What Should the Optimal Adrenaline Auto-Injector Needle Length Be?

Objective: To identify the possible subcutaneous and peri/intraosseous injection risks with different needle lengths in adults using adrenaline autoinjectors (AAI) with different needle lengths. In addition, optimum needle lengths with the lowest injection failure risk were determined for both genders. Materials and Methods: Skin-to-muscle distance (STMD) and skin-to-bone distance (STBD) were measured under minimal and maximum pressures at the anterolateral aspect of the thigh by ultrasound. Risks of subcutaneous injection, peri/intraosseous injection, and total events were calculated for both genders by taking a 15.2 mm needle length as reference for calculations. Possible subcutaneous injection and peri/intraosseous injection risks with different needle lengths were calculated and the most optimal needle lengths with the least total event risk were determined for each gender using different body mass index (BMI) threshold levels. Results: A total of 208 adults (118 women, 90 men) with a mean age of 46.3±15.7 were enrolled. BMI had the highest correlation with all ultrasonographic measures for each gender. STMDmax of 45 women (38%) and one man (1.1%) were longer than 15.2 mm. For men, total event risk was similar (3.3%) with needle lengths ranging from 12 to 18 mm. For women, considering two different BMI threshold levels with two different needle lengths (20 mm for 28 kg/m2 and 26 mm for 32 kg/m2 ) reduced total event risk to 6.7% for both BMI thresholds. Conclusion: The risk for inadequate intramuscular delivery is higher in women, especially those with higher BMI. Individualization of AAI needle lengths according to certain BMI values can improve the outcome, especially for obese women.


1. Bock SA, Munoz-Furlong A, Sampson HA. Fatalities due to anaphylactic reactions to foods. J Allergy Clin Immunol Pract 2001;107:191-3.

2. Simons FE, Ebisawa M, Sanchez-Borges M, Thong BY, Worm M, Tanno LK, et al. 2015 update of the evidence base: World Allergy Organization anaphylaxis guidelines. World Allergy Organ J 2015;8:32.

3. Muraro A, Roberts G, Worm M, Bilò MB, Brockow K, Fernández Rivas M, et al. Anaphylaxis: Guidelines from the European Academy of Allergy and Clinical Immunology. Allergy 2014;69:1026-45.

4. Simons FE, Gu X, Simons KJ. Epinephrine absorption in adults: Intramuscular versus subcutaneous injection. J Allergy Clin Immunol 2001;108:871-3.

5. Simons FE, Roberts JR, Gu X, Simons KJ. Epinephrine absorption in children with a history of anaphylaxis. J Allergy Clin Immunol 1998;101:33-7.

6. European Medicines Agency, Committee for Medicinal Products for Human Use (CHMP). Adrenaline auto-injectors Art. 31 - Assessment report for publication. Available at: http:// www.ema.europa.eu/docs/en_GB/document_library/Referrals_ document/Adrenaline_31/WC500192305.pdf. Accessed at 28.07.2019.

7. Fleming JT, Clark S, Camargo CA, Jr., Rudders SA. Early treatment of food-induced anaphylaxis with epinephrine is associated with a lower risk of hospitalization. J Allergy Clin Immunol Pract 2015;3:57-62.

8. Song TT, Nelson MR, Chang JH, Engler RJ, Chowdhury BA. Adequacy of the epinephrine autoinjector needle length in delivering epinephrine to the intramuscular tissues. Ann Allergy Asthma Immunol 2005;94:539-42.

9. Johnstone J, Hobbins S. Excess subcutaneous tissue may preclude intramuscular delivery when using adrenaline autoinjectors in patients with anaphylaxis. Allergy 2015;70:703-6.

10. Tsai G, Kim L, Nevis IF, Dominic A, Potts R, Chiu J, et al. Autoinjector needle length may be inadequate to deliver epinephrine intramuscularly in women with confirmed food allergy. Allergy Asthma Clin Immunol 2014;10:39.

11. Bhalla MC, Gable BD, Frey JA, Reichenbach MR, Wilber ST. Predictors of epinephrine autoinjector needle length inadequacy. Am J Emerg Med 2013;31:1671-6.

12. Stecher D, Bulloch B, Sales J, Schaefer C, Keahey L. Epinephrine auto-injectors: Is needle length adequate for delivery of epinephrine intramuscularly? Pediatrics 2009;124:65-70.

13. Song TT. Epinephrine needle length in autoinjectors and why it matters. J Allergy Clin Immunol Pract 2018;6:1264-5.

14. Dreborg S, Wen X, Kim L, Tsai G, Nevis I, Potts R, et al. Do epinephrine auto-injectors have an unsuitable needle length in children and adolescents at risk for anaphylaxis from food allergy? Allergy Asthma Clin Immunol 2016;12:11.

15. Dreborg S, Kim L, Tsai G, Kim H. Epinephrine auto-injector needle lengths: Can both subcutaneous and periosteal/ intraosseous injection be avoided? Ann Allergy Asthma Immunol 2018;120:648-53.

16. Duong M, Botchway A, Dela Cruz J, Austin R, McDaniel K, Jaeger C. Skin to intramuscular compartment thigh measurement by ultrasound in pediatric population. West J Emerg Med 2017;18:479-86.

17. Dreborg S, Tsai G, Kim H. Implications of variation of epinephrine auto-injector needle length. Ann Allergy Asthma Immunol 2019;123:89-94.

18. Kim L, Nevis IF, Tsai G, Dominic A, Potts R, Chiu J, et al. Children under 15 kg with food allergy may be at risk of having epinephrine auto-injectors administered into bone. Allergy Asthma Clin Immunol 2014;10:40.

19. Dreborg S, Kim H. Authors’ response. Ann Allergy Asthma Immunol 2018;121:644-5.

20. Song TT, Lieberman P. Epinephrine auto-injector needle length: What is the ideal length? Curr Opin Allergy Clin Immunol 2016;16:361-5.

21. Schwirtz A, Seeger H. Comparison of the robustness and functionality of three adrenaline auto-injectors. J Asthma Allergy 2012;5:39-49.

22. Diacono D, Pumphrey RS, Sharma V, Arkwright PD. The deep fascia of the thigh forms an impenetrable barrier to fluid injected subcutaneously by autoinjectors. J Allergy Clin Immunol Pract 2015;3:297-9.

23. Duvauchelle T, Robert P, Donazzolo Y, Loyau S, Orlandini B, Lehert P, et al. Bioavailability and cardiovascular effects of adrenaline administered by anapen autoinjector in healthy volunteers. J Allergy Clin Immunol Pract 2018;6:1257-63.

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