Opioid antagonists definition

Similarly opioid peptides are important in nicotine addiction and may have a role in causing nicotine withdrawal symptoms in some smokers [35]. Opioid antagonists such as naltrexone are licensed treatments for dependence syndromes arising from other addictive drugs and could also be of use in some smokers to aid nicotine withdrawal [59] although there is no definitive evidence overall that they are beneficial [60]. 

Development of physical dependence during the longterm administration of methadone can be demonstrated by drug withdrawal or by administration of an opioid antagonist. Subcutaneous administration of 10 to 20 mg methadone to former opioid addicts produces definite euphoria equal in duration to that caused by morphine, and its overall abuse potential is comparable with that of morphine. 

Buprenorphine 4-6 20-30 Partial agonist. Can act as antagonist in concomitant treatment with other opioid. Also available as plaster without definite advantages as concerns the method of administration. Probably lower risk of dependence... 

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