Hello,
There has always been talk of Pantothenic Acid (B5) and its long-term effects at high doses. Wanting to try B5 myself, did some "research" and found a very detailed report.
In any case, a 2003 report by the Food Standards Agency (it's 360 pages, but of course not all relevant) on maximum doses details the few studies done at different dosages of primarily 2,000mg and 10,000mg. There are about six pages of info specific to B5.
I outline some results here, but please read the report and don't take my word for it, since of course we can all easily make mistakes!
There is a possibility that liver damage could result from long term exposure to high doses of B5, although it is quite possible--according to the report--that that result was due to another substance in the capsules, since more than one were being studied in that specific trial.
All other trials showed no adverse effects after several months, with a 2000mg or 10000mg dose per day, in humans, dogs, and monkeys.
Bottom line is that they could not establish a maximum upper boundary for humans, and so did not publish one. They have not found any varifiable negative effects on larger doses over several months.
They believe that about 200mg should be easily tolerated on a long term basis by most humans, and that is their only firm conclusion.
One final detail: it is pretty certain that every person gets sufficient B5, and that B5 deficiency really doesn't exist for anyone, with rare exceptions. So, after reading this I am beginning to suspect that B5 deficiency cannot be a cause of acne, as claimed by so many places. Rather, it's "deficiency" from the high doses
Also, it seems strange that we'd need on the order of grams of a vitamin, per day. That is a lot.
So, that's good news, eh?
I for one will start trying B5 to see if it helps!
Please see the report for further details, that's what you really need to get a clearer picture. It's freely available on the web. Here is one address:
[url]http://www.foodstandards.gov.uk/news/pressreleases/vitsandminspress[/url]
The link is at the bottom of the page: "Safe upper levels for vitamins and minerals"
It is 1.37Mb.
Safe B5 levels (study details included) 
