Treating Nausea and Vomiting
Nausea and vomiting are common side effects for people undergoing cancer treatment.
Nausea is when you feel sick to your stomach and vomiting or emisis is when you empty the contents of your stomach. Both are frequently associated with chemotherapy and radiation therapy.
While significant progress has been achieved in managing chemotherapy-induced emesis over the last 25 years, nausea and vomiting continue to be the most worrying side effects of cancer chemotherapy. Due to increased use of chemotherapy in both primary and adjuvant treatment settings, it has become necessary to achieve better control of emesis in medical oncology as well as supportive care.
While a number of major oncology groups have made available consensus reports or guidelines on the potential prevention of chemotherapy-induced emesis, the introduction of newer agents can alter these paradigms. Moreover, an understanding of the neuropharmacology of this distressing problem is essential in planning patient care.
Pathophysiology of emesis
While it has still not been completely understood as to which cancer chemotherapy causes emesis, a physiologic basis for our existing understanding of this distressing problem has now become known.
Stimulation of neurotransmitter receptors
The stimulation of receptors within the CNS and/or GI tract activates the emetic reflex arc. These receptor areas pass on information to the vomiting center within the medulla, which then regulates the act of vomiting. Also located within the medulla is the chemoreceptor trigger zone (CTZ), which acts as a “chemosensor” and undergoes exposure to CSF and blood. These specific areas are home to several different types of neurotransmitter receptors.
Dopamine: In antiemetic research, the dopamine receptors remained the primary focus of interest for many years. Available antiemetics, for instance substituted benzamides (metoclopramide), phenothiazines (chlorpromazine and prochlorperazine) and butyrophenones (haloperidol and droperidol) were known to affect such receptors.
Serotonin: The function of neurotransmitter serotonin (5-hydroxy tryptamine [5-HT]) has been clearly defined. The enhanced antiemetic activity demonstrated with increased doses of metoclopramide was not explained via its dopamine-binding properties but was based on the fact that it also has an affect on serotonin receptors. These results led to the development of a number of highly specific compounds that only interact with serotonin receptors, particularly the type 3, or 5-HT3, receptor subtype. In the United States, there are 4 compounds currently available from this family – (granisetron, palonosetron [Aloxi], ondansetron, dolasetron [Anzemet]). The 5-HT3 receptor, present in both CNS and the GI tract is a key intermediary of the emetic reflex arc. New research has indicated that mutations in the 5-HT3B receptor subunit can affect antiemetic efficacy.
Substance P Tachykinins: These play a crucial role in emesis, and also in pain and several different types of inflammatory conditions. These are neurotransmitters with 11-amino acid molecules which bind to specific receptors. In case of Substance P, it binds with neurokinin type 1, or NK1, receptor.
A number of NK1 receptor antagonists have been synthetically processed and used preclinically as well as in clinical trials among cancer patients receiving chemotherapy. Results demonstrate that these agents are effective against a wide variety of factors that cause emesis, especially delayed emesis. Aprepitant (Emend), a member of this family, has received approval for clinical trials.
Cancer patients receiving chemotherapy usually experience both nausea and vomiting. In comparison to vomiting, nausea occurs more often and is more difficult to control. There exists a strong correlation between control of nausea and control of vomiting, although certain patients experience nausea without vomiting.
Described below are three of the most common emetic patters seen among patients undergoing chemotherapy:
Acute chemotherapy-induced emesis: This refers to nausea or vomiting which occurs within 24 hours of receiving chemotherapy treatment. In case of most agents, the greatest risk is between the initial 1 to 6 hours of receiving chemotherapy treatment.
Delayed emesis: This refers to emesis that occurs ≥ 24 hours after receiving chemotherapy. Delayed emesis is more likely to affect patients who receive treatment with cisplatin, cyclophosphamide, or carboplatin. New research data shows that delayed emesis can occur earlier than 24 hours in certain patients.
Anticipatory emesis: This refers to the conditioned vomiting response that occurs when adequate antiemetic protection is not used in prior courses of chemotherapy.
Emesis not related to chemotherapy
Apart from chemotherapy, there are other factors as well that can lead to emesis. For instance, emesis can develop due to concomitant medications (for example, bronchodilators, analgesics, or anti-infectives) or tumor-related complications (for example, brain metastases or intestinal obstruction). In such cases, making changes in the medication or treatment of complications related to the tumor is relatively more important than choosing an antiemetic agent.
In addition to taking antiemetics, we offer some other tips to help patients control their symptoms.
- Try eating foods and drinking beverages that have been easy for you to digest when you were sick with the flu or other conditions that would cause nausea.
- Try to avoid fatty or fried foods, very spicy foods or very sweet foods.
- Have a friend or family member make your meals for you
- Try nutritional shakes and supplements. They are packed with nutrients and are easy on your body.
- Being relaxed is an easy way to help control your symptoms. Ask your doctor about learning some simple relaxation exercises.
- Brush at least twice a day and use mouthwash to keep your mouth clean.
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