Friday, November 18, 2016
The sessions at the Food Allergy Bloggers Conference (FABLogCon) are always terrific. There are two tracks and sometimes difficult choices have to be made. This year I made it a priority to hear Dr. Julie Brown talk about epinephrine and auto-injectors (a session that I missed at FABLogCon 2015).
I learned that it's not just size and form of the auto-injector that matter:
1. Dosage is less scientific than I thought. Epinephrine auto-injectors come in two standard sizes/dosages – the adult version (containing 0.3 mg of epinephrine) and the junior/child version (containing 0.15 mg of epinephrine), for children weighing less than 66 pounds. We have been taught to always carry two epinephrine auto-injectors, as in some cases a second dose is needed. However, we don’t really know what the “best” dosage is. The very simple reason for that is that doctors can only study the data based on what has happened in the past. (No, we really don’t want to be forcing anaphylaxis in humans to study the drug.) Unlike medications for hypertension, for example, the correct epinephrine dose for each patient cannot be found by prescribing a dose, testing, and modifying. Nevertheless, with epinephrine the two-sizes-fits-all approach seems to work well.
2. The size of the needle matters. I never really paid attention to the length of the needle (it is hidden in the auto-injector, after all). But the needle length is designed so that the drug can be injected into the muscle. If the needle goes too far, it hits bone. If the needle doesn’t go far enough it can’t reach the muscle. (Remember that the auto-injector should be placed against the meaty part of the outer thigh.) The adult versions of auto-injectors have slightly longer needles than the kids’ versions. But depending on how much muscle and how much fat you have (yeah, I mean weight) – can affect where the needle lands. The key here is to get it into the muscle. In very lean patients it may be necessary to bunch up the skin before injecting to avoid hitting bone.
3. There is a good reason the instructions for epinephrine auto-injectors have changed. For years we were told to hold the auto-injector against the thigh and count to ten. Ten seconds has been reduced to three. Once the drug is released, there is no reason to hold just for the sake of holding… and holding too long can result in serious injury. Dr. Brown showed us photos of lacerated thighs and thighs with scars from injection accidents where the patient moved quickly or the needle was inserted into the thigh a second time because the person administering the dose wasn’t sure it was complete.
4. The type of needle also matters. Dr. Brown showed us video of a variety of “traditional” pen-like auto-injectors (e.g., Mylan’s Epi-pen and Impax’s Adrenaclick) and we could see the needle going into the lab-fashioned “thigh” (no human subjects were used in this simulation), with the drug being released in about 2 seconds. With these traditional devices, the needle is pulled out of the thigh (and then covered with a cap until it can be disposed of properly). Most revealing to me was the video of the Auvi-Q auto-injector; in this case the needle goes in more quickly, releases the drug more quickly and then retracts – this all happens in what appeared to be an instant. Dr. Brown didn’t have to say anything more to make it clear that the retractable needle is more efficient and safer (avoiding the lacerations noted above). It turns out there is a whole lot more to auto-injectors than meets the eye.
Notes: Epi-Pen and Adrenaclick are currently available on the market. Kaleo Pharma plans to bring the Auvi-Q back to the market in the first half of 2017. Pictured above is the training device for the Auvi-Q.