The evidence that acupuncture helps with withdrawal symptoms is tantalizing but insufficient, and it probably doesn't help prevent relapses at all. But given the dearth of successful medical treatments for addiction, there clearly needs to be more research into the role of acupuncture detoxification as part of a comprehensive treatment program.

An excellent review of studies of acupuncture and substance abuse was written by Brewington, Smith and Lipton, the first two of whom work at Lincoln Hospital in the Bronx, where the use of acupuncture in treating withdrawal symptoms of drug addiction was pioneered. If you're interested in a comprehensive analysis of both published and unpublished trials, see this review.