This past summer, pharmaceutical scandal erupted over the skyrocketing price of EpiPens, epinephrine auto-injectors used to treat anaphylactic shock. The devices are now sold as a two-pack for $600 when they were sold for $57 dollars each in 2007 before Mylan Pharmaceuticals purchased the rights to EpiPen. Despite the congressional hearing last month, there has yet to be anything done to effectively bring the price down for people who need these life-saving devices. There has, however, been some investigation into how EpiPens actually work and even attempts to make them at home for much cheaper.
The EpiPen works via a spring loaded mechanism. The EpiPen has two springs: the spring around the plunger and the spring that pushes out the needle sheath. Both are compressed until a person presses the EpiPen against their thigh. This leads to the springs being released which projects a needle that breaks the skin’s surface so that the dose of epinephrine may exit the EpiPen.
The larger spring that provided the power for the injection had a calculated spring constant of 8.65 lbs/in. This is 0.977 N/m. That spring is 3 inches long and we will assume that it is compressed to half its size, so 1.5 inches or 0.0381 m. That means that the PE stored in the spring = .5(0.977 N/m) (-0.0381m)2 or 0.00071 J. Not all that much to save a life!