Guo 2001.

Methods	randomised placebo controlled trial; used the table of random number. ratio of patients receiving naltrexone to those receiving placebo: 2:1 double blind. Multicenter study.
Participants	49 Chinese patients who completed detoxification without using opiates for at least 5‐7 days before naltrexone treatment. Mean age: 24,96 (naltrexone) 26,76 (placebo). Male: 88,57% (naltrexone),92,86% (placebo). Educational level below junior high school: 68% (naltrexone) 78,57% (placebo); unemployed : 57,14% (naltrexone) 35,71% (placebo)
Interventions	naltrexone 50 mg/day(35) vs placebo (14). Outpatients setting duration: 6 month study
Outcomes	use of substance of abuse: n. of patients abstinent every month and at the end of the study. adverse effects
Notes	withdrawn from the study: data not given. Results on use of substances presented for 34 patients on naltrexone and 12 participants on placebo
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk	quote: " the randomisation was performed according to the tables of random permutation"
Allocation concealment?	Unclear risk	method for allocation concealment not reported
Blinding? objective outcomes	Low risk	the study is labelled as double blind, but is also reported that " to investigate the optimal dose for Chinese patients, naltrexone was titrated according to the patients response COMMENT:The lack of blinding is unlikely to bias objective outcomes
Blinding? subjective outcomes	Unclear risk	the study is labelled as double blind, but is also reported that " to investigate the optimal dose for Chinese patients, naltrexone was titrated according to the patients response
Incomplete outcome data addressed? All outcomes	High risk	not reported how many patients dropped out form the studies and the different outcomes are measured on different numbers of patients