BlueDahliasBrother said: "I thought it only crossed the blood brain barrier when injected."

It might be more correct to say that it might only cross the BBB in sufficient quantities when injected. When you take mannitol orally, most of the stuff gets excreted, and you can't take more than a certain amount orally or you will get diarrhea.

But we shall see (in another year or two) (maybe) ...