I don't know why he was taking Niacin - but this is a theory - I have read alot of literature about how people take large doses of Niacin to clean their systems out. They do it pass drug screenings, and they also do it in an attempt at lowering their tolerance.... Niacin basically has the effect of burning chemical and other residue from your system, if you take a large dose of it - You become very red and flushed, and sweat like crazy for several hours - but apparently it 'cleans' your system. Wonder if he was trying to lower his tolerance to the opioids? I have seen where people use large amounts of Niacin for this reason?