Liza C O'Dowd, MDBurton Zweiman, MD
UpToDate performs a continuous review of over 375 journals and other resources. Updates are added as important new information is published. The literature review for version 15.2 is current through April 2007; this topic was last changed on April 28, 2006. The next version of UpToDate (15.3) will be released in October 2007.
INTRODUCTION — Allergic reactions can be triggered by foods, medications, exercise, latex, insect stings, or unknown triggers, and can cause a sudden, potentially life-threatening allergic reaction called anaphylaxis. Epinephrine (also known as adrenaline) is a medicine that treats the symptoms of serious allergic reactions. (See "Patient information: Anaphylaxis").
PATIENT AND FAMILY EDUCATION — A person with allergies, as well as his or her family, close friends, teachers, and co-workers, should learn to use an epinephrine autoinjector before it is needed. Persons suffering with anaphylaxis may panic and be unable to assist with their own injection. In addition, a quick response is necessary to prevent serious complications of anaphylaxis.
Patients should fill their epinephrine autoinjector prescription immediately, and should keep at least one epinephrine autoinjector with them at all times. It is a good idea to have an additional autoinjector at work, school, and home. Family and friends should be informed about where the home injector is stored, and it should be kept in a place that can be easily located by others in an emergency. It is also important to ensure that the injector is not expired, although an expired injector may be used if there is no alternative.
Epinephrine should be stored at normal room temperature, away from cold and heat sources. The epinephrine cartridge window should be examined periodically, to ensure that the solution is colorless and contains no floating particles. Solutions that are discolored or contain particles should be replaced.
SYMPTOMS OF ALLERGY — Allergic reaction can produce symptoms throughout the body. Skin: A sudden tingling and warm sensation, itching, flushing, urticaria (hives), and angioedema (swelling). Eyes: Itching, tearing, and swelling of the tissues around the eyes. Nose and mouth: Sneezing, runny nose, nasal congestion, itching of the mouth, and a metallic taste. Lungs and throat: Difficulty breathing, coughing, wheezing, increased airway secretions, swelling of the upper throat, hoarseness, sounds of labored breathing, and a sensation of choking. Heart: Very rapid heartbeat, arrhythmia (an irregular heart beat), low blood pressure, and cardiac arrest (a cessation of the heart's pumping action). Digestive system: Nausea, vomiting, abdominal cramps, bloating, and diarrhea. Nervous system: Dizziness, weakness, fainting, and a sense of impending doom.
WHEN TO TREAT — Persons having an allergic reaction should use their epinephrine autoinjector immediately if they: Are having trouble breathing Feel tightness in the throat Feel they might pass out
If treating a child with an allergic reaction, also use the autoinjector if the child: Is not responding or seems groggy during an allergic reaction Has food allergies and is vomiting repeatedly shortly after eating, especially if these symptoms are accompanied by flushing or hives
HOW TO TREAT — Patients should read the instructions provided with their autoinjector, and should review them each time a refill is obtained in case changes have been made. Instructions may differ from one autoinjector to another.
Epipen® or Epipen Jr.®
Sit down or lie down if possible. Stay with other people if possible. There is no need to undress, as the injector works through clothing.
1. Unscrew the cap and remove the pen from its case (show picture 1). Keep fingers away from both ends to avoid sticking them. The black end contains the needle. 2. Pull off the gray safety-release cap and form a fist around the auto-injector. The black tip should be pointing down. 3. Swing and quickly jab the black tip into the upper, outer thigh muscle and hold in place for 10 seconds to allow all the medicine to be injected (show figure 1). The cartridge window will show red. 4. Remove the pen. 5. Massage the injected area for 10 seconds. 6. Call 911 and get to the nearest emergency department immediately (patients should not drive themselves). Allergic reactions sometimes come back. 7. Replace the pen in the case, and take it to the hospital.
The Epipen® is now availabe in packages of two, in case a second dose is needed. Large-sized adults may need to repeat the dose. A second dose may also be needed if symptoms are not improving or getting worse after five minutes, or if symptoms come back before reaching the emergency department.
Twinject®
Sit down or lie down if possible. Stay with other people if possible. There is no need to undress, as the injector works through clothing.
1. Remove the pen from its grey case, keeping your fingers off both ends to avoid sticking your finger (show picture 2). 2. Pull off the green cap, labeled "1". This will reveal a grey tip, which contains a needle inside. 3. Pull off the red cap, labeled "2". 4. Form a fist around the autoinjector with the grey tip pointing down. 5. Place the grey tip against the upper, outer thigh, and press firmly until the needle enters the skin. Hold in place for 10 seconds to allow all the medicine to be injected (show figure 1). 6. Remove the injector and check the grey cap. If the needle is visible, epinephrine was given. If the needle is not present, repeat steps 4 through 5 again. 7. Massage the injected area for 10 seconds. 8. Call 911 and get to the nearest emergency department immediately (Patients should not drive themselves). Allergic reactions sometimes come back. 9. Take the pen to the hospital.
The Twinject® contains a second dose inside the cartridge. Large-sized adults may need to repeat the dose. A second dose may be needed if symptoms are not improving or getting worse after five minutes, or if symptoms come back before reaching the emergency department. Studies have shown that one in three patients will need a second dose.
To remove the inside injector: Unscrew the grey cap, taking care to avoid the needle. Hold the blue ring and pull the small injector out.
To use the second dose: Slide the yellow or orange collar off plunger at the other end. Quickly jab the injector firmly into your thigh muscle; push the plunger all the way down to inject the medicine. Remove the injector.
Injector disposal — Injectors should not be thrown away with household trash since they contain a needle. Patients should take their used injectors to a hospital or healthcare provider for proper disposal.
SIDE EFFECTS — The benefits of epinephrine in treatment of a severe allergic reaction far outweigh the risks of side effects. However, epinephrine can cause short-lived side effects in some patients. The most common side effects include the following:
Heart — Fast and/or pounding heartbeat, fleeting chest pain
Nervous system — Nervousness, trembling, feeling cold, anxiety, headache, dizziness
Digestive system — Nausea, dry throat
Lungs — Fleeting shortness of breath
FOLLOW-UP CARE — Patients can have varying responses to a severe allergic reaction. Some patients have symptoms that will resolve rapidly and completely with treatment. These patients may feel fatigued, but otherwise normal afterwards. Other patients have symptoms that take longer to resolve. For most patients, facial swelling and asthma symptoms resolve completely after 24 to 48 hours.
Some patients experience a second reaction after the initial allergic reaction, although this is not common. Second reactions can occur hours to up to four days later, although most second reactions happen within eight hours.
In most cases, the doctor may advise taking antihistamines regularly for several days after the allergic reaction. Oral corticosteroids, a type of medication that reduces inflammation, may also be prescribed. Antihistamines and corticosteroids are prescribed to treat residual symptoms; it is also possible (but not proven) that these medications can help to prevent a second reaction.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. The Food Allergy and Anaphylaxis Network
(www.foodallergy.org) American Academy of Allergy, Asthma, and Immunology
(www.aaaai.org) Anaphylaxis Foundation and Anaphylaxis Network of Canada
(www.anaphylaxis.org) The Anaphylaxis Campaign
(www.anaphylaxis.org.uk)
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