Well fentinol is already in the cocaine supply, so why not this stuff that makes the user not respond to narcan. If you take a look at that drug checking website (someone here on poal posted it) pretty much every street drug, including meth and weed, has fentanyl in it. This increases the likelihood that someone will OD. Now if they add this stuff, the user will be more likely to die with no response to the narcan.