bilateral, existing in pairs on each side of the
brain. Both receive NERVEand 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 sup-
press nausea and vomiting, called ANTIEMETIC MED-
ICATIONS, 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 postopera-
tive 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 (Com-
pazine) 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 radiation-
induced 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 GINGERand “flat” cola
drinks or cola syrup.
See also CYCLIC VOMITING SYNDROME; FOOD-BORNE
ILLNESSES; GASTROENTERITIS.78 The Gastrointestinal System