Why Do Nausea and Vomiting Occur With Chemotherapy?

Learn how chemotherapy triggers the vomiting center of your brain

Nausea and vomiting are quite common after chemotherapy. They are often associated with the worst memories of treatment. Nausea and vomiting can also lead to other health complications, including dehydration and malnutrition.

This article explains why chemotherapy causes nausea and vomiting and provides some helpful tips for managing these symptoms.

Woman vomiting into bucket from bed
Image Source / Getty Images

Triggering the Vomiting Center

Nausea and vomiting 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) reacts to chemicals or drugs in the blood.
  • Signals from the cerebral cortex and limbic system react to sight, taste, smell, emotions, or pain.
  • Signals from a part of the ear that responds to motion may cause motion sickness in some people.
  • Signals from other organs and nerves respond to disease or irritation. It has been noted that there are areas in the esophagus, stomach, and intestines that are triggered by chemotherapy.

These signals are transmitted by neurotransmitters that travel via blood and nerves.

Nausea and Vomiting with Chemotherapy

Several pathways are involved in chemotherapy-induced nausea and vomiting.

  • 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.
  • The sight and smell of chemotherapy are the main causes of anticipatory nausea and vomiting, that affect people 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 nausea and vomiting as a side effect of your chemotherapy treatment if you have had previous episodes with past chemotherapy treatments, if you are prone to motion sickness, or if you've had vomiting with pregnancy. It's also more common in younger patients and female patients.

Other factors that can make you more susceptible to nausea and vomiting from chemotherapy:

  • Dehydration or bloating, which can affect your electrolyte and fluid balance
  • Constipation or taking opioid drugs, which cause constipation
  • Infections
  • Kidney diseases
  • Location of tumors in the digestive tract, brain, or 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 include options such as prochlorperazine, droperidol, metoclopramide, marijuana or marijuana derivatives, and natural supplements.

Anti-Emetics

Anti-emetics are medications that are used to prevent or treat nausea. Most oncologists will give anti-emetics with the chemotherapy infusion, to prevent this side effect.

You may also be prescribed anti-emetics to take at home as needed. It can be difficult to swallow a tablet if you are feeling nauseous, and many of these medications come in dispersible tablets that will dissolve and become absorbed under your tongue or in suppository form.

Marijuana Derivatives

The marijuana plant flower has naturally occurring molecules, the most famous of which is THC-9 (delta-9-tetrahydrocannabinol). THC-9 has powerful analgesic, anti-emetic (anti-nausea), and appetite stimulant effects.

Dronabinol is a synthetic form of THC-9. Studies done with Dronabinol have shown modest effects on nausea control and appetite stimulation.

Natural Remedies

You can also try ginger root and other natural remedies. However, with some chemotherapeutic agents like Cisplatin or Cyclophosphamide, the chances of developing severe nausea are so high that stronger pharmaceuticals will most likely be needed to control it.

You should make sure you have had a conversation with your oncologist or supportive health staff and have a clear plan and availability of medications in the event that your chemotherapy is accompanied by or followed by episodes of severe nausea.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Tsuji D, Suzuki K, Kawasaki Y. Risk factors associated with chemotherapy-induced nausea and vomiting in the triplet antiemetic regimen including palonosetron or granisetron for cisplatin-based chemotherapy: analysis of a randomized, double-blind controlled trialSupportive Care in Cancer. 2018;27(3):1139-1147. doi:10.1007/s00520-018-4403-y

  3. Mustian KM, Devine K, Ryan JL. Treatment of Nausea and Vomiting During ChemotherapyUS Oncol Hematol. 2011;7(2):91–97. doi:10.17925/ohr.2011.07.2.91

Additional Reading

By Indranil Mallick, MD
 Indranil Mallick, MD, DNB, is a radiation oncologist with a special interest in lymphoma.