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Nausea is a sensation of queasiness and the feeling of being about to vomit. Though nausea feels as though it arises from the gastrointestinal tract, the signals that initiate its sensations originate in two areas of the brain, the chemoreceptor trigger zone and the emetic (vomiting) center. These areas are bilateral, existing in pairs on each side of the brain.
Both receive nerve and chemical input from body systems. Nausea often precedes vomiting, the forceful expulsion of upper gastrointestinal contents. However, nausea also exists without resulting in vomiting. Many medications that suppress nausea and vomiting, called antiemetic medications, block the chemical and nerve signals entering or leaving the chemoreceptor trigger zone.
Nausea is typically a symptom, a reaction such as a medication side effect, or a response such as to an irritation of the gastrointestinal tract. Severe pain such as from migraine headache, heart attack, meningitis, or injury (including postoperative pain) also activates the chemoreceptor trigger zone and the emetic center. The causes of nausea send different kinds of signals. Some antiemetic medications, such as prochlorperazine (Compazine) and meclizine (Antivert), generally target a broad range of these signals. Other medications, such as those prescribed to treat chemotherapy induced nausea and vomiting (CINV) or radiationinduced nausea and vomiting (RINV), narrowly and specifically target certain chemoreceptors.
Acupuncture, an ancient Eastern method in which the practitioner inserts hairlike needles in designated locations, is highly effective for some kinds of nausea including CINV, RINV, motion sickness, and morning sickness. Acupressure, which uses pressure applied over key acupuncture points, is also effective for many people. Other remedies for nausea include ginger and “flat” cola drinks or cola syrup.
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