I've known many users over the years, many OD while others decay over a few years. One customer in particular used ketamine heavily. Due to a string of poor de

I've known many users over the years, many OD while others decay over a few years. One customer in particular used ketamine heavily. Due to a string of poor decisions, he was on federal probation and subjected to random drug tests. He determined two drugs were not detectible by the tests at that time: ketamine and GHB. And he frequently consumed them. I remember him stumbling around my store, sipping caps of G every so often... sniffling behind tall pallets to suck up another key bump. Over a year or so, he developed severe problems with his bladder, but wouldn't / couldn't stop his drug use, even after I broke it down to him plainly; "Bro, you are killing yourself." From what I can tell, users don't keep track of doses, or much of anything. Their objectives are short term in nature: get high asap. I suspect any such article that provides hard numbers like what you want will provide guestimates at best.