EpiPen needles too short to hit muscle in some kids.

HONOLULU -- Commercial epinephrine autoinjectors contain needles that are too short to reach the thigh muscles of a significant number of children, results of a study show.

Penlike autoinjectors, which deliver epinephrine to at-risk children and adults to treat symptoms of anaphylaxis, have become a mainstay of rapid response to severe allergic reactions.

Past research showed that peak plasma concentration is attained far more quickly (8 minutes vs. 34 minutes) when epinephrine is delivered intramuscularly versus subcutaneously (J. Allergy Clin. Immunol. 2001;108:871-3).

The EpiPen Jr., designed for children who weigh less than 30 kg, and the EpiPen, used for children and adults who weigh 30 kg or more, contains spring-loaded needles that measure 1/2-inch and 5/8-inch, respectively. Both devices are made by Dey, L.P. of Napa, Calif. At press time, the company was preparing a response regarding the study.

Dr. Dawn S. Stecher, an emergency medicine physician at Phoenix Children's Hospital, and her associates measured by ultrasound linear array transducer the distance between the skin surface and the vastus lateralis muscle (the largest part of the quadriceps muscle) in the upper thighs of 128 girls and 128 boys in a healthy, convenience sample of children between ages 1 and 12 years who presented to the hospital's radiology department or emergency department for reasons unrelated to the study.

The sample mostly comprised Hispanic and white children, with roughly even numbers in each group, plus 4% African American subjects and 4% of other race/ethnicity.

The children's ages ranged from 12 to 153 months, with the average age of 7 years.

Seventy children (27% of the sample) were overweight, and 25 (10%) were at risk for overweight, according to Centers for Disease Control and Prevention guidelines.

The needle of the EpiPen Jr. would be too short to reach muscle in 19, or 12%, of 158 children who weighed less than 30 kg. Among the 98 children who weighed 30 kg or more, and would therefore be prescribed the adult EpiPen, the needle length would be insufficient to reach muscle in 29 children (30%).

In a logistic regression analysis, body mass index (BMI) was the only independent predictor of whether the appropriate EpiPen needle would reach muscle tissue, Dr. Stecher reported at the annual meeting of the Pediatric Academic Societies.

"The needles on current EpiPen autoinjectors are not long enough to reach muscle in a significant number of children," she concluded in her oral presentation.

She recommended development of autoinjectors of "varying needle lengths, based on BMI, to ensure that children are receiving epinephrine properly."

Previous research has found that adult EpiPens are of insufficient length to reach muscle in more women than men, regardless of BMI, but no gender differences were seen in children, noted Dr. Stecher.

In response to a question from the audience, she said that she also reviewed the measurement data with regard to Twinject, an autoinjection system made by Verus Pharmaceuticals, but determined that its needles are even shorter than those in EpiPen injectors.

Dr. Stecher reported no financial disclosures with regard to her presentation.

BY BETSY BATES

Los Angeles Bureau