Naltrexone is used to maintain abstinence following opioid withdrawal in addicts.It blocks all of the following features of opioid use, except:

Naltrexone, is a medication primarily used to manage alcohol or opioid dependence. An opioid-dependent person should not receive naltrexone before detoxification. It is taken by mouth or by injection into a muscle. Effects begin within 30 minutes. Ref: KD tripathi 8th ed.