Nicotine dependency is treated by administration of an opioid antagonist. In some embodiments, rapid or ultra rapid detoxification techniques include using a combination of an effective amount of an opioid antagonist such as nalmefene, naloxone or naltrexone or a mixture of any one of these, and either clonidine or related compounds either while awake, or while under sedation or anesthesia, followed by continued administration of an effective amount of an opioid antagonist with or without agents that enhance nicotine dependency treatment. Persons are also treated for nicotine dependency with more gradual detoxification methods using administration of a combination of an effective amount of an opioid antagonist such as nalmefene, naloxone, naltrexone, or a mixture of any of these, and an effective amount of agents used to treat nicotine withdrawal including nicotine, such as that delivered by a nicotine patch, nicotine chewing gum, nicotine inhaler or other methods for delivering nicotine, antidepressants and antianxiety agents, and/or clonidine and related compounds. Administration of an effective amount of an opioid antagonist to prevent relapse, attenuate craving, and reduce weight gain during and after treatment for nicotine dependency is continued in some embodiments.