The papers I've read seem to mainly lay the blame with drugs that have a keto group on the cyclohexyl ring. In the original interview with HM, I stated that I was trying for a MORE bladder friendly dissociative, for treating phantom limb pain (by the way, the reference - think it's no 5 - that states mxe was originally made as an antidepressant is so fucking incorrect, I'm amazed it became a ref. It's original raison d'etre was as a dissociative to treat phantom limb pain. That such a piece of disinformation is now accepted as a ref makes me a bit hesitant regarding other references).
The Chinese paper was giving rats 30mg/kg per day. That is, without the per kg bit, a human dose. Humans tend to be at least 50x the weight of rats, implying the equivalent human dose would be min 1500mg per day. That is a fucking huge dose. This iswhere the more bladder friendly comment becones relevant. No drug is totally safe (shit you can die from water intoxication).
As one final comment, results with one species are not a generalized response. Rats can eat MPTP until it's coming out of their ears and show no signs of Parkinson's disease: it only has that effect on primates.
In terms of goals, mxe is a lot less urotoxic than ketamine and is generally less disturbing than ket. Those were the original goals, which I feel it achieved. If I'd had a full research lab, with adequate funding, I feel results could have been much better (without it's amazing antidepressant properties being taken into account). As I've said elsewhere, if you have a narrow result you're aiming at, things can be massaged to give the results wanted. MXE causing bladder damage in previous heavy ketamine users - well it's less damaging than ket - who knows how much damage had been caused by previous ket use and the pureMXE study, in rats utilized frankly ridiculous daily doses.
MXE is far, far from perfect, but I do feel there was a concerted effort by 'research' to overly demonize MXE, for 'war on drugs' purposes. I mean, one scruffy hippie creating a drug that surpasses the usually used dissociative makes governments/big pharma appear crap, and we can't have that, can we?