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a hormone produced by the adrenal medulla; called also adrenaline (British). Its function is to aid in the regulation of the sympathetic branch of the autonomic nervous system. At times when a person is highly stimulated, as by fear, anger, or some challenging situation, extra amounts of epinephrine are released into the bloodstream, preparing the body for energetic action. Epinephrine is a powerful vasopressor that increases blood pressure and increases the heart rate and cardiac output. It also increases glycogenolysis and the release of glucose from the liver, so that a person has a suddenly increased feeling of muscular strength and aggressiveness.ƒ

Some disorders of the adrenal glands, such as addison's disease, reduce the output of epinephrine below normal. By contrast, excessive activity of those glands, as sometimes seen in highly emotional persons, tends to produce tenseness, palpitation, high blood pressure, perhaps diarrhea, and overaggressiveness. Certain adrenal tumors also result in the production of too much epinephrine. Removal of the tumor relieves symptoms.

Epinephrine is also produced synthetically and can be administered parenterally, topically, or by inhalation. It acts as a vasoconstrictor, antispasmodic, and sympathomimetic, and it is used as an emergency heart stimulant as well as to relieve symptoms in allergic conditions such as urticaria (hives), asthma, and other conditions requiring bronchodilation and as a adjunct to local and regional anesthesia. It is the most effective drug for counteracting the lethal effects of anaphylactic shock. It is also used topically in the eye in the treatment of glaucoma.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


A trademark for a preparation of epinephrine.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.