EpiPen

From Chempedia

EpiPens

EpiPens are self auto-injectors that are prescribed by a physician for the emergency treatment of allergic reactions, or for individuals with a history of anaphylactic reactions.^[1] Anaphylactic reactions, or anaphylactic shock, are the most severe types of acute allergic reactions. It is life-threatening unless treated immediately.^[2]

Anaphylactic shock occurs when a person has been exposed to an allergen, a protein that is viewed as an invader by the immune system.^[3] Symptoms of an allergic reaction include hives, swelling of areas such as the throat and tongue, difficulty breathing or swallowing, metallic taste in the mouth, flushing, itching, increase in heart rate, severe drop in blood pressure, and loss of consciousness. One or more of these symptoms could result in anaphylactic shock. Exposure typically occurs by an individual ingesting a substance he or she is allergic to, such as, peanuts, dairy, tree nuts, fish, shellfish, medication, or if an individual is stung by a bee or wasp. "Upon the first exposure, plasma cells begin to secrete IgE specific for the allergen."^[4] Mast cells, non-circulating cells found in connective tissue, are attached to these antibody tails. Then upon second exposure, "the allergen binds to IgE already on the mast cell" and triggers a rapid reaction releasing histamine and other inflammatory agents.^[5] Histamine causes dilation and an increase in the permeability of small blood vessels.^[6] An allergic reaction takes only 1-2 minutes to escalate to anaphylactic shock.^[7]

When your body goes into anaphylactic shock, most physicians believe that the best way to stop it is through use of an EpiPen. Epinephrine, preservatives, and water are present in the EpiPen, but epinephrine is the only chemical responsible for stopping the shock. "Epinephrine is a catecholamine hormone, a sympathomimetic monoamine derived from tyrosine and phenylalanine"^[8], which are two of the twenty amino acids that make up the proteins in the body. Sympathomimetics are a group of drugs that act as those of a stimulated nervous system.^[9] Although Epinephrine is produced naturally in the body, it can be synthetically produced and prescribed for the use in an EpiPen. The synthetic production of epinephrine employs the Friedel-Crafts reaction of acylation, the process of adding an acyl group to a compound of catechol, with chloroacetyl chloride. "This process yields chloracetocatechol. Displacement of the chlorine by methylamine yields the methylamine derivative, adrenaline, which on catalytic reduction yields epinephrine."^[10] Synthetic production of epinephrine allows people with allergic reactions to deliver epinephrine via an auto-injector into their bodies to help stop anaphylactic shock.

When epinephrine is delivered via an auto-injector (0.30 mg or 0.15 mg, depending on your weight), it begins to work quickly to reverse the symptoms of an anaphylactic reaction. Epinephrine targets two types of receptors on the targeted cells, alpha and beta. When the receptors come into contact with the adrenaline, they cause the heart rate to increase, the pupils to dilate, and the blood flow to increase to the extremities of your body rather than towards the central organs. Also, by binding to the alpha receptors of liver cells, the phosphorylation of insulin is signaled, which causes an increase in blood sugar levels. By binding to the beta receptors of muscle and liver cells, glycogen is broken down to glucose, the monosaccharide used in the body for energy production. The epinephrine also relaxes muscles in the lungs to help with breathing, as well as the termination of swelling and hives around the face, symptoms of a severe allergic reaction. An injection of Epinephrine also stops cardiac arrest and asthma. Anaphylactic shock can be swift and potentially deadly due to the histamine released in the body if not stopped by an epinephrine injection.^[11]

Epinephrine injections are injected into the thigh. The injections are filled with a single dose of epinephrine and are only to be used when a person is encountering a life threatening allergic reaction. After the EpiPen has been injected, a person may experience some side effects from the epinephrine, such as upset stomach, vomiting, sweating, nervousness, and dizziness. Some other side effects include weakness, pale skin, headache, and shaking hands. If a person experiences problems in breathing or irregular heartbeats, he or she should contact a doctor immediately.^[12] The person should also contact a doctor if a second dose is required.

It is unclear how many people experience allergies that put people at risk for anaphylactic shock each year, but it may be as high as 40.9 million. Each year 40-400 deaths occur due to insect stings, 125 deaths related to food allergies, and 5,400 deaths from penicillin. Penicillin related deaths account for an estimated 75% of US allergy deaths each year.^[13]In order to decrease these numbers, individuals with allergies that could allow anaphylactic shock to occur must understand how to use the EpiPen correctly. EpiPens should be used as soon as possible when an allergic reaction begins, but should not replace medical care.

Footnotes

1. ^ Dey, L.P. Launches New Patient Friendly Packaging and Labeling for All Epipen and Epipen Jr. Auto-Injectors. PR Newswire Association LLC. [Online] 2005, 1.

2. ^ Campbell, N.A. Biology, 4th ed.; The Benjamin/Cummings Publishing Company, Inc: California, 1996.

3. ^ Epipen.com, About Anaphylaxis, What is Anaphylaxis ? http://www.epipen.com/anaphylaxis_whatis.aspx (accessed Sept. 2005).

4. ^ Chemistry Daily, Epinephrine. http://www.chemistrydaily.com/chemistry/Epinephrine (accessed Sept. 2005).

5. ^ Wikepedia, Sympathomimetics. http://en.wikipedia.org/wiki/Sympathomimetics (accessed Nov. 2005).

6. ^ Wiley InterScience, Epinephrine and Norepinephrine. http://www.mrw.interscience.wiley.com/kirk/articles/epinpugs.a01/abstract-fs.html (accessed Nov, 2005).

7. ^ Epinephrine: Dramatic Results for the Fatally Unpredictable. http://www.chem.yorku.ca/hall_of_fame/essays99/epinephrine.htm (accessed Oct. 2005).

8. ^ Medline Plus, Drug Information, Epinephrine Injection. http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a603002.html (accessed Oct. 2005).

“Researched and written by: Amanda Herrmann, Melissa Herron, Scott Baker, and Amanda Hinrichs”