Chemotherapy-Induced Nausea and Vomiting (CINV)
When chemotherapy enters the body, sensors in the digestive system and brain detect its presence as a foreign substance. In a complex series of signals among the brain and the mouth, stomach, small intestine and bloodstream, the medication stimulates the “vomiting center” in the brain. Several chemicals, including ones called serotonin and substance P, are released, triggering the nausea and vomiting reflex. This is the body’s effort to get rid of the foreign substance.
Some people experience nausea and vomiting side effects from chemotherapy within the first few hours of receiving chemotherapy. Doctors call this reaction “acute nausea and vomiting.” Other patients don’t feel symptoms the day of chemotherapy but may develop nausea and vomiting during the next few days. This condition is called “delayed nausea and vomiting.”
You shouldn’t assume that nausea and vomiting that occurs a day or two after treatment isn’t related to chemotherapy. It’s important to tell your doctor or nurse when you experience these symptoms, no matter when they occur.
Because some people getting chemotherapy expect to feel ill, they may start experiencing symptoms even before their treatment begins. This is referred to as “anticipatory nausea and vomiting.” Sometimes, the sights, sounds or smells of the treatment room can trigger this reaction.
There are anti-nausea medications that your doctor will decide to prescribe based on the type of chemotherapy you are getting and how much nausea and vomiting might be expected. Sometimes, patients receive anti-nausea drugs intravenously (through a needle inserted into a vein). Other anti-nausea medications are available in pill or liquid form to take by mouth, as a skin patch or as a suppository (a soft cone- or cylinder-shaped capsule containing medication that dissolves in the rectum).
After chemotherapy, you may also be given anti-nausea medications to take at home. It’s important to understand how these drugs should be taken. To prevent CINV, some medications are designed to be taken for several days, whether you feel nauseous or not. Others are meant to be taken only when you feel nauseous. If you have questions about when you should take your anti-nausea medication, be sure to call your doctor or nurse.
It is vital that you have a clear understanding of the order in which you take your medications—both chemotherapy (whether intravenously or by mouth) and anti-nausea drugs— as well as the times at which you take them.
If you are taking the medications as directed and you continue to have CINV, contact your doctor right away. It’s very important to stay hydrated (keep fluids in your system) so that the body’s salts, or electrolytes, stay in balance and the cells can work properly. See “Coping With Nausea and Vomiting” on the right side of this page for tips on staying hydrated.
Generally, anti-nausea drugs fall into the following categories:
Corticosteroids. Corticosteroids, which are related to the natural hormone cortisol, are widely used to help prevent nausea and vomiting caused by chemotherapy. They have been successfully used for many years, especially to prevent delayed nausea and vomiting. Corticosteroids such as dexamethasone (Decadron, Hexadrol and others) can be given in different forms and are often combined with other anti-nausea drugs for maximum benefit.
Serotonin antagonists. Serotonin antagonists are often used to counter nausea and vomiting resulting from powerful chemotherapy drugs such as cisplatin (Platinol and others) and cyclophosphamide (Cytoxan, Neosar and others). Serotonin antagonists stop serotonin (a substance occurring naturally in the brain) from sending a signal that causes vomiting. These drugs are usually administered intravenously before chemotherapy begins.
One of these drugs, palonosetron (Aloxi), continues to work for days after a single injection. It can prevent both acute and delayed nausea and vomiting. Other serotonin antagonists include ondansetron (Zofran and others), granisetron (Kytril), and dolasetron (Anzemet). Like palonosetron, dolasetron is given as an injection. Ondansetron is given in tablet or liquid form, and granisetron is given either via an injection or in tablet form.
Dopamine antagonists. Metoclopramide and prochlorperazine are two commonly used medicines in this class of drugs. They are often prescribed for “breakthrough” nausea and vomiting—that is, symptoms not already controlled with other types of medications.
NK-1 inhibitors. Aprepitant (Emend) works on the vomiting center of the brain to prevent nausea and vomiting caused by chemotherapy. It blocks the action of substance P, a peptide that triggers nausea and vomiting reflexes. Aprepitant is sometimes given in combination with corticosteroids and serotonin antagonists. It is available as a capsule, and is taken before a chemotherapy session and for two days afterward.
Cannabinoids. These medications contain a purified form of the active ingredient found in marijuana. For a number of years, doctors have prescribed dronabinol tablets as an anti-vomiting drug. In 2006, the U.S. Food and Drug Administration approved nabilone (Cesamet) tablets, which can control CINV in cancer patients who have not been adequately helped by other anti-nausea medications. Like marijuana, dronabinol and nabilone can cause sedation (relaxation or sleepiness) and mood changes. Read CancerCare’s fact sheet titled, “Medical Marijuana and Cancer” for more information.
Anti-anxiety drugs. Medications such as lorazepam (Ativan and others) or diazepam (Valium and others) are used to help block nausea and vomiting. These sedatives (from the benzodiazepine family of medications) can be given intravenously and in pill form. To avoid becoming dependent on such medications, a careful schedule should be worked out with your doctor or nurse. They can also effectively relieve the anxiety that people can feel when they believe they’re about to experience these symptoms.