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How epinephrine works to stop Anaphylaxis

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How epinephrine works to stop Anaphylaxis

admin rebekahc:
Posted: 08.08.2011 at 01:12:47

EpiPen and EpiPen Jr auto-injectors both contain the active ingredient adrenaline, which is a hormone produced naturally by the body. It is given by injection to treat a life-threatening allergic reaction called anaphylactic shock. (NB. Adrenaline is also sometimes referred to as epinephrine.)
Adrenaline is released by the adrenal glands in times of stress. It prepares the body when extra energy or exertion is needed, making the body more able to deal with life-threatening situations.
Anaphylatic shock is a severe allergic reaction that can be triggered by a drug or food allergy, or by an insect bite. A severe reaction of this type can include the following symptoms: itching of the skin, a raised rash (like a nettle rash), swelling of your lips, tongue, throat, hands and feet, flushing, weak pulse, tightening of the chest, difficulty in breathing, fall in blood pressure and in some cases loss of consciousness.
Adrenaline reverses the symptoms of anaphylaxis by acting on alpha and beta adrenergic receptors in the body.
Alpha receptors are found on the walls of blood vessels. When adrenaline stimulates these receptors this causes the blood vessels to narrow, which stops the blood pressure from falling too low. It also redirects blood to vital organs like the heart and brain.
Beta receptors are found in the heart and lungs. When adrenaline stimulates these receptors this relaxes and opens the airways, making breathing easier. It also stimulates the heart, making it beat faster and stronger.
Adrenaline also relieves itching, hives and swelling.


Last Edited by lilpig99 08.08.2011 at 01:14:05

"Those of us who were bewitched by his eloquence on the campaign trail chose to ignore some disquieting aspects of his biography: that he had accomplished very little before he ran for president." ~ Drew Westen, a professor of psychology at Emory University, on Obama, New York Times.

admin rebekahc:
Posted: 08.09.2011 at 12:47:43

VERY important to understand something which is implied (but not directly stated) in the above--

epinephrine treats the SYMPTOMS of anaphylaxis, making them more survivable.

It doesn't "stop" or "reverse" the underlying cause of the systemic allergic cascade-- ergo, emergency medical aid is STILL AN ABSOLUTE REQUIREMENT after using epinephrine, because medical providers have additional tools for supporting a person who is experiencing anaphylaxis.  (Steroids, intravenous fluids for volume depeletion, additional antihistamines and other second-messenger agonists/antagonists.)

"To travel hopefully is a better thing than to arrive." -Robert Louis Stevenson


admin rebekahc:
Posted: 08.09.2011 at 01:18:37

CM, I thought that epinepherine actually *does* stop or reverse ana in most cases. There are quite a few that require several doses and some that require additional interventions but many times one epi or two actually *does* stop or reverse ana.
I know in my son's case that is what has happened. He was having ana, got the epi and almost instantly all symptoms were totally gone and did not return. Of course he had to go to the ER, etc but he didn't require any further treatment.
Lisa - CT, USA

admin rebekahc:
Posted: 08.09.2011 at 02:21:27
Anaphylaxis itself pretty much can only be 'steered' with pharmacology and other resuscitative interventions.

Mostly, from a physiological standpoint, the point of interventions is to allow the person to survive it.  Generally (aside from unusually protracted anaphylaxis) the entire thing is over and done with in a few minutes to a few hours.

Once mast cell degranulation occurs (often pretty early on) all you can do is manage symptoms-- and the thing is that initially, it may not be clear just how bad they'll become as a result of that massive dump of second messengers (histamine, leukotrienes, etc. etc.).  That's where a beta-agonist like epinephrine comes into things-- it's supportive, and there is absolutely nothing better at maintaining open airways and cardiac sufficiency under those conditions.

Believe it or not, I was coming back to both of these threads to post this link-- the pathophysiology section of the article is particularly thorough and well-referenced:


I know that I have seen a graphic of the mast-cell/IgE-antigen second messenger cascade at some point, and I'll keep looking.  It's really much more clear where various pharmacological agents impact the pathway when seeing it all at once like that.

Last Edited by CMdeux 08.09.2011 at 02:23:49

"To travel hopefully is a better thing than to arrive." -Robert Louis Stevenson



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