Polish, American and Japanese scientists all independently pioneered Epinephrine from 1895 to 1896 with extracting it from adrenalin.
In the 1970s, auto injectors were developed for the military for treatment of the effects of chemical warfare.
Sheldon Kaplan first invented the Combo Pen, an auto-injector filled with nerve gas antidote, for the U.S military in the 1970s. He never collected a penny in royalties.