Why Chemotherapy Causes Nausea and Vomiting


Nausea and vomiting are quite common after chemotherapy. They are often associated with the worst memories of treatment. Nausea and vomiting can also be dangerous for health – leading to a variety of other health complications. Why does chemotherapy cause nausea and vomiting?


Triggering the Vomiting Center

Nausea and vomiting, like most other things that we do, are controlled by the brain. Vomiting is triggered from a spot in the brain called the vomiting center. There are several signals that can make the vomiting center cause a person to throw up:​

  • Signals from an area of the brain called the chemoreceptor trigger zone (CTZ) that reacts to chemicals or drugs in the blood.
  • Signals from the brain cortex and limbic system that reacts to sight, taste, and smell, as well as to emotions and pain.
  • Signals from a part of the ear that responds to motion (and so causes motion sickness in some people).
  • Signals from some other organs and nerves that respond to disease or irritation in these organs. In chemotherapy, it has been noted that there are areas in the esophagus, stomach, and intestines that are triggered.

These signals are transmitted with the help of chemical substances called neurotransmitters that travel via blood and nerves and reaches the brain.

Nausea and Vomiting with Chemotherapy

The most important cause of chemotherapy-induced nausea and vomiting is the activation of the chemoreceptor trigger zone (CTZ) by the chemotherapy agents circulating in the blood. But the other pathways are also involved. The sight and smell of chemotherapy are the main causes of ‘anticipatory nausea and vomiting’, that occurs before chemotherapy is delivered in those who have had bad spells of vomiting with chemotherapy in prior cycles.

Risk Factors for Nausea and Vomiting with Chemotherapy

  • You are more likely to experience this side effect if you have had previous episodes with past chemotherapy treatments, motion sickness, or vomiting with pregnancy.
  • It’s more common in younger patients and female patients.
  • If your fluid balance is off because you are dehydrated or bloating, you are more likely to experience it.
  • Constipation is a risk factor, as is taking opioid drugs, which cause constipation.
  • Infections
  • Kidney diseases
  • Location of tumors: digestive tract, brain, liver.

Onset and Treatment

Nausea and vomiting may occur at any point during chemotherapy treatment. It can happen within 24 hours of beginning chemotherapy or later. In the first 24 hours, it’s labeled acute, if later it is labeled delayed.

Anticipatory nausea and vomiting often start happening after three or four treatments. It can be triggered by anything in the treatment area, including particular smells, seeing care providers or equipment, and the typical sounds in the area. You don’t even have to start the procedure for these to set off an episode.

Antinausea drugs are used to prevent chemotherapy nausea and vomiting. They vary in how long they have an effect and when you would take them. They include prochlorperazine, droperidol, metoclopramide, and marijuana or Marinol. Natural treatments can also be tried, including ginger root.

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