A 28-year-old man is intoxicated from opioid abuse on entering county lockup. He presents stuporous with pinpoint pupils. About 24 hours later, he is in withdrawal and becomes highly agitated while yelling and complaining of being cold. Although detoxication from opiates is generally safe, it is highly unpleasant and, alone, is not likely to represent a complete strategy for treatment of opioid-addicted patients. What percentage of opioid-addicted patients relapse 12 months after undergoing successful detoxication