BACKGROUND:Retention in opioid substitution (OST) treatment is associated with substantial reductions in all cause and overdose mortality. This systematic review aims to identify both protective factors supporting retention in OST. and risk factors for treatment dropout. METHODS:A systematic search was performed using MEDLINE. https://www.nacrack.com/hot-savings-HiBoost-Home-15K-Smart-Link-F20G-5S-IoT-limited-super/