I was/am(now on bupe) a serious junkie.
Not attractive at all. Fentanyl sucks anyway, it's not all about potency.
Now, going to the paramedics after they wind up carting away a blue corpse and asking what the stamp was, well, that I can understand.
Carfentanil, no.
Also, why the 'i' (or why the 'f' in lys-dexamfetamine), neither. Different languages may spell things differently but there's supposed to be some uniformity, even if it will sound the same, in the way drugs are officially called in one language or at least in one pharmacopoeia.