Epinephrine, also known as adrenaline, is a hormone secreted by the medulla (inner part) of the adrenal glands, located on the kidneys. The adrenal glands are one of the body's endocrine glands (glands producing substances that are distributed by way of the bloodstream).

Epinephrine was the first hormone to be discovered. Hormones are substances produced by body cells that circulate in body fluid and influence the activity of cells in another part of the body. In the 1950s, the American pharmacologist Earl Sutherland (1915-1974) discovered that epinephrine does not act directly on cells, but stimulates production of cyclic AMP, a second messenger that regulates cell activity.

Epinephrine is produced continuously in small amounts by the adrenal glands, but when the body is threatened in times of excitement, danger, or emotional stress, the brain sends messages to the adrenal glands, which respond by increasing epinephrine production.

This increase in epinephrine stimulates the heart, raises blood pressure, constricts small blood vessels, releases sugar stored in the liver, and relaxes certain involuntary muscles while it contracts others. These changes in the body prepare it for "fight or flight," meaning the body is more alert, physically stronger, and has greater energy. The person is now better prepared to face the danger at hand (fight) or escape from the danger or stress (flight).

Early Research and Use

The power of adrenal extracts was first observed by the British physiologist Edward Sharpey-Schafer (1850-1935). In 1894 he injected an adrenal extract into an experimental animal, causing its blood vessels to narrow and forcing an increase in blood pressure. Japanese American chemist Jokichi Takemine (1854-1922) isolated epinephrine in 1901, based on preliminary work done in 1897 by American pharmacologist John Jacob Abel (1857-1938).

Epinephrine was soon available for medical purposes such as reviving persons suffering from hemorrhage and shock. It was once prepared using adrenal glands of animals, but is now produced synthetically.

Hormones and the Body

In 1905 the British physiologists William Bayliss (1860-1924) and Ernest Starling (1866-1927) introduced the concept of a hormone, a sub-stance that is produced by one organ and carried by the blood to another organ, where it influences its functions. Only then did scientists realize that epinephrine was a hormone.

The significance of epinephrine and other hormones in the body's operations was discovered by the American physiologist Walter Bradford Cannon (1871-1945), after he worked with injured World War I (1914-1918) soldiers. Other scientists had already studied the body as an internal environment and the interrelation of metabolism, hormones, and the immune system. In 1926 Cannon developed the concept of homeostasis (an organism's ability to remain stable internally, even when the surrounding environment exerts great stress upon it, such as hunger, thirst, and sudden danger). Homeostasis in turn led to such ideas as biofeedback (the interaction of internal and external signals and responses in the body).


Epinephrine is one of several structurally related compounds in the body called catecholamines. These compounds help regulate the sympathetic nervous system, which is part of the autonomic nervous system. The autonomic nervous system helps the body maintain homeostasis. The autonomic nervous system makes rapid adjustments to changes in environment by freeing chemical agents that act as they are released.

The endocrine system acts more slowly by releasing agents over periods of hours or days. Because it releases hormones but acts so quickly, the adrenal medulla cannot be strictly classified as part of the nervous system or part of the endocrine system. The neurohumoral theory may explain how the two act as one in many cases.

Other catecholamines are norepinephrine (also called noradrenaline or levoarterenol) and dopamine. The general function of norepinephrine seems to be the maintenance of normal blood circulation. It is also the chemical agent that is responsible for transmission of nerve impulses in the sympathetic nervous system. When a person has certain tumors of the adrenal glands, large amounts of epinephrine and norepinephrine are produced, causing a great increase in blood pressure. Dopamine is also a nerve impulse transmitter.

Synthetic (synthesized) catecholamines are important in medicine as heart stimulants and vasoconstrictors (substances that cause blood vessels to narrow), as well as relaxants of the bronchial and other muscles.


Epinephrine is one of the most powerful vasopressor (causing a rise in blood pressure) drugs known. It increases the strength of heart muscle contractions as well as the heart rate, and it constricts blood vessels and veins. Because it is a powerful heart stimulant, it is used in emergency medicine to restore heart rhythm in cases of shock and in certain cases of cardiac arrest (heart attack). The most common use of epinephrine in medicine is to relieve breathing distress in patients with asthma, bronchitis, and emphysema. The synthetic catecholamine isoproterenol is also used in the treatment of these diseases.

Epinephrine is a powerful bronchodilator, meaning it relaxes bronchial muscle. It also constricts pulmonary vessels (in the lung), and inhibits the release of histamines triggered by allergic reactions. As a bronchodilator it is most often inhaled by mouth as a spray or through another breathing apparatus. Epinephrine is also used on the skin or mucous membranes to control bleeding of wounds because it constricts blood vessels. It is sometimes used for the same reason during surgery of the nose, throat, and larynx, where it also shrinks mucosa (membranes that secrete slime), making surgery easier.

Epinephrine increases metabolism, accelerates blood coagulation, and lowers pressure inside the eye in some types of glaucoma.

User Contributions:

Alex Watson

I found this really useful and was wondering are the any ways to trigger
Epinephrine without the beformentioned effects.i.e extreme muscle stress
or casual movements that trigger Epinephrine.

Alex Watson
Tony Adamo

I have had great success caused by the educational information in the page above, but was wondering if an accidental overdose on epinephrine pills could, infact, damage parts of the body that are affected by the pill? Please get back to me on this.

Tony Adamo
Alan Bean

I have had a history with Epinephrine, and in some cases pure adreneline injections when I was young. I have been asthmatic since 1966, and still suffer with it. Albeit a good drug, and it definately has it uses, as an asthma treatment the side effects are not worth the risk these days... especially if you have high blood pressure (hypertension). The risk of stroke is too great for me. Modern drugs like Albuterol, or Salmuterol, and some of the inhaled steroids are phenomenal in treatment. You actually get longevity in relief... WITHOUT most of the side-effects...

HOWEVER - in it's day it was a LIFESAVER!

NOTE: I am NOT a Doctor, only a patient with 41 years of experience in controlling my asthma. My beliefs do NOT represent medical advice in any way! :)

I don't believe epinephrine increase metabolism. Epinephrine is the "fight or flight" hormone and when your body is in that state metabolism slows down to divert energy to vital organs such as brain and heart am I not correct?
nice artice... what are the effects of excess or deficency of epinephrine?
RE: Tomomo

When body feels that it is in danger, it increases adrenaline(epin)level to boost sugar (glucose) to your system. If you look at the receptor mechanisms that adrenaline acts on. you will understand how exactly it works.
My 24 hr urine test showed low levels of epinephrin and norepinephrine. I'm having a hardvtime finding help. What is a usual treatment? I have intense dizziness, severe loss of focus & mental fogginess and my eyes are very sensitive & feel great pressure. I've had every test there is to rule out something more serious. My doc is certain this is the problem. I just can't find much out there on raising the levels safely. Thank you in advance for your thoughts. Debbie
Is it possible to somehow get a daily dose of this or activate the medulla indefinitely?
Over dose of Epinephrine can be fatal.

be aware!
nick johnson
could epinephrine possibly be used to sure cancer or if adding certain molecules to epinephrine to cancel out the brain damage that is caused by epinephrine well brain damage only occurs in extreme doses but if you add certain amounts to certain parts of the body while inducing other chemicals at the same time to speed the process of evolution

but sorry if this is all a jumbled mess i am only 18 and i am working on my GED and plan to major in Genetics,creative writing, and engineering i dont know what kind of engineering yet im still working on it and also one more question is there a class called "creative engineering"
Just so everyone knows, and does not get confused by it, Cardiac Arrest IS NOT the same thing as a Heart Attack as indicated in the article above. Although cases of Cardiac Arrest are commonly caused by an MI, not all heart attacks result in SCA. Many people including this author tend to use them interchangeably. However an MI (Heart Attack) is caused by the occlusion of the coronary arteries via clot/plaque/spasm etc. resulting in cardiac tissue death below the site of occlusion. Cardiac Arrest is when the cardiac function suddenly ceases, most commonly caused by an arrhythmia. Epi is used in Arrest, it is CONTRAINDICATED and should be used cautiously in patients with MI's. Otherwise, a sound article.
Note to the author- Check your sources before providing false information. Nothing personal, just can not stand when people use Cardiac Arrest and MI/Heart Attack interchangeably.

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