My neurologist prescribed 600 mg per day but didn't mention the R version. I discovered that by doing research. This version helps stabilize ALA as it can be made less effective easily. Also discovered that you should take it 30 minutes before eating or 2 hours after or it will also interact with food and the effects will be lessened. I used it for 6 months then decided to go off it. After a month where my symptoms worsened I have gone back on it. Hopefully it will help again. I have used the R version from Vegan Labs