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Epinephrine Auto-Injector Teardown

For millions of people around the world, having an Epinephrine auto-injector can mean the difference between life and death. According to the National Institutes of Health (NIH), the Epinephrine injection is used along with emergency medical treatment to treat life-threatening allergic reactions caused by insect bites or stings, foods, medications, latex, and other causes. Epinephrine is in a class of medications called alpha- and beta-adrenergic agonists (sympathomimetic agents). It works by relaxing the muscles in the airways and tightening the blood vessels.

According to,  2.45 billion of these syringe units were sold in 2011 with an expected  3.59 billion to be sold in 2015. Pre-filled syringes form one of the fastest growing markets in healthcare.The devices contain a spring-loaded needle that exits the tip of the device (in some cases through a sterile membrane) and penetrates the recipient’s skin, to deliver the medication via intramuscular injection.

To show you how these incredible devices work, we did the teardown of one of the most Epinephrine Auto-Injectors in the market, the Epipen®. As you can see in the following x-ray image, there are 5 key parts of this auto-injector. Let’s start from the top of the Epipen® (5), which is the actuator (or button) you press to trigger the pen. This trigger releases a powerful spring (4) that can apply several pounds of force to release the medication inside the syringe (3). This force also causes the needle (2) to exit the auto-injector and penetrate the patient’s skin. To absorb some of that impact, the release spring (1) takes some of that shock to provide the patient with a smooth experience (similar to the shock absorbers in your car).


There’s a lot of information on this topic online. We found the Mayo Clinic website specially useful.



EpiPen® is a registered trademark owned by the Mylan companies
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