Many patients getting chemotherapy worry about nausea and vomiting more than any other side effects. Doctors know which drugs are most likely to cause nausea and vomiting during cancer treatment, and they make plans based on which drugs you are getting. The goal is to prevent vomiting entirely.
Many medicines are available to help prevent or treat nausea and vomiting, making it less common than in the past, but it can still happen.
Chemotherapy drugs cause nausea and vomiting for a variety of reasons. One reason is they irritate the lining of the stomach and duodenum (the first section of the small intestine). This stimulates certain nerves that activate the vomiting center (VC) and the chemoreceptor trigger zone (CTZ) in the brain which leads to vomiting. Another way these areas of the brain can be activated is through obstruction (intestinal blockage), slowed stomach emptying, or inflammation — all possible effects of chemotherapy.
Nausea is an unpleasant wavelike sensation in the stomach and back of throat. It can be accompanied by symptoms like sweating, light-headedness, dizziness, increased salivation, and weakness. It can lead to retching, vomiting, or both.
Retching is a rhythmic movement of the diaphragm and stomach muscles that are controlled by the vomiting center.
Vomiting is a process controlled by the vomiting center that causes the contents of the stomach to be forced out through the mouth. Vomiting can happen right after chemotherapy, or later. If it happens within minutes to hours after chemotherapy, it is called acute vomiting. If it develops or continues for 24 hours or more after chemotherapy, it is called delayed vomiting or delayed emesis. This type sometimes lasts for days.
Anticipatory nausea and vomiting can happen when you have had a bad experience with nausea and vomiting in the past. This conditioned response can be stimulated by sights, sounds, or odors. As a result, you develop nausea and sometimes vomit when placed in the same situation (for example, before receiving the next chemotherapy treatment). There are some types of treatment that may help this after it has started, but prevention is best.
The key to effective control of nausea and vomiting is to prevent it before it occurs whenever possible. For this reason, medicines for nausea and vomiting are started before the chemotherapy is given. Many drugs are used alone or in combination to prevent or control nausea and vomiting. Drugs used in this way are called anti-emetics.
Although it is not possible to predict the onset, severity, or duration of nausea and vomiting for any one person, certain chemotherapy drugs are more likely to cause nausea and vomiting.
Different cancer drugs have different risks of nausea and vomiting
Nearly any drug can cause nausea in a few people. But some cancer treatment drugs cause nearly everyone who takes them to become nauseated or vomit. Other cancer drugs cause less nausea. Cancer doctors classify cancer drugs by the chance that they will cause vomiting into high, moderate, and low vomiting risk drugs.
Doctors can use this information about the vomiting risk of a drug to help them better prevent vomiting. For instance, they might give extra anti-emetic drugs before they give a cancer drug with higher vomiting risk. A person getting a high-risk drug may be given 2 or more anti-emetic drugs before the cancer treatment. During and after the chemo, nausea may be managed by giving anti-emetic medicine on a set schedule, with an extra drug for vomiting that happens despite the anti-emetic treatments (breakthrough vomiting). In contrast, a person getting a drug with very low vomiting risk may only need an anti-emetic drug if they have nausea after they get the cancer drug.
You can find more information on which drugs cause more vomiting and the kinds of anti-emetic medicines doctors can use in our document called Nausea and Vomiting.
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