It's not even 'building' one, it is literally just buying a commercially available FDA approved autoinjector and a vial of epinephrine to load into it.
It is really strange that the FDA is totally fine with diabetics buying vials of insulin and loading their own autoinjectors, but doing the same thing with epinephrine is apparently extremely dangerous and the FDA doesn't want you to do it[1].
This is a devil's advocate argument, but the difference is between one person who routinely uses the drug versus another who may go for years before needing to use it in an emergency situation.
The EpiPen is designed to be used with minimal training. A diabetic who injects themselves regularly with insulin is presumed to have the skill to do it without screwing it up.
The person using it (performing the injection) doesn't need any more training than an epipen, they are basically the same in that regard. You take off the cap, push it against the skin, and press a button. The slightly tricky part is loading the injector which would presumably be done by the patient well ahead of it actually being used.
Epi is a drug that is a vascodialator in large muscles and a vascoconstrictor in small muscles.
If you inject the right amount of insulin in the wrong place, not much happens. If you inject the right amount of epi in the wrong place like a finger, you could lose that finger.
You could argue a diabetic’s ability to administer during an event is just as bad someone in anaphylaxis all day long... one is passed out and the other is panicking because they are dying...
But epipen’s unique injector is primarily to get the right amount in the right place. Two part problem it solves over the vial.
I bet more people have died because there was no pen present (too expensive) than would have died from incorrect administration of a cheaper pen. So the design of the epipen solves a problem, but are we making the right tradeoff in insisting on using that solution at a high price point?
This is like the fact that TSA searches make another 9/11 less likely, however people driving instead of flying to avoid the hassle is estimated to have killed more people than 9/11 itself did. Risk is a funny thing, and isn't always straightforward to figure out.
Making it personal, in theory my daughter should have 2 epipens close at all times because if she gets stung on the neck, she could need one. Anywhere else is OK, the concern is swelling from her allergy cutting off airflow. That explains one, and the second is in case the first fails to work properly, which sometimes happens.
In practice there is an epipen for her at school, and at her mother's house, but not at my house. We shelled out once. But we're not shelling out over and over again to prevent such an unlikely disaster. (Twice more so that there are the recommended number of pens at school and both places she lives, then more as we lose them since they are supposed to always be on us..soon we're talking about real money!)
So... you can can get checked out on and get a script for the vile of epi. Adjusts typically get .3mg and kids .15mg iirc. For the normal 1mg/mL stuff... and that’s for anaphylaxis of course, not a heart attack.
That’s cheap and pretty easy to do. The problem is while maybe I’m a superstar with a vile on someone else, I wouldn’t trust I could do it while my throat was literally closing, in all scenarios. The pen makes sense a lot of time, but the vile is good if you know you won’t be the target.
Something you wrote also, 2 pens. If you need one, there is a good chance you’ll need two. Depends on how fast you can get to a hospital and the circumstances with the victim.
So in that case, the vile makes even more sense for you to have at home.
Diabetics don't tend to take insulin in a panic. If they are panicking, it's because they are already low, and need glucose (which can be administered in an injectable form, and is usually only used if the diabetic cannot be woken).
In my example the diabetic was passed out. Or like the with diabetics I've had to deal with, stubborn mule-like insistence they're fine! It's the people going into anaphylaxis that I think panic, for pretty good reason.
But it's just an example. My point was more that insulin is generally safer than epinephrine.
See https://spectrum.ieee.org/the-human-os/biomedical/devices/ha....