As I understand it, paracetamol was discovered as the active metabolite of a much more damaging drug (acetanilide); and that most of paracetamol's effects is due to a metabolite of paracetamol in turn, namely AM404.

Why the pharmaceutical companies haven't done to paracetamol what they did to acetanilide, I don't understand. Providing AM404 directly would avoid the production of NAPQI in the body.