Background Epinephrine delivered by an auto-injector to the anterolateral aspect of the thigh is the standard of care for the emergency treatment of anaphylaxis. For most pediatric patients in Canada, the EpipenJr is prescribed, which has a needle length of 12.7mm. The route of epinephrine administration affects its onset of action, and intramuscular delivery is recommended for rapid absorption. If epinephrine is injected subcutaneously, the absorption will be slower. Conversely, if it is injected into the bone, the absorption will be unpredictable. There are no published clinical studies assessing whether the needle length of the EpipenJr is adequate to deliver epinephrine intramuscularly in pediatric patients at risk of anaphylaxis.