Table 1

Characteristics of included studies

Study/
Country
DesignParticipantsInterventionsOutcomesRisk ratingEmbedded Image
Clark et al28
Australia
Crossover 
Randomised controlled trial (RCT)
Open-label;  Duration: 12 weeks
n=11
Mean age: 36.5 years
Use of heroin: once per week
Heroin use disorder and were on methadone
(1) Morphine
Flexible starting dose increased by 50 mg per day following transfer, never exceeded 800 mg/day
(2) Methadone
Flexible starting dose reduced by 12 mg per day following transfer
Retention
Severity of opiate withdrawal symptoms
Heroin or other substance use
Severity of dependence
Mental health/social functioning
Embedded Image
Eder et al26
Austria
Crossover
Randomised double blind,
double-dummy;  Duration: 14 weeks
n=64
Mean age: 28 years
Male: 75%
Opioid use disorder (OUD) (excluded patients already receiving maintenance therapy)
(1) Morphine
Starting dose 200 mg/day increased to 800 mg/day by week 1
(2) Methadone
Starting dose 40 mg/day increased to 100 mg/day by week 1
Retention
Use of illicit substances based on urinalysis
Extent of drug cravings
Withdrawal symptoms
General well-being
Safety was assessed on the basis of adverse events and clinical and physical examination
Quality of life (QoL) measured by the Lancashire Quality of Life Profile
Embedded Image
Giacomuzzi 
et al27
Austria
RCT
Open-label; 
Duration: 24 weeks
n=120
Mean age: 27 years;
Male: 57%
OUD and were on methadone
(1) Morphine;
maintenance dose dependent on severity of withdrawal symptoms
(2) Methadone;
maintenance dose dependent on severity of withdrawal symptoms
(3) Buprenorphine; maintenance dose dependent on severity of withdrawal symptoms
Retention (from personal correspondence)
QoL measured by the Lancashire Quality of Life Profile
Withdrawal symptoms measured by the Opioid Withdrawal Scale
Embedded Image
Beck et al17
Switzerland and Germany
Crossover RCT
Open-label
Duration: 22 weeks
n=276
Mean age: 38.1
Male: 81.5%
Opioid dependence and were on methadone
(1) Methadone; Flexible dosing
Crossover at 11 weeks to morphine
(2) Morphine; Flexible dosing
Crossover at 11 weeks to methadone
Retention (24 weeks)
Proportion of positive urine samples per patient (12 weeks)
Per treatment for co-consumption of heroin
Craving heroin
Craving cocaine
Self-reported drug use
Mental health problems (SCL-27)
Positive urine samples
Adverse events
Embedded Image
  • Risk rating legend:

  • A—random sequence generation (selection bias); amber circle: unclear; B—allocation concealment (selection bias); C—blinding of participants and personnel (performance bias); D—blinding of outcome assessment (detection bias); E—incomplete outcome data (attrition bias).