Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Retention in treatment
[33] Systematic review	725 people 6 RCTs in this analysis	Proportion of people who completed outpatient treatment 233/406 (57%) with buprenorphine 137/319 (43%) with clonidine	RR 1.45 95% CI 1.12 to 1.88 P = 0.005	Small effect size	buprenorphine
[33] Systematic review	481 people 5 RCTs in this analysis	Proportion of people who completed inpatient treatment 208/260 (80%) with buprenorphine 94/221 (43%) with clonidine	RR 1.93 95% CI 1.27 to 2.92 P = 0.002	Small effect size	buprenorphine
[32] Systematic review	829 people 8 RCTs in this analysis	Proportion of people who completed treatment 344/424 (81%) with buprenorphine 169/405 (42%) with clonidine	OR 2.22 95% CI 1.10 to 4.26	Moderate effect size	buprenorphine