Researchers report new results on anaphylaxis treatment

New findings related to the treatment of anaphylaxis were covered at the recent 2004 Annual Meeting of the American Academy of Allergy, Asthma & Immunology (AAAAI) in San Francisco. Anaphylaxis is a severe allergic reaction that causes difficulty in breathing, loss of consciousness, and even death.

The most common substances to trigger this medical emergency are foods, insect stings, and medications. Symptoms typically begin within minutes of exposure, and range from hives, skin redness, vomiting, diarrhea, and feeling of "impending doom" to wheezing, chest pain, low blood pressure, and shock.

Anaphylaxis occurs when the immune system overreacts to an allergen, a normally harmless substance to which the person is allergic. When first exposed to the allergen, the body produces Immunoglobulin E (IgE) antibodies specific to the allergen. The antibodies then attach themselves to mast cells. When the body is exposed to the allergen again, the IgE antibodies can detect it, and they work to destroy it by causing the release of histamine and other chemicals from the mast cell. While these chemicals are necessary for destruction of the allergen, they also cause anaphylaxis if released in large quantities.

According to the protocols developed by the Joint Task Force on Practice Parameters, including the AAAAI; the American College of Allergy, Asthma & Immunology; and the Joint Council of Allergy, Asthma & Immunology, the recommended treatment for anaphylaxis is intramuscular epinephrine, a route preferred to subcutaneous administration because it provides faster onset and higher blood levels. The recommended dose is 0.2 to 0.5 mg in adults and 0.01 mg/kg in children. However, according to results of a survey presented at the AAAAI meeting, pediatricians may not be treating anaphylaxis as effectively as they could. The survey, based on a case of a child presenting with anaphylaxis symptoms, found more than 90% of the pediatricians who responded would administer epinephrine as initial treatment but less than 50% would give it intramuscularly. Only 44% would observe the child in the emergency department for the recommended four hours after treatment.

Researchers at the William Beaumont Army Medical Center, El Paso, Texas, found similar results. A review of records of patients admitted with anaphylaxis found that only 52% of the episodes were treated with epinephrine, none administered intramuscularly. At discharge only 32% of patients received Rxs for epinephrine self-injectors; 16% received documented instructions on its use.

Elisabeth Andrews, R.Ph., a retail pharmacist in New London, Conn., agrees that patients and parents need more education on proper use of epinephrine self-injectors. Parents rarely ask for instruction on operating the injectors even though injection trainers are available at most pharmacies, she said, and parents need to feel so comfortable with the injector that they don't panic during stressful moments when epinephrine is urgently needed.

At the meeting, Alkermes Inc. presented results from its phase I trials of inhaled epinephrine. The dry powder is administered via an inhaler similar to those used for treating asthma. According to the company, the epinephrine was rapidly absorbed, producing clinically effective blood levels.

Another treatment under investigation is sublingual epinephrine. According to a study presented at the meeting, researchers at the University of Manitoba compared the sublingual and subcutaneous absorption of epinephrine in healthy men. Comparison, based on epinephrine levels, blood pressure, and heart rate, found epinephrine was absorbed sublingually without serious adverse effects.

Patients with allergies to environmental allergens can receive immunotherapy, consisting of solutions containing natural substances to which the patient is allergic, to desensitize them. Unfortunately, this type of desensitization is usually not possible for food allergies. A recent study, "Effect of Anti-IgE Therapy in Patients with Peanut Allergy" (NEJM 2003; 348:986-993), examined the effectiveness of monoclonal antibody against IgE in preventing peanut-induced anaphylaxis. Patients with known hypersensitivity to peanuts were given varied doses of the monoclonal antibody, then orally challenged with increasing quantities of peanut flour. The patients receiving the highest dose of antibody exhibited an increased threshold of sensitivity to peanuts from a level equivalent to one-half peanut to almost nine peanuts. While these patients were not desensitized to peanuts, the increased threshold would translate into protection from accidental ingestion.

While research continues on these improved treatment options, experts say healthcare providers must ensure the health of patients prone to anaphylaxis. They should strive to provide optimal treatment and to educate patients on symptoms of anaphylaxis and the use of self-injectors.