New Vistas in the Pathophysiology of Vomiting

Abstract

Copyright: © 2013 Darmani NA. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Vomiting (emesis) is currently viewed as a complex multi-transmitter protective reflex mechanism which has developed in diverse species to different degrees to remove toxic agents from the gastrointestinal tract prior to their absorption. Not all animals are capable of vomiting and despite extensive research, the reflex is only partially characterized [1]. Nausea is an unpleasant sensation of gastrointestinal discomfort and may accompany or precede vomiting (a forceful expulsion of gastrointestinal contents). However, both events can be experienced separately and remain a significant clinical problem. Although several animal models of emesis are available in the laboratory, only few such models exist for the study of nausea. Thus, our knowledge of nausea, its related brain-gut circuit(s), associated neurotransmitters, and pathophysiology is even more limited with no noteworthy anti-nausea agent available in the clinic. In fact the severity of chemotherapy-induced vomiting can be controlled to a significant extent by combined antiemetic regimens, but control of nausea still remains a persistent problem. Retching is rhythmically alternating abdomino-thoracic contractions (with the glottis closed), and is also associated with emesis. Nausea, retching and vomiting are hallmarks of several gastrointestinal disorders including gastroenteritis, anorexia nervosa, bulimia, hyperemesis gravidarum, and cyclic vomiting syndrome. Conditions such as pregnancy, motion, space sickness, and surgery are also accompanied by nausea, retching and vomiting. Likewise, vomiting and associated behaviours can develop as a specific response to treatments such as radiation or chemotherapy, or appear as side effect of numerous clinically used drugs such as antidepressants, opiates, cholineesterase inhibitors, L-DOPA, phosphodiesterase inhibitors, and cardiac glycosides. In addition, vomiting can be a response generated by cognitive, visual, flavour or CNS disorders including anxiety and stress. Prolonged emesis induces severe dehydration, electrolyte imbalance and even death which are features for human rotavirus disease as well as cholera and staphylococcal food-borne infections. The current literature identifies no specific antiemetic that works for all types of vomiting, or in all patients suffering from a specific type of emesis. Thus, treatment tends to be based on individual clinicians’ experience and time after time combination antiemetic regimens are needed to manage patients successfully. Even with combination regimens certain kinds of emesis such as chemotherapyinduced nausea and vomiting (CINV) can only be completely controlled in 70-80% of cancer patients receiving chemotherapy.