Table 1 Characteristics of included studies

Ahmadi

2003A

Iran

Randomized controlled trial

Double blind

Duration: 18 weeks

N = 164

Mean age: 31.4 years old Buprenorphine, 33.7 years old Methadone

Male: 100%

Opioid Dependence (DSM-IV criteria)

(1) Buprenorphine 1 mg/day

(2) Buprenorphine 3 mg/day

(3) Buprenorphine 8 mg/day

(4) Methadone 30 mg/day

Retention as measured by completion rates

Ahmadi 2003B

Iran

Randomized controlled trial

Open label

Duration: 24 weeks

N = 204

Mean age: 31.2 years old

Male: 100%

Opioid Dependence (DSM-IV criteria)

(1) Methadone 50 mg/day

(2) Buprenorphine 5 mg/day

Retention as measured by completion rates

Eder, 1998

Austria

Randomized controlled trial

Open-label

Duration: 24 weeks

N = 34

Mean age: 26.35 years old

Sex not specified

Opioid dependence (criteria not specified)

(1) Buprenorphine 7.3 ± 1.8 mg

(2) Methadone 65.6 mg ± 26.6 mg

Retention as measured by dropout rates/completion of study phase

Abstinence from opioids

Toxicology Urine Samples

Gerra, 2004

Italy

Observational, non-randomized study

Duration: 12 weeks

N = 154

Mean age: 32.5 years old

Male: 74.7%

Heroin dependence (criteria not specified)

(1) Methadone 81.5 ± 35.4 mg

(2) Buprenorphine 9.2 ± 3.4 mg

Retention rate as measured using a survival analysis

Abstinence from illicit drugs

Psychiatric comorbidity

Moderate Risk

Johnson, 1992

USA

Randomized controlled trial

Double blind

Duration: 17 weeks

N = 162

Mean age: 33.4 years old Buprenorphine-8,

32.7 years old Methadone-20,

33.1 years old Methadone-60

Males: 69.8%

Opioid addiction

(1) Buprenorphine 8 mg/d

(2) Methadone 20 mg/d

(3) Methadone 60 mg/d

Retention in treatment as measured by percent of patients retained in each treatment

Urine samples negative for opioids

Failure to maintain abstinence

Kamien, 2008

USA

Randomized controlled trial

Double dummy

Duration: 17 weeks

N = 268

Mean age: 37.2 years old Buprenorphine-Naloxone-8,

38.9 years old Buprenorphine-Naloxone-16,

40.3 years old Methadone-45

38.1 years old Methadone-90

Male =

70.7% Buprenorphine-Naloxone-8, 70.7% Buprenorphine-Naloxone-16, 80.8% Methadone-45,

65.8% Methadone-90

Opioid dependence (DSM-IV criteria)

(1) Buprenorphine-naloxone 8–2 mg

(2) Buprenorphine-naloxone 16–4 mg

(3) Methadone 45 mg

(4) Methadone 90 mg

Retention in treatment as measured by weeks in treatment

Opioid abstinence

Medication compliance

Non-opioid drug use

Kosten, 1993

USA

Randomized clinical trial

Double blind

Duration: 24 weeks

N = 140

Mean age:

32 years old Methadone-35,

32 years old Methadone-65,

33 years old Buprenorphine-2,

32 years old Buprenorphine-6,

Male = 73%

Opioid dependence (DSM-III-R criteria)

(1) Methadone 35 mg

(2) Methadone 65 mg

(3) Buprenorphine 2 mg

(4) Buprenorphine 6 mg

Treatment retention as measured by weeks in treatment

Urine toxicology

Self-reported use

Withdrawal symptoms

Addiction Severity Index

Ling,1996

USA

Randomized controlled trial

Double blind

Duration: 52 weeks

N = 225

Mean age:

41.5 years old Buprenorphine-8

40.8 years old Methadone-30

40.1 years old Methadone-80

Male = 79.6%

Opioid dependence (DSM-III-R criteria)

(1) Buprenorphine 8 mg

(2) Methadone 30 mg

(3) Methadone 80 mg

Retention as measured by weeks in treatment, and as measured by percent of patients retained in each treatment

Opioid use

Opioid craving

Adverse events

Maremmani, 2007

Italy

Observational study

Duration: 52 weeks

N = 213

Mean age: 31 years old

Opioid dependence (DSM-IV criteria)

Male = 82.6%

(1) Buprenorphine 5.1 mg

(2) Methadone 61.68 mg

Retention in treatment as mesured by percent of patients retained in each treatment

Longitudinal analysis

Adverse events

Low Risk

Otiashvili, 2013

Georgia

Randomized Controlled Trial

Duration = 12 weeks

N = 80

Mean age: 33.7 years old

Opioid dependence (ICD-10 criteria)

(1) Methadone 39 ± 17.8 mg

(2) Buprenorphine (Suboxone) 8.5 ± 3.5 mg

Retention in treatment as measured by weeks in treatment, and number of patients retained in each treatment

Urine toxicology

HIV risk injection behaviours

Adverse events

Pani, 2000

Italy

Randomized Controlled Trial

Double blind

Duration = 24 weeks

N = 72

Mean age: 28 years old

Male: 86.1%

Heroin addiction of at least 2 years (DSM-IV criteria for opioid dependence)

(1) Buprenorphine 8 mg

(2) Methadone 60 mg

Retention in treatment as measured by proportion of patients retained in each treatment

Urine toxicology

Predictors of treatment compliance

Adverse events

Proctor, 2014

USA

Retrospective chart review

Duration: 24 weeks

N = 3233

Mean age:

Male: 55.9% Methadone,

57.8% Buprenorphine (Suboxone), 50.05% Buprenorphine (Subutex)

(1) Methadone 64.64 mg/d

(2) Buprenorphine (Suboxone) 9.75 mg/d

(3) Buprenorphine (Subutex) 12.21 mg/d

Retention in treatment as measured by length of stay in days, and percent of patients retained in each treatment

UDS Findings

Moderate Risk

Schottenfeld, 1997

USA

Randomized controlled trial Double blind

Duration: 24 weeks

N = 116

Mean age:

32.6 years old Methadone-65,

32.6 years old Buprenorphine-12,

31.6 Methadone-20,

33.7 Buprenorphine-4

Male:

57% Methadone-65,

69% Buprenorphine-12,

72% Methadone-20,

77% Buprenorphine-4

(1) Methadone 20 mg

(2) Methadone 65 mg

(3) Buprenorphine 4 mg

(4) Buprenorphine 12 mg

Treatment retention as measured by completion rates

Urine toxicology