I took way to much DMSA at first and had rapid heart rate, severe headache and sweating. After dropping the dose for several months I can tolerate it now at that origional dose.
Start out with a very low dose and don't add ALA for at least several months. You have to take the DMSA every 4 hours even at night or you make matters worse.
After several months, I have switched to Liposomal DMSA which releases slowly over 48 hours, It also goes where regular DMSA can't, but it is not well studied and may not be prudent early on when you have a heavy body burden of mercury. I also now use time release ALA and seem to be doing just fine on both. Animal studies have shown Liposomal DMSA more effective than regular, but like I said, it might not be a good bet early in your chelation.