Epi Shots May Work Better in Lower Thigh of Obese Kids

SAN ANTONIO, TX – If a person experiences a serious, life-threatening allergic reaction called anaphylaxis, immediate medical attention is required, including an injection of epinephrine and a trip to a hospital emergency room for follow up care. Epinephrine typically comes as a single-dose pre-filled automatic injection device, which is inserted into the thigh. In children who are overweight or obese, research from the 2013 Annual Meeting of the American Academy of Allergy, Asthma & Immunology (AAAAI) found that the lower rather than upper thigh may be a more favorable site to administer this vital medication.

“Delivering epinephrine into the muscle allows for more rapid absorption and leads to higher blood levels than if it’s injected into the overlying fat. Considering the rising obesity rates in children, there is concern that epinephrine auto-injectors will not adequately deliver the medication in overweight children who may be experiencing anaphylaxis,” said first author Peter Arkwright, MD, PhD, FAAAAI. “Without proper treatment, anaphylaxis can be fatal, so it’s extremely important that epinephrine is administered quickly and effectively.”

Dr. Arkwright and colleagues from the University of Manchester and Royal Manchester Children’s Hospital in the United Kingdom used ultrasound to take skin surface to muscle depth measurements at set distances down the thigh and leg of 93 children. They also measured weight, height, waist circumference and body mass index (BMI).

After statistical analysis of this pediatric sample, the researchers found that higher weight and waist circumference were linked to a skin surface to muscle depth measurement greater than the length of the auto-injector needle. At one quarter down the thigh, 82% of the obese children studied had skin surface to muscle depth greater than needle length. This was only true for 25% of the non-obese children.

Yet three quarters down the thigh, skin surface to muscle depth surpassed the length of the auto-injector needle in only 17% of obese children and 2% of those not obese.

“Based on our study, injecting epinephrine into the lower rather than upper thigh would be advised in overweight or obese children,” explained Dr. Arkwright. “If a child is experiencing anaphylaxis, this information would be important for a caregiver to know so that epinephrine can be administered into the child’s muscle in the most effective way.”

The AAAAI represents allergists, asthma specialists, clinical immunologists, allied health professionals and others with a special interest in the research and treatment of allergic disease.

Established in 1943, the AAAAI has more than 6,700 members in the United States, Canada and 60 other countries.

A link to all abstracts presented at the Annual Meeting is available at www.annualmeeting.aaaai.org.