If a person abstains from opiate drugs, then therapy with naltrexone can be started in prisons or prior to release from prison. Naltrexone is a pure opiate antagonist and, as such, is not considered a substitution medication agonist. However, it has recently received considerable attention when used for ultrarapid detoxification under general anaesthesia a practice that is not without risk to the patient. In addition to its use as a rapid detoxification agent, Naltrexone has also been used for decades as a longer-term blocking agent (full opiate antagonist) in maintenance treatment.

The opioid antagonist naltrexone may be used as part of relapse prevention programmes. A single maintenance dose of naltrexone binds to opioid receptor sites in the brain and blocks the effects of any opioid taken for the next 24 hours or can be taken in a double/triple dose three times a week. It produces no euphoria, tolerance or dependence. Patients generally require 5-10 days of abstinence before induction onto naltrexone (the length of time abstinent is dependent upon the length of half-life of the opioid that was regularly taken prior to starting naltrexone).

The effectiveness of naltrexone treatment clearly hinges on compliance with treatment, active psychosocial support, and the motivation to take the medication each day or every second day.
In summary the data does support this treatment approach for those who are highly motivated and when used in conjunction with various psychosocial therapies.

For more detailed information on clinical guidance for pharmacological treatment of opioid dependence (including in prison), please make reference to the WHO publication “Guidelines for the Psychosocially Assisted Pharmacological Treatment of Opioid Dependence”, 2009, available at

This publication cover items such as:

  • patient guidance for clinicians
  • choice of treatment approach
  • dosage of substances
  • initiation and maintenance criteria, etc.
I - Introduction
II - What is medication-assisted treatment (MAT) of opioid dependence? Part I
III - What is medication-assisted treatment (MAT) of opioid dependence? Part II
IV - Medication-assisted treatment (MAT) of opioid dependence in prisons
V - Some basic information about medication-assisted treatment (MAT)
VI - Medical ethics aspects of MAT programmes in prisons