How anti-emetic drugs work

The management of nausea and vomiting in the central nervous system is particularly important in cancer chemotherapy and palliative care. This chapter describes the actions of anti-emetic drugs in the central nervous system and gut. The most powerful anti-emetics, granisetron, ondansetron and palonosetron, are selective 5-HT₃ antagonists. The antipsychotic drugs, the phenothiazines are useful anti-emetics, as antagonists of the dopamine D₂ receptors in the chemoreceptor trigger zone. Metoclopramide and domperidone are both dopamine D₂ receptor antagonists acting in the chemoreceptor trigger zone. Metoclopramide has the advantage of also being 'prokinetic', that is it is a specific stimulant of the 5-HT₄ receptors in the gastro-intestinal tract which promote peristalsis. The much older histamine H₁ receptor antagonists block H₁ receptors peripherally, as well as in the central nervous system.