I thought of Krokodil also. Considering that tiny amounts of impurities can cause terrible consequences. MPTP impurities in MPPP caused parkinson's, and bad commercial synthesis of tryptophan by Showa Denko caused EMS, it seems likely that this is real.
I thought of that drug as well. The thing I remember most about that is if the addict missed the vein and injected it into the tissue, it would basically destroy the area. Addiction to drugs like this is horrible way to end one's life.
https://en.wikipedia.org/wiki/MPTP https://en.wikipedia.org/wiki/Tryptophan