Chemotherapy induces vomiting by:
A. Stimulating neuroreceptors in the medulla.
B. Inhibiting the release of catecholamines.
C. Autonomic instability.
D. Irritating the gastric mucosa.
Correct Answer: A. Stimulating neuroreceptors in the medulla.
Vomiting (emesis) is initiated by a nucleus of cells located in the medulla called the vomiting center. This center coordinates a complex series of events involving pharyngeal, gastrointestinal, and abdominal wall contractions that lead to the expulsion of gastric contents.
Option B: Catecholamine inhibition does not induce vomiting. First, catecholamines have been shown to have a growth-promoting effect on tumor cells. In addition, catecholamines have been shown to have an anti-apoptotic effect on cancer cells and may render tumor cells resistant to chemotherapeutic drugs.
Option C: Chemotherapy does not induce vomiting from autonomic instability. While some chemotherapy drugs may cause neuropathy, others do not. Even with the drugs known potentially to be toxic to nerves, only about 30 percent of patients who receive them will develop peripheral neuropathy due to treatment. Risk of developing neuropathy, however, is one of the main reasons for limiting the amount of chemotherapy a person is given. Peripheral neuropathy that leads to numbness, tingling, and pain in the hands and feet is much more commonly associated with chemotherapy medications than autonomic neuropathy. When peripheral neuropathy develops as a result of chemotherapy, symptoms typically fade away within several months of the end of treatment. But it can sometimes take longer than that.
Option D: Chemotherapy, especially oral agents, may have an irritating effect on the gastric mucosa, which could result in afferent messages to the solitary tract nucleus, but these pathways do not project to the vomiting center. Mucous membranes line many of the organs in the body, from the mouth to the rectum and vagina. Chemotherapy can damage cells in the mucous membrane so they become inflamed (a condition called mucositis). This can lead to painful ulcers, bleeding and infection. Mucositis is usually temporary and goes away a few weeks after treatment.