Naltrexone is a pure opiate antagonist and, as such, is not considered a substitution medication for an agonist. However, it has recently received considerable attention when used for "ultra-rapid" detoxification under general anaesthesia. In addition to its use as a rapid detoxification agent, naltrexone has also been utilised for decades as a longer-term "blocking agent" in maintenance treatment.
A Cochrane review on the effectiveness of naltrexone maintenance treatment did not find evidence for its effectiveness in maintenance therapy, however. A trend in favour of treatment with naltrexone was observed for certain target groups (particularly people who are highly motivated), as has been previously described in the literature (Kirchmayer, 2003).