Pharmacological agents affecting emesis. A review (Part II).

Part I of this article reviewed the pathophysiology of emesis, and its pharmacological treatment. Drug-induced vomiting was also discussed. In the second part of the review, other common causes of vomiting are considered. The basis of the use of antiemetics in morning sickness and migraine is still obscure; for the latter, serotonin 5-HT1 receptor agonists, 5-HT3 receptor antagonists and dopamine D2 receptor antagonists are effective. For motion sickness, control can be achieved with various antagonists of muscarinic or histamine H1-receptors. Centrally active adrenoceptor agonists in combination with a muscarinic antagonist or H1-receptor antagonist may offer better control of motion sickness and its associated symptoms than either antagonist alone; based on clinical studies, postoperative vomiting after opiate administration appears to be controlled by blocking dopamine D2, histamine H1- or muscarinic receptors. Radiation therapy appears to be similar to cytotoxic therapy in that the mediators produced or released by radiation activate both peripheral and central sites involved in the vomiting reflex. Blockade of dopamine D2 and 5-HT3 receptors may be effective.