INTRODUCTION

Opioid use has evolved over the years, changing from their origins in the Second World War, to the 80s and 90s when they became a worldwide problem¹. The use of injected heroin was associated with severe marginalisation, increased crime and a higher risk of infection from diseases such as the human immunodeficiency virus (HIV). Spain saw an exponential growth of HIV+ cases amongst drug addicts in this period, which led to the approval of a range of legislative measures on interventions with methadone for patients with opioid dependency².

The healthcare scenario also brought about a change in the organisational model in Spanish prisons, which led to the introduction of the methadone maintenance program for inmates. A Royal Decree was published in 1990 that regulated the use of and access to this intervention, which was not enacted for several years. Since then, new treatment programs have been introduced that are geared towards abstinence from substances, such as drug-free programs, and multidisciplinary interventions have also been established³.

These programs are one of the treatments of choice for heroin dependence. They include personalised oral administration of an opioid agonist (methadone). They form part of a set of harm reduction activities and strategies, which consist of individual and collective social and medical measures that set out to eliminate the negative effects of drug use in the dependent population^4,5.

According to the results of the 2022 Spanish Survey on Health and Drug Use amongst Prison Inmates (ESDIP), the percentage of opioid users in Spanish prisons has gone down in recent years, although there are still many amongst the prison population. According to the 2017 memorandum on drug abuse published by the Ministry of Health and Consumer Affairs, the prevalence of the methadone maintenance program, which was introduced in 1994, dropped over the years and was replaced by other drug rehabilitation approaches in response to the changes in consumption patterns amongst the prison population. The general objective of this study is to evaluate the effectiveness of opioid maintenance programs when treating drug dependence in Spanish prisons⁶.

MATERIAL AND METHOD

For this review, a bibliographical search of the following databases was carried out: PubMed, Cochrane, IBECS, LILACS, HealthCare, all of which were available at the library of the Universitat Jaume I de Castellón. The resources available at other entities such as the Spanish Ministry of Health and Consumer Affairs and the Spanish Journal of Prison Health (Revista Española de Sanidad Penitenciaria (RESP)) were also used.

Descriptors included in health sciences in Spanish were used, along with others in English included in medical subject headings, as indicated in Table 1.

The terms used for the bibliographical search were mainly: methadone, prisons, and buprenorphine in combination with the connectors AND and OR as follows: methadone AND prisons; opiate substitution treatment AND prisons; methadone AND buprenorphine; methadone OR buprenorphine; prisons AND methadone AND buprenorphine.

The language limits established were publications in Spanish, English and Catalan and the period of publication was limited to between January 2011 and November 2021.

The inclusion criteria applied were: freely accessible articles, based on recent studies. The exclusion criteria on the other hand were: articles duplicated in different databases, articles with no relevant information related to opioid rehabilitation programs and articles that were published more than ten years ago.

Figure 1. Flow chart of study. 

The results are reflected in Figure 1 after the application of the aforementioned strategies for the obtaining the items.

RESULTS

A total of 647 articles were obtained at the end of the bibliographical search. Filters belonging to each data base were then used and 616 articles were eliminated. Duplicates found in the searches were also rejected (n = 11), and finally a reading session of the title and abstract of the articles of interest for the subject matter in question was carried out, after which 20 articles were selected.

Of the 20 selected articles, 70% (n = 14) were reviews of the literature, 5% were cohort studies (n = 1), another 5% were cross-sectional studies (n = 1), 10% were studies of cases and controls (n = 2), 5% were quasi-experimental studies and 5% were field research articles.

Table 2 contains a summary of the characteristics of each article selected for this review: the type of study, the date and country of publication, and the aims and conclusions reached.

DISCUSSION

The predominance of methadone based interventions is highlighted in a study by Martínez⁷, who indicates that the most widely used programme for opioid rehabilitation in Spanish prisons is the methadone maintenance program (MMP), which was used by a large sector of the prison population in the years immediately following its introduction, while the number of participants in this type of program has since gone down. In similar studies, Martín et al.⁸⁾ and Torrens et al.⁹ also comment on the large number of inmates who receive this treatment. However, Narezo et al.¹⁰, while agreeing with the number of individuals who participate in the program, states that other methods of detoxification are growing in terms of the number of users, while there is a gradual decrease in the popularity of MMPs .

Several studies highlight the different adverse effects of treatment with methadone. One of the most frequently mentioned of these is the prolongation of the QT interval . Bart et al.¹¹ state that this effect can lead to a type of cardiac arrhythmia called torsade de pointes, although the repercussions for the heart are not clinically significant, given that the rate of associated cardiovascular events is very low. Barbosa et al.¹² also mention this effect, but add that there is insufficient evidence to back up this effect on patients with no previous history of cardiovascular risk, although at the same time they recommend a preventive electrocardiogram for users.

Salsitz et al.¹³ likewise concur with this side effect, and include other adverse effects, such as a certain degree of sedation, excessive sweating, increased appetite and a reduction in testosterone levels caused by the inhibitory action on the gonadotropin-releasing hormone of methadone, which may lead to sexual dysfunctions.

Soyka et al.¹⁴ adds other symptoms and signs to the ones mentioned by Salsitz et al.¹³, respiratory depression, sensations of euphoria and possible tolerance and physical dependence. When considering the last of these adverse effects, Barbosa et al.¹²⁾ comments that methadone, within the parameters of potential tolerance or dependence that any opioid can cause after someone has been taking a different one, is a less sensitive substance in this regard and so the risk of this condition arising is minimal.

Green et al.¹⁵ state that there is a link between methadone consumption and poor dental conditions, as there is a high prevalence of caries, poor dental hygiene, dry mouth and bruxism amongst subjects receiving treatment.

Another possible adverse effect mentioned by authors is the impact on cognitive functions. Mindt et al.¹⁶ comment that methadone maintenance treatment has a low effect on such functions, but it can interfere with executive functioning (abstract thinking, the ability to make plans, initiate actions and complex behaviours, etc.), memory, learning, visuospatial functions, language, speed of processing stimuli and attention span.

Several authors, such as Gowing et al.¹⁷, Clark et al.¹⁸ and Marco et al.¹⁹, agree that this program has been very effective in reducing illegal opioid consumption and HIV transmission, since it has brought about a change in high risk behaviours of consumption and has reduced the incidence of IDU and syringe exchanges.

Schwartz et al.²⁰ likewise state that such interventions have reduced criminality and the number of arrests related to opioid use, affirmation which they agree in another article by Schwartz et al.²¹, as well as Flórez et al.²². On the other hand, Perry et al.²³ did not find enough evidence to conclude that there is a link to reduced criminal behaviour. They consider that it would be a variable that depends on the type of offence, the likelihood of rehabilitation and the setting of the person receiving treatment, rather than just being in a program.

One new alternative treatment option for rehabilitation was recently placed on the market: extended-release buprenorphine/naloxone. Soyka et al.¹⁴⁾ comment that the program consists of a depot release drug of buprenorphine/naloxone, based on weekly injections of a range of doses that can be extended to monthly ones. This implies better pharmacological management and control and greater ease of administration, unlike methadone. Chappuy et al.²⁴ support this assertion.

Marco et al.¹⁹ and Fuentes et al.²⁵ compared the effectiveness of MMPs with other rehabilitation treatments used in the prison setting, and indicate that both methods have obtained similarly favourable results, although they mention some important differences. Both studies showed that inmates treated with buprenorphine are usually more likely to continue with the treatment once they are released. On the other hand, Vera-Remartínez²⁷, states that treatment with buprenorphine/naloxone is safer, thanks to the naloxone in the composition, which is an antagonist for overdoses of opioids and maintains the levels of buprenorphine within therapeutic ranges. For the same reason Soyka et al.¹⁴ affirm that, unlike methadone, buprenorphine/naloxone entails a lower risk of overdose and respiratory depression, making the use of this combination safer than methadone.

Salsitz et al.¹³ add that buprenorphine/naloxone has a lower incidence of adverse effects related to prolonged QT intervals and reduced libido.

Along the same lines, Vorspan et al.²⁶ add another advantage of buprenorphine/naloxone over methadone in dosage adjustment. According to the authors, methadone requires a period of progressive increases of the dosage until the right one is reached in the first weeks of treatment, while buprenorphine/naloxone has just three different doses, making it easier to adapt to the individual. The final significant differences according to Maas et al.²⁸ is the difference in price between the two products; methadone is cheaper than buprenorphine, which implies a better cost/effectiveness ratio for methadone.

Some limitations to this study have been identified, such as the lack of recent and useful information about methadone maintenance programs in the Spanish prison setting, and so we recommend more rigorous research to obtain more up to date information and to carry out a better cost/effectiveness balance between the different interventions. Training of professionals in management and safety of this type of therapy is also recommended.

CONCLUSION

After reviewing the bibliography, the conclusion is that MMPs are a widely used interventional approach in Spanish prisons, and that they have been shown to improve inmates' quality of life by reducing the illegal use of opioids and improving their behaviour. However, adverse effects associated with the use of methadone were also observed.

Buprenorphine/naloxone appears to be a better option when compared to methadone because it is safer in cases of overdosing and also reduces some adverse effects. The new extended-release pharmaceutical forms also offer greater patient comfort, avoid misuse of the product and facilitate adherence and reintegration into society once inmates are released.