For many people who have been diagnosed with cancer, therapy administered using cytotoxic (chemotherapeutic) agents will play a crucial role in their curative or palliative treatment. Although cytotoxic therapies are beneficial for cancer patients, many people believe that it leads to chronic nausea and vomiting. Earlier, most patients who were administered chemotherapy experienced moderate to acute digestive tract irritation and vomiting, but that does not apply to current treatment procedures. Presently, new types of cytotoxic agents are being administered along with advanced drugs that efficiently alleviate side-effects. They have made it more comfortable for patients to receive chemotherapy-based treatments.
Nausea and Vomiting: Their Relationship with Brain Signals
What causes nausea and vomiting? Directly or indirectly, the brain controls all bodily functions and the same applies to stomach upset and vomiting. The act of vomiting is controlled by a specific region within the brain, generally referred to as the vomiting center. This site lies on the floor of the fourth ventricle, a location within the brain called the area postrema. This neurological center comprises of an array of receptor cells that can result in nausea and vomiting when stimulated. Also called a circumventricular organ, the area postrema is located outside the blood brain barrier. This implies that it can receive stimulation from blood-borne cytotoxic agents among other things. Along with stimulation received from chemotherapies, the area postrema can also lead to side-effects (induce vomiting) due to signals received from other anatomical sites such as:
- The cerebral chemoreceptive trigger zone (CTZ) which can be stimulated by drugs, chemicals, or foreign matter present in the bloodstream
- Organs in the digestive tract and nerves that respond to disease or chemotherapeutic discomfort
- Limbic system receptor sites and cerebral cortex that are stimulated by pain, emotional discomfort, odors, sight and taste sensations
- Internal ear receptors that react to motion
Stimulations and reactions associated with the vomiting center occur when receptor cells come in contact with specific chemical compositions called neurotransmitters. These neurotransmitters travel to the area postrema carrying several different instructions that can induce varied types of nausea and vomiting symptoms such as:
- Breakthrough vomiting – This refers to chronic nausea and vomiting that prevails even after antiemetic (anti-nausea) drugs and other therapies have been administered
- Acute nausea and vomiting – This relates to stomach discomfort and vomiting that occurs within a few hours after chemotherapy is administered
- Delayed nausea and vomiting – These side-effects take 24 hours or more to manifest after chemotherapy is administered
- Anticipatory vomiting – This refers to a general behavior noticed among some patients who experience nausea and vomiting just prior to the start of the chemotherapy session
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