(HealthDay News) — Given the increasing epidemic of obesity, epinephrine autoinjectors (EAIs) for anaphylaxis require longer needles to ensure intramuscular injection, according to a study published online February 13 in Allergy.

Jamie Johnstone, from New Cross Hospital in Wolverhampton, U.K., and colleagues examined the depth of subcutaneous tissue in a population of patients with anaphylaxis. The authors performed ultrasound and measurements of skin-to-muscle depth (STMD) at anterolateral thigh and anterior thigh in 28 patients (23 female; age range, 18–75 years) already prescribed EAIs for anaphylaxis.

The researchers found that using the recommended administration site of the anterolateral thigh, for 68% of patients the STMD was greater than the EAI needle length (15.02mm). Female gender and body mass index over 30kg/m² were key predictors for increased STMD.

“EAIs require longer needles to ensure intramuscular administration and ultrasound at point of prescription would aid needle length selection,” the authors write.

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