Nausea and Vomiting (PDQ®)

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This patient summary on nausea and vomiting is adapted from the summary written for health professionals by cancer experts. This brief summary describes the causes and treatment of nausea and vomiting, two of the most upsetting side effects for patients with cancer. This and other accurate, credible information about cancer treatment, screening, prevention, supportive care, and ongoing clinical trials, is available online at NCI's Web site.

This summary is about nausea and vomiting in adults with cancer.


Nausea is an unpleasant wavelike feeling in the back of the throat and/or stomach that may or may not result in vomiting. Vomiting is the forceful elimination of the contents of the stomach through the mouth. Retching is the movement of the stomach and esophagus without vomiting and is also called dry heaves. Although treatments have improved, nausea and vomiting continue to be worrisome side effects of cancer therapy. Nausea may be even more distressing for patients than vomiting.

It is very important to prevent and control nausea and vomiting in patients with cancer. Uncontrolled nausea and vomiting can interfere with the patient's ability to receive cancer treatment and care for himself or herself by causing chemical changes in the body, loss of appetite, physical and mental difficulties, a torn esophagus, broken bones, and the reopening of surgical wounds.

Nausea and vomiting that are caused by cancer therapy are classified as follows:

Acute nausea and vomiting: Usually occurs within 24 hours after beginning chemotherapy.

Delayed nausea and vomiting: Occurs more than 24 hours after chemotherapy. Also called late nausea and vomiting.

Anticipatory nausea and vomiting: If a patient has had nausea and vomiting after the previous 3 or 4 chemotherapy treatments, he or she may experience anticipatory nausea and vomiting. The smells, sights, and sounds of the treatment room may remind the patient of previous episodes and may trigger nausea and vomiting before a new cycle of chemotherapy (or radiation therapy) has even begun.

Chronic nausea and vomiting: May affect people who have advanced cancer. It is not well understood.

Studies strongly suggest that patients receiving chemotherapy experience more acute and delayed nausea and vomiting than is estimated by health care providers.


Nausea is controlled by a part of the central nervous system that controls involuntary bodily functions. Vomiting is a reflex controlled by a vomiting center in the brain. Vomiting can be stimulated by various triggers, such as smell, taste, anxiety, pain, motion, poor blood flow, irritation, or changes in the body caused by inflammation.

The most common causes of nausea and vomiting are:

Nausea and vomiting are more likely to occur if the patient:

Anticipatory Nausea and Vomiting

Anticipatory nausea and vomiting occur after the patient has undergone several cancer treatments. It occurs in response to triggers, such as odors in the therapy room. For example, a person who begins chemotherapy and smells an alcohol swab at the same time, may later experience nausea and vomiting at the smell of alcohol alone. Patients usually do not experience nausea and/or vomiting before or during chemotherapy until after they have received several courses of treatment. The following factors may help predict which patients are more likely to experience anticipatory nausea and vomiting:

  • Being younger than 50 years.
  • Being female.
  • The severity of nausea and vomiting after the last chemotherapy session.
  • Feeling warm or hot after the last chemotherapy session.
  • A history of motion sickness.
  • Feeling dizzy or lightheaded after chemotherapy.
  • Sweating after the last chemotherapy session.
  • Experiencing weakness after the last chemotherapy session.
  • Having a high level of anxiety.
  • The type of chemotherapy (some are more likely to cause nausea and vomiting).
  • Having morning sickness during pregnancy.

Acute Nausea and Vomiting

Chemotherapy is the most common treatment-related cause of nausea and vomiting. The drug, dose, schedule of administration, route, and factors that are unique to the patient all determine how often nausea occurs and how severe it will be. Usually, these symptoms can be prevented or controlled.

Acute nausea and vomiting are more likely to occur in patients who:

  • Have experienced nausea and vomiting after previous chemotherapy sessions.
  • Are female.
  • Drink little or no alcohol.
  • Are young.

Delayed Nausea and Vomiting

Delayed nausea and vomiting occurs more than 24 hours after chemotherapy. It is more likely to occur in patients who:

Drugs to prevent nausea and vomiting may be given alone or in combinations to patients who are receiving chemotherapy.

Nausea and Vomiting in Advanced Cancer

Patients who have advanced cancer commonly experience chronic nausea and vomiting, which can significantly impair quality of life. Nausea and vomiting related to advanced cancer may be caused by the following:

Radiation Therapy and Nausea and Vomiting

Radiation therapy may also cause nausea and vomiting, especially in patients who are undergoing radiation to the GI tract (particularly the small intestine and stomach) or brain. The risk for nausea and vomiting increases as the dose of radiation and area being irradiated increase. Nausea and vomiting associated with radiation therapy usually occurs one-half hour to several hours after treatment. Symptoms may improve on days the patient does not undergo radiation therapy.


Anticipatory Nausea and Vomiting

Treatment of anticipatory nausea and vomiting is more likely to be successful when symptoms are recognized and treated early. Although antinausea drugs do not seem to be effective, the following may reduce symptoms:

Acute/Delayed Nausea and Vomiting

Acute and delayed nausea and vomiting are most commonly treated with antinausea drugs. Some drugs last only a short time in the body, and need to be given more often; others last a long time and are given less frequently. Blood levels of the drug(s) must be kept constant to control nausea and vomiting effectively.

The following drugs are commonly given alone or in combinations to treat nausea and vomiting:

Nausea and Vomiting Related to Constipation and Bowel Obstruction in Advanced Cancer

In patients with advanced cancer, constipation is one of the most common causes of nausea. To prevent constipation and decrease the risk for nausea and vomiting, it is important that a regular bowel routine be followed, even if the patient isn't eating. High-fiber diets and bulk-forming laxatives with psyllium or cellulose require large amounts of fluid, however, and are not well tolerated by patients with advanced cancer. Laxatives that soften the stool or stimulate the bowel may be prescribed to prevent constipation, especially if the patient is being treated with opioids for cancer pain. The use of enemas and rectal suppositories is limited to short-term, severe episodes of constipation. Patients who have a loss of bowel function because of nerve damage (such as a tumor pressing on the spinal cord) may require suppositories for regular bowel emptying. Enemas and rectal suppositories should not be used in patients who have damage to the bowel wall. (Refer to the Constipation section in the PDQ summary on Gastrointestinal Complications and the Side Effects of Opioids section in the PDQ summary on Pain.) Severe constipation may result in bowel obstruction.

Malignant Bowel Obstruction

Patients who have advanced cancer may develop a bowel obstruction that cannot be removed with surgery. The doctor may insert a nasogastric tube through the nose and esophagus into the stomach to temporarily relieve a partial obstruction. If the obstruction completely blocks the bowel, the doctor may insert a gastrostomy tube through the wall of the abdomen directly into the stomach to relieve fluid and air build-up. A gastrostomy tube also allows medications and liquids to be given directly into the stomach by pouring them down the tube. Sometimes, the doctor may create an ileostomy or colostomy by bringing part of the small intestine or colon through the abdominal wall to form an opening; or an expandable metal tube called a stent may be inserted into the bowel to open the blocked area. Injections or infusions of medications may be prescribed to relieve pain and/or nausea and vomiting.

Alternative Therapies for Nausea and Vomiting

Nausea and vomiting may be controlled without using drugs. The following may be helpful in relieving symptoms, especially for anticipatory nausea and vomiting, and may improve the effectiveness of antinausea drugs.

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