As a followup--I found that the R version seemed perhaps a bit too potent over time? I had a reaction to it after awhile and so now vary usage between the two versions with some intermittent periods of non-use. Not sure why I reacted--I asked the neurologist and she thought it could be a reaction to something from the gel caps or other component used in making them. So I have tried different brands, too. If you have problems with it then try different brands including non R-brands and see what works for you.