Drug treatment of chemotherapy-induced delayed emesis.

Chemotherapy-induced emesis has a major adverse impact on patients undergoing therapy for various malignancies, and this has led to considerable research in this field. Most investigative efforts have concentrated on the acute phase of emesis that occurs within the first 24 hours after chemotherapy, and significant strides forward have been made with this problem. Better control of acute emesis with newer agents such as the serotonin 5-HT3 receptor antagonists has focused increasing attention on a second phase of nausea and vomiting, known as delayed emesis, which occurs more than 24 hours after chemotherapy. This delayed phase is often not as well controlled with the antiemetics that have proven effective in acute emesis, and contributes to the distress associated with emetogenic chemotherapy. Most of the available data on delayed emesis are based on studies with cisplatin-based regimens, with much less understanding of delayed nausea and vomiting induced by non-cisplatin-based chemotherapy. Nevertheless, it is evident that the patterns of delayed emesis associated with cisplatin and non-cisplatin chemotherapy have distinct differences. The control of delayed emesis, especially following cisplatin, remains a therapeutic challenge. Contributing to the lack of progress has been the absence of an experimental model to help in elucidating the pathophysiology of delayed emesis and in the evaluation of new therapeutic approaches. The combination of metoclopramide and dexamethasone, although superior to placebo in randomised trials, provides only moderate control of delayed emesis following high-dose cisplatin. The 5-HT3 receptor antagonists that are effective in the prevention of acute emesis with cisplatin have failed to make a major impact on the delayed phase. When combined with dexamethasone, these agents provide no additional benefit to that achieved using dexamethasone alone or dexamethasone combined with metoclopramide. With non-cisplatin chemotherapy, corticosteroids and 5-HT3 receptor antagonists are the most useful agents. Efforts are ongoing to identify more effective treatments for delayed emesis. One novel approach involves the blockade of substance P binding to neurokinin-1 (NK1) receptors. This article reviews what is currently known about chemotherapy-induced delayed emesis, with a focus on treatment strategies.