When a person is going through alcohol withdrawal, the most important vitamins are thiamine and folic acid. If an alcoholic who stops drinking does not have enough of these vitamins, they can get Wernicke syndrome, a very serious brain problem. To keep this from happening, people who have stopped drinking alcohol are often given thiamine and folic acid intravenously (through a needle placed into a vein). They may also be given other vitamins. This can help prevent Wernicke syndrome.