Hi MH,
High-dose B vitamins are easy to get, no prescription required as Gerard said. They are easily bought from places like pharmacists, GNC or Holland & Barrett.
I found these at GNC :
http://www.gnc.co.uk/high-potency-supre ... ets-2.html
And these at H & B :
http://www.hollandandbarrett.com/pages/ ... prodid=196
As to your question about whether B vitamins will improve your PAWS symptoms I'm afraid I can only fudge an answer to that.
If you are nutritionally healthy, with no deficiencies in vitamins or minerals, then it makes sense that everything in your life related to health will be improved and that includes PAWS symptoms. However, I think that any organisation (and that includes hospitals) that helps people through detox will always dose up alcoholics with high doses of Vitamin B Complex, thiamine and Vitamin C, and will expect those people to continue taking those pills for between 3 and 12 months. If you are positive that you have fixed all nutritional deficiencies that you may have had then obviously taking supplements is a waste of time and money. If you are in any doubt then buy the pills and take them. If you take the pills and then feel better you will never know whether the improvement would have taken place anyway. Sorry I can't be more helpful.
If you do some google searches for "nutrition for recovering alcoholics" or similar search terms you find pages where people are passionately pro-supplements and other pages where people are totally the opposite. I'm with the pro-supplements group - bet you would never have guessed.

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