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 CINV 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 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.
Treating Nausea and Vomiting
Drug companies have been developing anti-nausea medications for the past 40 years. Your doctor will decide which drugs 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 antinausea 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. Related to the natural hormone cortisol, corticosteroids are widely used to help prevent CINV. They have been used successfully for many years, especially to prevent delayed nausea and vomiting. Corticosteroids such as dexamethasone may be given in many different forms and are often combined with other anti-nausea medications for the most benefit.
Serotonin antagonists. This type of medication blocks natural substances from sending a signal to the brain that causes vomiting. Palonosetron (Aloxi) continues to work for days after a single injection. It can prevent both acute and delayed nausea and vomiting. Other serotonin antagonists available in the United States include ondansetron (Zofran and others), granisetron and dolasetron (Anzemet), which can all be given as a pill or injection. Ondansetron and granisetron are both available in liquid form, and ondansetron also comes in a tablet that dissolves in the mouth. These forms of medication are especially helpful for people who have trouble swallowing pills or keeping them down when they are feeling nauseous.
Dopamine antagonists. Metoclopramide (Reglan and others) 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. This is the newest class of medicines to prevent CINV. Aprepitant (Emend and others) is used when patients receive chemotherapy that is very likely to cause acute or delayed nausea and vomiting. Available as a capsule, aprepitant is taken before a chemotherapy session and for two days afterward. A related drug, fosaprepitant dimeglumine (Emend for Injection), is delivered intravenously and converted to aprepitant in the body.
Cannabinoids. These medications contain a purified form of the active ingredient found in marijuana. For a number of years, doctors have prescribed dronabinol (Marinol and others) 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.
Motion sickness treatments. Like cannabinoids, these types of medication are helpful in reducing any nausea or vomiting that lingers more than a few days after chemotherapy. Scopolamine (Transderm Scop) comes as a patch to be placed on the skin behind the ear. Although scopolamine was not originally intended for people on chemotherapy, it can be used to treat CINV.
Anti-anxiety drugs. Medications such as lorazepam (Ativan and others) are used to sedate patients and to help block nausea and vomiting. Sedatives 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.
Stomach acid blockers. Known as proton pump inhibitors and histamine H2-receptor antagonists, these medications block the formation of stomach acid. This reduces indigestion and heartburn, which can sometimes lead to nausea and vomiting. All of these drugs can be bought without a prescription, and they are often available in less-expensive, generic forms. Be sure to talk with your doctor first before using over-thecounter drugs. Examples of these drugs include omeprazole (Prilosec and others), lansoprazole (Prevacid and others), pantoprazole (Protonix and others), cimetidine (Tagamet and others), famotidine (Pepcid and others) and ranitidine (Zantac and others).