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Thursday, July 16, 2009

EpiPen

A 0.3 mg EpiPen auto-injector.EpiPen is a registered trademark for a commonly used autoinjector of epinephrine (a.k.a. adrenaline), used in medicine to treat anaphylactic shock.
Anaphylaxis is an acute systemic (multi-system) and severe type I hypersensitivity allergic reaction in humans and other mammals. The term comes from the Greek words ανα ana (against) and φύλαξις phylaxis (protection).[1] Minute amounts of allergens may cause a life-threatening anaphylactic reaction. Anaphylaxis may occur after ingestion, skin contact, injection of an allergen or, in some cases, inhalation.[2]

Anaphylactic shock, the most severe type of anaphylaxis, occurs when an allergic response triggers a quick release from mast cells of large quantities of immunological mediators (histamines, prostaglandins, leukotrienes) leading to systemic vasodilation (associated with a sudden drop in blood pressure) and edema of bronchial mucosa (resulting in bronchoconstriction and difficulty breathing). Anaphylactic shock can lead to death in a matter of minutes if left untreated.

Due in part to the variety of definitions, an estimated 1.24% to 16.8% of the population of the United States is considered "at risk" for having an anaphylactic reaction if they are exposed to one or more allergens, especially penicillin and insect stings. Most of these people successfully avoid their allergens and will never experience anaphylaxis. Of those people who actually experience anaphylaxis, up to 1% may die as a result.[3] Anaphylaxis results in approximately 1,500 deaths per year in the U.S.[4] (one out of every 1,600 of the 2.4 million deaths from all causes each year in the U.S.;[5]). The most common presentation includes sudden cardiovascular collapse (88% of reported cases of severe anaphylaxis).

Researchers typically distinguish between "true anaphylaxis" and "pseudo-anaphylaxis" or an "anaphylactoid reaction." The symptoms, treatment, and risk of death are identical, but "true" anaphylaxis is always caused directly by degranulation of mast cells or basophils that is mediated by immunoglobulin E (IgE), and pseudo-anaphylaxis occurs due to all other causes.[6] The distinction is primarily made by those studying mechanisms of allergic reactions.

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