The TEN study: time epinephrine needs to reach muscle

Area of Science:

• Anaphylaxis and Emergency Medicine
• Pharmacology and Drug Delivery

Background:

• Epinephrine autoinjectors (EAIs) are crucial for treating anaphylaxis, delivering epinephrine to the vastus lateralis muscle.
• Studies indicate frequent user errors with EAIs, particularly premature removal from the injection site.
• Optimizing EAI use is vital for effective emergency treatment.

Purpose of the Study:

• To investigate the relationship between EAI injection duration and the amount of epinephrine absorbed into muscle tissue.
• To determine if longer EAI contact times improve epinephrine delivery and absorption.
• To provide evidence-based recommendations for EAI usage duration.

Main Methods:

• Utilized 21 epinephrine autoinjector (EAI) devices (0.3 mL) for injections into marbleized beef across seven distinct time intervals.
• Employed a digital scale to precisely measure pre- and post-injection weights of both EAIs and beef.
• Calculated epinephrine release and absorption by analyzing weight differences, simulating muscle tissue uptake.

Main Results:

• No significant linear correlation was found between injection duration and the amount of epinephrine released or absorbed (r=0.321, P=.48).
• Over 95.9% of the epinephrine dose was absorbed into the simulated muscle tissue at all tested intervals.
• Absorption percentages showed no significant difference across time periods compared to a 10-second interval (ANOVA P=.16).

Conclusions:

• The study demonstrated no linear relationship between the duration of EAI use and the amount of epinephrine injected or absorbed.
• Findings suggest that holding an EAI in place for 1 second is as effective as holding it for 10 seconds for epinephrine delivery.
• These results may inform improved patient education and EAI usage guidelines to ensure effective anaphylaxis treatment.