Sustained release technologies for administering the
opioid antagonist naltrexone (SRX) have the potential to assist
opioid-addicted patients in their efforts to maintain abstinence from
heroin and other
opioid agonists. Recently, reliable SRX formulations in intramuscular or implantable
polymers that release
naltrexone for 1-7 months have become available for clinical use and research. This qualitative review of the literature provides an overview of the technologies currently available for SRX and their effectiveness in reducing
opioid use and other relevant outcomes. The majority of studies indicate that SRX is effective in reducing
heroin use, and the most frequently studied SRX formulations have acceptable adverse events profiles. Registry data indicate a protective effect of SRX on mortality and morbidity. In some studies, SRX also seems to affect other outcomes, such as concomitant
substance use, vocational training attendance, needle use, and risk behaviour for
blood-borne diseases such as
hepatitis or human immunodeficiency virus. There is a general need for more controlled studies, in particular to compare SRX with agonist maintenance treatment, to study combinations of SRX with behavioural interventions, and to study at-risk groups such as prison inmates or
opioid-addicted pregnant patients. The literature suggests that sustained release
naltrexone is a feasible, safe and effective option for assisting abstinence efforts in
opioid addiction.