Drug substitution programmes

This summary is based on two systematic reviews: Egli et al. (2009) reviewed 46 studies and compared the relative merits of prescribing methadone and other substances as a substitute for heroin. Perry, et al. (2013) reviewed 11 studies. Both reviews were concerned with the overall effect of drug substitution programmes on rates of offending. The reviews considered a range of different drug substitutes compared to non-pharmacological interventions such as counselling, probation or no treatment and also comparisons of different drug substitutes. Overall, the evidence suggests that drug substitution programmes can reduce crime, but the evidence is mixed and dependent on the drug substituted or the treatment used.

Studies reviewed

Average impact

Certainty of impact


System readiness


Positive effect


Not evaluated


What is it?

Problematic drug use and drug addiction can have a number of criminogenic effects. Drug users can be drawn into crime through simply buying illegal drugs, and they can also engage in acquisitive crime in order to fund a drug habit. There are also health and quality of life issues associated with drug addiction.


Drug substitution programmes are based on a harm reduction approach to drug dependency, rather than a criminal justice approach. The idea is that reducing the risks or illegality associated with drug taking reduces a range of harms. This has more beneficial long-term consequences for drug users than simply exposing them to criminal justice sanctions. It also benefits society by reducing criminal activities and public disorder caused by drug users.

Should it work?

Programmes aim to help drug-dependent offenders gain greater control over the type of drug they take, the amount they take, and the frequency with which they take it. There are two broad approaches. The first approach is to substitute illegal drugs with legal alternatives, such as methadone for heroin users. The second is to formally prescribe illegal drugs so that users do not have to acquire them through illegal means. Either approach should result in a reduction in the amount of drugs that are consumed and related harms. There should also be a reduction in offending related to problematic drug consumption including shoplifting, theft, and public order offences.

Does it work?

Overall, the evidence from both reviews suggest that drug substitution programmes can reduce crime. However, the evidence is not emphatic, and the effects vary depending on the different forms of treatment.

Egli et al. (2009) found that heroin maintenance reduces crime significantly more than methadone maintenance. Methadone maintenance was not associated with significant effects on criminal behavior. The review does note some large and significant effects of methadone with respect to pre-treatment levels, but it does not define these effects. The effects of other substitute drugs were mixed. Naltrexone was found to reduce criminality significantly more than either behavioural therapy or counselling, whilst buprenorphine was not found to significantly reduce criminal behavior.


Perry, et al. (2013) found that methadone and buprenorphine substitution were not effective in reducing offending compared to non-pharmacological treatments, but that naltrexone did significantly reduce offending. The review concluded that pharmacological interventions for drug-using offenders did appear to reduce subsequent drug use and to a lesser extent offending. There were differences between the three pharmacological interventions (buprenorphine, methadone and naltrexone) when compared to a non-pharmacological intervention, but not when compared to each other. The authors state that caution should be taken when interpreting the findings of their review, because of the small number of trials and the high risk of bias in some of the trials.

How strong is the evidence?

The review by Egli et al. (2009) consisted of a systematic review (43 studies) and a meta-analysis (21 studies). To be eligible, studies had to assess the effects of any substitution therapy (using e.g. methadone and/or opiates as substitution drugs). Only the effects on offending were considered. Meta-analytic techniques were used to identify overall effects of several substances. Comparisons of different treatments (i.e. substitution vs. any other treatment) were restricted to studies meeting levels 4 or 5 on the Maryland Scale (Sherman et al. 1997). Randomized studies, quasi-experimental studies and before-after comparisons on the effects on offending of drug substitution programs were included. The report is not always clear on which of the studies are being reported on, and does not clearly differentiate between the systematic review and meta-analysis when reporting the findings.


Perry, et al. (2013) subjected 11 randomised controlled trials to meta-analysis. The trials all assessed the efficacy of any pharmacological interventions for reducing, eliminating or preventing relapse in drug-using offenders. The review used standard methodological procedures as described by The Cochrane Collaboration. 17 trials met the inclusion criteria for the review, but six of these were awaiting classification when the review was conducted. The remaining 11 trials contained 2,678 participants. Nine of the eleven studies used samples with a majority of men. The interventions were compared to non-pharmacological treatments and other pharmacological drugs. The review found that overall the methods were poorly described and most studies were rated as ’unclear’. There were various risks to bias.

Is it worth it?

Neither of the reviews described a cost-benefit analysis, although Perry et al. (2013) provide a descriptive analysis of costs in a separate report.

Can it be implemented?

Egli et al. (2009) state that dosage is important for to the short and long terms success of some of the substitution programmes studied, but that there was a need for more research into this.

What’s missing from the evidence?

Whilst crime reduction is an important aim of drug substitution, other potential benefits of such programs should be researched, including health impacts and the effects on long term abstinence. As noted above, the implementation and respective cost benefits of the different programmes are under-researched at present. There is also a focus on male offenders, so more research into the use of substitution programmes for female offenders is needed.


Egli, N., Pina, M., Skovbo Christensen, P., Aebi M. F. and Killias, M. (2009) ‘Effects of drug substitution programs on offending among drug-addicts’, Campbell Systematic Reviews, 2009:3Perry, A. E., Neilson, M., Martyn-St James, M., Glanville, J. M., McCool, R., Duffy, S, Godfrey, C. and Hewitt, C. (2013) ‘Pharmacological interventions for drug-using offenders’, Cochrane Database of Systematic Reviews 2013, Issue 12.