acting directly on the nearby emetic center. Second, abnormal labyrinth or extracranial activity may set up nerve reflexes which activate the emetic center.1 The control of nausea and vomiting, therefore, depends ultimately on suppression of activity of the emetic center or of the chemoreceptor trigger zone.
Chlorpromazine, a widely used and potent antiemetic of the phenothiazine series, exerts a minor depressant action on the emetic center.2 It also provides an excellent means