“…All the studies conducted either semistructured or open-ended interviews, focus groups or observation to collect data. Six studies assessed methadone and/or buprenorphine detoxification and/or maintenance programmes (Larney et al, 2017, Rubinstein et al, 2017, Perkins and Sprang, 2013, Johnstone et al, 2011, Stöver et al, 2006, Asher, 2013, while the remaining studies reviewed methadone maintenance programmes alone. Only four studies were conducted in LMIC countries (Kyrgyzstan, Indonesia and Iran) (Rhodes et al, 2019, Culbert et al, 2015, Moradi et al, 2015, Zamani et al, 2010.…”