Between October 2008 and March 2009, injecting drug users attending harm reduction centers in Catalonia (Spain) were interviewed. Inclusion criteria were having used opioids (heroin, methadone or other opioids) and injecting any drug in the 6 months prior to the interview, and having signed an informed consent form. This informed consent form clearly stated the confidentiality of the study. The 18 Harm reduction centers included needle exchange programs, outreach programs, and three supervised injecting facilities. Most harm reduction centers included in the study (11 out of 18) were located in Barcelona or in its metropolitan area. A convenience stratified sample of injecting opioid users was selected (n=729).19 Assignment to strata was proportional to the volume of visits in each center and to the percentage of individuals in each center by country of birth. In centers with less than 5% foreign-born clients, only native participants were recruited. Participants were randomly selected within harm reduction centers.

Face to face interviews were conducted in each center by trained interviewers using an anonymous structured questionnaire, adapted from the Itinere3 and World Health Organization20 questionnaires. Information was collected on socio-demographic variables, patterns of drug use, use of social and health services, and non-fatal opioid overdoses. The questionnaire was provided in 4 languages (Spanish, Romanian, English, and French), and piloted with a group of 15 IDUs from several countries before its administration. Interviewers were weekly monitored to control the quality of data collection.

Overdose was defined as an episode occurring due to heroin, methadone or other opioids use, in which after drug use, extreme difficulty in breathing, loss of consciousness and problems waking up or recovering consciousness, and sometimes bluish skin or lips would appear.21 Participants were asked, in two open ended questions, to list the three main reasons for an overdose to occur, as well as the three main actions to undertake in case of witnessing an overdose. Respondents received 24€ to encourage participation. The study protocol of the REDAN study was approved by an Ethics Committee Review Board (Hospital Universitari Germans Trias i Pujol, Badalona, Spain).

The study included 729 participants, of which 379 were recruited within the city of Barcelona. The sample was 82.6% male, median 36 years of age (20-59 years). Most participants had completed secondary education (Table 2). There were no statistically significant differences in most characteristics by sex, with the exceptions of having received most of their income in the previous 6 months from irregular or marginal activities and being immigrant. The vast majority of participants had injected drugs during the previous month, but only half of them injected drugs on a daily basis. In the previous 6 months, almost all participants were using at least 3 different drugs (95.3%) and had used syringe exchange programs (95.6%; data not shown). Most participants had at some point in their lives received drug dependency treatment (86.4%), and half underwent treatment at the time of the interview (49.7%), but only 27% had ever attended overdose prevention courses.

Overall, 28.7% of participants had limited knowledge about overdose prevention, since they could not cite more than two risk factors and/or adequate actions to undertake if witnessing an overdose. When separated by origin, 25.7% of native respondents presented limited knowledge, versus 40.4% of participants from Eastern Europe and 22.6% among participants from other countries (Figure 1). Differences in prevalence of limited knowledge were significant when comparing native and Eastern Europeans (p<0.001) as well as when comparing Eastern Europeans with immigrants from other countries (p<0.01).

Figure 1.

Distribution of opioid injectors recruited in Catalonian harm reduction centres (2008-2009) by number of adequate risk factors and/or actions related to opioid overdose cited, and by country of birth (%).

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Crude prevalence of limited knowledge about overdose prevention was significantly higher in people who came from Eastern European countries, were not receiving or had never received drug dependency treatment, never had suffered an overdose, never had attended overdose prevention courses, injected drugs on a daily basis, or had better or similar self-perceived health than their age peers (Table 3). Use of supervised injecting facilities was not significantly associated with knowledge about overdose prevention.

After adjusting for other factors, those participants with primary or lower educational level (PR=1.50, 95% CI:1.16-1.94), coming from Eastern European countries (PR=1.71, 95%CI: 1.29-2.26), never having undergone drug dependency treatment (PR=1.52, 95% CI:1.17-1.99) and never having suffered an overdose (PR=1.37, 95% CI:1.07-1.75) had higher probability of presenting limited knowledge about overdose prevention (Table 3).

In this sample, 30.6% of injecting opioid users did not identify any risk factor for overdose, 51.3% identified one and 18.1% identified more than one. Native participants cited more frequently inadequate reasons for overdose, and especially the use of adulterated or cut heroin (Figure 2a). Notably, 5.2% cited the use of the injected route of administration as a risk factor for an opioid overdose.

Figure 2.

Percentages of participants mentioning each reason and action related to opioid overdose by country of birth among opioid injectors recruited in Catalonian harm reduction centres, 2008-2009.

A) Reasons to suffer an opioid overdose

B) Actions to undertake in case of witnessing an opioid overdose.

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In addition, 35.9% IDUs in the sample did not identify any adequate action in case of witnessing an overdose, 61.1% identified one, and only 3% identified two. Calling an emergency service (61.9%) and giving first aid (56.5%) were the most frequently cited adequate actions in case of witnessing an overdose. Naloxone administration was the sixth most frequent cited adequate action, and native participants seemed less familiar with this action (3.8%) than their foreign peers (10.1% Eastern Europeans, 11.1% other countries). In contrast, Eastern European participants cited very frequently the injected administration of substances different from naloxone (typically saline or water with lemon), whereas native participants very rarely mentioned this inadequate practice (Figure 2b).

This study poses the strength of exploring in detail a relevant topic which has been poorly studied, namely knowledge about opioid overdose prevention in an IDU population. Although we cannot assure that the sample is representative of opioid injectors as a whole in Catalonia, this study reaches a large sample out of a hidden population, generally very difficult to access and which bears enormous social barriers. The sample is representative of those injecting opioid users who attended Catalonian harm reduction centers, since assignment to strata was proportional to the volume of visits in each center and to the percentage of individuals in each center by country of birth, and since sample selection was random within the centers.

The dependent variable, limited knowledge about overdose prevention, is not straightforward, but it is informative about those participants presenting reduced knowledge about overdose prevention. This variable includes information about risk factors and adequate peer assistance. There is an underreporting of well-known risk factors for overdose among this sample, such as using the injected route of administration. It is possible that participants do not identify such risk factors spontaneously, but would recognize them if they would appear as a list of pre-coded questions, as was indeed the case in another study.21 It is also possible that participants have taken for granted those risk factors.

A large proportion of participants cited consuming adulterated or cut heroin as a risk factor for overdose, even though this is considered an erroneous belief by the scientific community, as cited elsewhere.21 It is possible that this myth is encouraged by the fact that prevention messages associated with concerns about purity or amount coincide with those regarding adulterated heroin. Using a large amount of drug as a risk factor for suffering an opioid overdose was the most frequently cited reason, as in other studies.12,21

Other authors21 reported a prevalence of 57.2% regarding limited knowledge of overdose risk factors (less than two risk factors), against our 81.9% prevalence for the same variable. This difference could lie in the fact that our study population is older and less educated than that making up the Itinere cohort.3,21

To be effective and to have a positive impact in knowledge, overdose prevention programs must achieve high coverage, reaching most of the IDUs population.24 In Spain, harm reduction programs were implemented during the 1990s, especially methadone maintenance treatment and syringe exchange programs. These were set up later than in other EU countries, and introduction was heterogeneous throughout the country.25–28 Although overdose prevention interventions had been working in Barcelona for over 8 years at the time of the interviews,25–27 these interventions have only recently been implemented in a systematic way.

In this study, only 27% of the participants reported ever having attended overdose prevention courses. Even though they presented lower prevalence of limited knowledge than their peers, this difference was not statistically significant, and neither was the association measure (adjusted prevalence ratio). Other studies21,29,30 have reported better scores regarding overdose prevention knowledge in those IDUs attending courses or IDU-oriented resources. We would expect finding an association between knowledge about overdose prevention and access to health care services, but in our sample, use of harm reduction resources (supervised injecting facilities and overdose prevention courses) does not seem to protect against limited knowledge. However, Harm Reduction strategies have played an important role in other aspects of community health. Hence, injected drug use has overall decreased in Spain while syringe exchange programs have been expanded.25

Interestingly, participants who had never been exposed to treatment for their drug use did present significantly higher prevalence of limited knowledge about overdose prevention. Other studies had reported that exposure to opioid maintenance treatment reduced long-term risk of overdose death.31,32 In our study, participants who had undergone previous treatment were less prone to presenting limited knowledge. If knowledge levels translate into adequate preventive behaviors, it is possible that, until the study period, treatment centers were more efficient at delivering correct information, and therefore at preventing overdose episodes, than were overdose prevention courses. Further studies are needed to evaluate the performance of more recently implemented, systematic overdose prevention programs. Additionally, efforts should continue to make the most of those opportunities presented in each treatment episode, further spreading preventive messages in the community.

Other individual factors associated with limited knowledge about overdose prevention in this study were the country of origin (Eastern European countries), having a low educational level, and never having experienced an overdose before. IDUs who have already suffered non-fatal overdose episodes are more likely to be experienced drug users, with a history of exposure to different IDU-oriented resources including treatment and harm reduction, and probably having received a broad array of preventive messages.

Country of origin and low educational level likely have contributed a negative effect on understanding complex messages, such as those supplied in overdose prevention courses, since initially the content of such courses was neither provided in other languages nor tailored to low literacy populations. In this sense, special efforts should be made to provide specific responses to IDUs with limited Spanish/Catalan knowledge and low literacy. In the Catalonian case, where there are higher proportions both of IDUs and of immigrant drug users than in other Spanish regions, ad hoc programs should be developed accounting for users’ specificities, such as idiomatic barriers and/or functional illiteracy stemming from a low educational level. Moreover, as the proportion of foreign-born users in IDU-oriented resources increases, and since immigrants in Spain tend to make less use of health services than natives,33,34 specifically targeted interventions should be developed to assure an increased access to such resources.

In conclusion, our findings suggest that harm reduction and overdose prevention programs, though implemented for almost a decade,25–28 and though successful in many other aspects, might not have had a significant impact in reducing limited knowledge about overdose prevention among injecting opioid users in Catalonia at the time of the interviews. It is of vital importance to continue developing extensive, methodologically systematic overdose prevention programs, especially designed to address idiomatic, educational and cultural differences, in order to improve knowledge about overdose prevention and to reduce potentially harmful beliefs persisting in the community. All IDU-oriented resources should be included in such programs, particularly treatment centers and harm reduction resources, in order to maximize their effect. Qualitative research should be undertaken to better understand the barriers to acquiring knowledge and how this translates into actions at overdose events among the injecting population. This research should then inform the development of future overdose training programs and their evaluation.