The newest use for magnesium is as an IV drip in severe asthma. I have never used it (partialy because my old dog brain can never remember that we can do this now), but every medic I know who has used it swears by it. I think if I had had this experience, I would likely list Magnesium higher.
An ED doctor told me once, Epi stops the reaction and Benadryl cleans it up. So while Benadryl is a great drug for allergic reactions, it is not the ultimate life-saver epi is….Still I would hate to not have Benadryl in my kit.
I rate it above calcium partly because it links me more closely with Johnny and Roy, and more importantly because it can be used for tricycliate overdose, and for crush injuries (I have never used it for these indications).
I don’t use calcium very much, but there is one situation I always reach for it in — cardiac arrest in a diaylsis patient. While we don’t have labs in the field, a dialysis patient is a possible bet to be hypocalcemic and/or hyperkalemic, and calcium can save lives if they are.