I gave up using DMSA on patients years ago with mercury toxicity, I found that it affected the digestive system too many times with an incredible amount of folks.
Dr. David Quigg from Doctor's Data, and expert in heavy metal chelation, said to me once that it has the propensity for causing plenty of adverse in a patient, and like DMPS, one needs to go REAL easy.
Dimercaptosuccinic acid (DMSA), is the organosulfur compound that can make a lot of folks feel really stink, I have seen it create waves of nausea, vomiting, diarrhea and many other side-effects, which the patient will feel is "mercury being released from the body". Most symptoms are liver based, and I have seen a few patienst actually hopitalized after this form of treatment over the years.
Most folks haven't figured out that a treatment as strong as DMSA can create many liver and gut symptoms in its own right, which are NOT associated with the release of Hg, but are liver-based aggravations.
I'll stick with cell fractionated chlorella and cilantro extracts, I don't seem to get the aggravations with patients that I used to get with chemically produced sulfur based compounds.
The body releases heavy metals in "chunks", and at times for no real clear cut reason, and this is why I gave up on "provocation tests" as well years ago. I'm over "paralysis from analysis" in my clinic, and prefer the patient invest their hard earned cash on treatment instead of lots of routine tests which stick cash into the pocket of the doc. Patients either get well over time, or stay unwell, and I don't find that tests seem to speed their improvements up.
The best results I now appear to get after using all manner of heavy metal chelations the past 25 years in my clinic is the slow and gentle way.