Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Retention in treatment
[37] Systematic review	311 people 3 RCTs in this analysis	Length of time in treatment with alpha2-adrenoceptor agonist with tapered methadone Absolute results not reported	SMD –1.07 95% CI –1.31 to –0.83 Meta-analysis limited by diversity in study design and in assessment and reporting of outcomes	Effect size not calculated	methadone
[37] Systematic review	399 people 5 RCTs in this analysis	Proportion retained in treatment 104/192 (54%) with alpha2-adrenoceptor agonists 135/207 (65%) with tapered methadone	RR 0.81 95% CI 0.64 to 1.04 Meta-analysis limited by diversity in study design and in assessment and reporting of outcomes Heterogeneity: P = 0.03		Not significant
[36] Systematic review	577 people 7 RCTs in this analysis	Proportion of people completing treatment 168/251 (67%) with tapered methadone 192/326 (59%) with alpha2-adrenoceptor agonists	RR 1.10 95% CI 0.90 to 1.32 P = 0.34 Significant heterogeneity: P = 0.01		Not significant