Anne, I don't know if this any help or not, but I'll offer my input.
What I would do is cut it down. You can buy 50 mg ALA capsules, and try cutting them down by eighths, or 6.25 mg. If I had to, I would even cut down by tenths, or 5 mg.
It is unfortunate that ALA is marketed in such large dosages to begin with.
When you get down to a tolerable level, stick with it a little while and see if you are getting substantive improvements.