Stecher et al(1) state that the needle length of epinephrine auto-
injectors should be increased, based on the current recommendation to
administer epinephrine intramuscularly, and their finding that the skin-to
-muscle distance in 256 children was such that with current needle lengths
some would receive the injection subcutaneously. But their conclusion
overestimates the benefit of longer needles and fails to acknowledge the
possible risk of overpenetration.
The faster peak plasma concentration of epinephrine from
intramuscular injection(2) is unlikely to be clinically relevant except in
cases of full blown anaphylactic hypotension, a situation that is
improbable when a patient is administering epinephrine to himself. My
experience over three decades as a clinical allergist, injecting patients
with epinephrine to treat anaphylactic reactions induced by allergen
immunotherapy, is that subcutaneous epinephrine works quite well.
There is also the potential for harm with the use of longer needles.
Lippert and Wall(3), evaluating the current CDC recommendations for needle
length in pediatric immunizations, measured children’s distances not only
from skin to muscle, but also from muscle to bone. They found that use of
the currently recommended 1” or 1¼” needles for intramuscular immunization
in the thigh of children 1 year of age or older would result in
penetration into the bone or periosteum in 11% or 39% of children,
respectively. Although their data does not allow for the evaluation of
the subgroup of patients >30kg, it should serve to remind us that the
suggestion of Stecher et al to increase the needle length of auto-
injectors from 5/8” to 3cm (1.18”) has the potential to hit bone or
periosteum in patients who are lean and/or not muscular. This issue has
particular resonance for me, a lean male who experienced damage to my
supraspinatus tendon from the first flu injection I received using a 1”
rather than a 5/8” needle (case submitted for publication).
In summary, given the unproven clinical benefit of intramuscular
administration of epinephrine, particularly in cases where it would be
self administered, and the potential for bone or periosteal injury from
overpenetration, prudence would seem to be indicated before changing the
needle lengths of these devices.
Jeffrey Miller, MD
Mission: Allergy, Inc.
References:
1. Epinephrine Auto-injectors: Is Needle Length Adequate for Delivery of
Epinephrine Intramuscularly? Stecher d, Bulloch B, Sales J, Schaefer C,
Keahey L Pediatrics 2009; 124:65-70
2. Epinephrine Absorption in Children with a History of Anaphylaxis.
Simons PE, Roberts JR, Gu X, Simons KJ J Allergy Clin Immunol 1988;
101:33-37
3. Optimal Intramuscular Needle-Penetration Depth. Lippert W, Wall E
Pediatrics 2008; 122(3):e556-63
Conflict of Interest:
None declared
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