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| Disclaimer: Epinephrine is a powerful drug. It requires a physician's prescription for good reason. Giving someone epinephrine when it is not needed, or giving them too much, can cause all sorts of awful things and might kill your patient. This web page is only to give you an idea of how to take apart a run-of-the-mill Dey Labs epi-pen (the most common variety at this date, 2/07). Not all Dey Labs epipens are guaranteed to be the same as this one. If you are planning on putting yourself in a situation where you might possibly try to re-use an epipen then you must take one apart yourself to see how your own equipment works, figure out for yourself how to control the dose, be familiar with IM injection, how not to prick yourself or anyone else, etc. Technically and legally speaking, fooling around with the inside of an epi-pen is effectively filling a new prescription for a half dozen more doses of a life-saving/threatening drug- so that should give you an idea of who can legitimately re-use these. This page is a valuable resource for those folks who read in a manual somewhere that the pens can be used in dire wilderness circumstances, but I'm not responsible if you make someone's life awful or all out kill them. |
Anatomy/Re-use of an Epi-pen.
Over the last few years a lot of folks have asked me about rumors they have heard about re-using epipens. As stated on the manufacturer-provided instructions, and obvious to anyone who has used the epipen, most of the drug remains in the epipen. I have read references in wilderness medical texts to the possibility of re-using a pen, but never any instructions. If you are in a wilderness situation with only one epipen, and have a patient who is relapsing into anaphylaxis (extremely unlikely hypothetical, but anyways..), could you use that leftover epinephrine?
To satisfy my own curiosity, I shot off an expired pen and then took it apart. I include photos and descriptions here in case you are curious too. It turns out it is pretty doable to take the pen apart, and then use the included parts to re-configure it as a preloaded IM syringe.
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The first step is to cut the pen open. The best place to do this is near the end (where the safety cap came off). Cut into the pen body, working around the circumference. The plastic isn't that hard to cut. A swiss army knife saw would work fine. A serrated knife would work slowly. A sharp un-serrated knife would work too, spinning the pen while slowly grooving it with the blade, but a saw of any sort would be easier. By cutting into the end, there is nothing important to cut into if you go too deep, just a plastic sleeve inside that isn't useful. Just be careful when you think you are almost done with the full cut. The strong spring inside is still cocked and the end will shoot off with some force if you finish the cut and aren't holding onto it. Obviously, if you want to re-use the epipen's needle, you will need to protect it from damage and keep it clean.
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Once you have opened the pen up, slip the inner cylinder out.
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Then pull the syringe assembly out of the inner cylinder.
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note: epinephrine is clear when it is still good. |
Above: you can see the vital bits and pieces. The collapsed rubber thing is what keeps the needle sterile between the factory and the leg. The needle is swaged onto the glass syringe body, which has a rubber seal (black), a plunger-stop (white), and the plunger/release (metal thing at the back). When you push the epipen against the leg, the outer cylinder slides over the inner cylinder, putting pressure on the plunger/release at the back. If the safety cap is off, you will push hard enough that the prongs at the back of the release are forced through a metal washer. The spring then fires, shoving the plunger forward, pushing the needle through the seal and into the leg, and then injecting the drug. When the correct dose has been administered the plunger-stop flange will seat against the glass syringe stopping any further drug from being administered.
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First step to taking the thing apart is to take the plunger-stop/release out. The white plunger-stop is screwed into the black seal. Grab the plunger and unthread it (left-loosey!). Then wiggle the plunger/release (the pronged metal thing) until it pulls out of the white plunger-stop. You should also pull the rubber needle cover off the end of the needle, and put it in a clean spot (or you could straighten it out and pull it back over the needle to protect it).
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the white plunger-stop is at the side. |
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note: i have replaced the old epinephrine with water. |
Now you can use the plunger/release pronged-thing as a new plunger. Leave the white plunger-stop out, and insert the release backwards. Conveniently, the prongs fit nicely over the seal threads. You could now administer the remaining epinephrine.
This would be a great time to have a think about the dose. An adult epipen administers 0.3ml (epipens are loaded with 1:1000 concentration; one mg per ml). An epipen junior administers 0.15ml. This pen is an adult pen, and there are 5 or 6 doses left. Give someone that much and they will be very unhappy with their patient care...
| Meta Disclaimer: If I told you that you could make a parachute out of four airline blankets, a hair pin, and some dental floss, and leap from a 737 at 30,000 feet and survive with only two broken legs, would you try it? Would you strap the contraption to your buddy and push him out the door? You probably wouldn't. For many reasons, it would be a bad idea. Likewise, for many reasons, taking apart an epi-pen could be a bad idea. For goodness sakes, Don't be stupid!! |
I emptied out the syringe and used a graduated syringe to get an idea of what an adult dose would be (ie: how far to depress the improvised plunger). By my calculations, I would need to depress the plunger just under 5mm (4.8 mm, but its hard to be exact with my equipment) to administer a standard 0.3ml adult dose. This calculation relies on all glass syringe bodies being the same diameter. I have no idea if all epipens are the same in this dimension. I also could have screwed up the calculation. YOU MUST USE YOUR OWN DISCRETION. IF YOU SCREW THIS UP, YOU COULD KILL SOMEONE. If you are qualified to be diddling around with this sort of project, you probably can think of a decent way to estimate doses or work around the problem.
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If you administer your epipen, and then want to be prepared in case your patient relapses, you could go ahead and take it apart. Clearly, this process is not something you want to do while your patient is in a bad spot. If you think you might want to re-use a pen, give them some benadryl and then go ahead and get it ready. If everything is staying stable, but you want to keep the new setup together just in case, I would pack it up as pictured above. Straighten out the rubber needle cover and slip it back over the needle to keep it clean and protected. remove the plunger, and screw the plunger-stop back onto the seal to stop it being inadvertently squirted. then put everything back together, except leave the spring out. you can put a bit of tape to hold the two sections together. Obviously, this is no longer a sterile device, and who knows how long the drug will be ok for, but its better than nothing. Time to leave the woods and throw the epipen bits out.
If I have made a mistake somewhere, or if you have a suggestion or an addition, see my email address on the contact page of electricant.net
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