Continuing injecting risk behaviour: results from the Amsterdam Cohort Study of drug users

Similarities and changes between 15- and 24-year survival and retention rates of patients in a large medical-affiliated methadone maintenance treatment (MMT) center

BACKGROUND

Environmental and social trends and patients' characteristics may affect predictors for methadone maintenance treatment (MMT) outcome.

METHODS

We have expanded our previous study of predictors for MMT outcome (from 619 to 890 patients) and the study period (from 15 to 24 years). Survival and retention in MMT since admission to the MMT clinic (6/1993-6/2016) and until death or study closure (6/2017) were compiled and analyzed.

RESULTS

Of 890 patients ever admitted (10,146.9 person-years (py)), 237 passed away (116 while in MMT). The mortality rate did not differ between those who stayed or left (2.6 vs. 2.1 per 100 py, p = 0.1), but it was lower among those who stayed ≥1 year during any admission (2.1 vs. 3.3 per 100 py, respectively, p = 0.004). Age <40 years, no hepatitis C or B, no HIV, and no benzodiazepine abuse after one year predicted longer survival (multivariate analyses). No opiate or benzodiazepine abuse after one year, methadone dose ≥100 mg/d, no DSM-IV-TR Axis II diagnosis only, and no direct hospital referral predicted longer retention. Cocaine abuse predicted poor retention and survival among 271 patients admitted during the extended part of the study period.

CONCLUSIONS

Predictors for retention (associated with MMT outcome) and mortality (associated with pre-treatment comorbidity) after 24 years were similar to those after 15 years. Cocaine abuse as a predictor of both poor retention and poor survival in the later period may reflect the escalating trend for cocaine abuse and should be studied if related to other unmonitored substances.

The influence of the perceived consequences of refusing to share injection equipment among injection drug users: balancing competing risks

Injection drug users (IDUs) are at risk for HIV and other bloodborne pathogens through receptive syringe sharing (RSS) and receptive paraphernalia sharing (RPS). Research into the influence of the perceived risk of HIV infection on injection risk behavior has yielded mixed findings. One explanation may be that consequences other than HIV infection are considered when IDUs are faced with decisions about whether or not to share equipment. We investigated the perceived consequences of refusing to share injection equipment among 187 IDUs recruited from a large syringe exchange program in Los Angeles, California, assessed their influence on RSS and RPS, and evaluated gender differences. Two sub-scales of perceived consequences were identified: structural/external consequences and social/internal consequences. In multiple linear regression, the perceived social/internal consequences of refusing to share were associated with both RSS and RPS, after controlling for other psychosocial constructs and demographic variables. Few statistically significant gender differences emerged. Assessing the consequences of refusing to share injection equipment may help explain persistent injection risk behavior, and may provide promising targets for comprehensive intervention efforts designed to address both individual and structural risk factors.

Trajectories of injection drug use over 20 years (1988-2008) in Baltimore, Maryland

The objective of this study was to identify longitudinal patterns of injection drug use over 20 years in the AIDS Linked to the Intravenous Experience (ALIVE) Study, a community-based cohort of injection drug users (IDUs) in Baltimore, Maryland, with a focus on injection cessation. Starting in 1988, persons over 18 years of age with a history of injection drug use were recruited into the study. Participants provided information on their injection drug use semiannually through 2008. The analysis was restricted to 1,716 IDUs with at least 8 study visits. Finite mixture models were used to identify trajectories and predictors of injection patterns over time. The mean age of participants was 35 years; 75% were male, and 95% were African-American. Five distinct patterns were identified: 2 usage patterns (32% engaged in persistent injection and 16% had frequent relapse) and 3 cessation patterns (early cessation (19%), delayed cessation (16%), and late cessation (18%)). A history of drug treatment, no recent use of multiple substances, and less frequent injection distinguished the early cessation group from the other groups. This study demonstrated multiple trajectories of drug injection behaviors, with a substantial proportion of IDUs stopping injection over extended time frames. For maximum effectiveness, public health programs for IDUs should be long-term, comprehensive, and targeted toward individual patterns of use.

The perceived consequences of safer injection: an exploration of qualitative findings and gender differences

Injection drug users (IDUs) are at a risk for HIV and other bloodborne pathogens via syringe and paraphernalia sharing, with females being at elevated risk. Consequences of injection risk behavior such as the risk of becoming infected with HIV have been relatively well studied, though less is known about the consequences of refusing to share injection equipment. We conducted indepth qualitative interviews with 26 IDUs recruited from a syringe exchange program in Los Angeles, California, USA, to understand the consequences of refusing to share injection equipment and to determine whether these perceived consequences differ by gender. Perceived consequences were organized into four domains using a social ecological framework: microsystem (perceived risk for HIV, drug withdrawal or forgoing drug use), exosystem (trust and social norms), mesosystem (precarious housing and shelter policies), and macrosystem (syringe access/inconvenience, economic and legal consequences). Gender differences were identified in some, but not in all areas. Effective public health interventions among IDUs will benefit from a holistic perspective that considers the environmental and social rationality (Kowalewski, M., Henson, K.D., & Longshore, D. (1997). Rethinking perceived risk and health behavior: A critical review of HIV prevention research. Health Education and Behavior, 24(3), 313-325) of decisions regarding injection risk behavior and assists individuals in addressing the consequences that they perceive to be the most salient.

Needle exchange and sexual risk behaviors among a cohort of injection drug users in Chicago, Illinois

OBJECTIVE

To examine the impact of a needle exchange program (NEP) on sexual risk behaviors of injecting drug users (IDUs).

METHODS

: Between 1997 and 2000, 889 IDUs in Chicago were recruited from NEPs and an area with no NEP into a cohort study. They were interviewed and tested for HIV at baseline and 3 annual follow-up visits. Random-effect logistic models were used to compare NEP users and nonusers regarding the number of sex partners, number of unprotected sex acts, and frequency of condom use.

RESULTS

Compared to NEP nonusers, NEP users had a similar number of sex partners over time, but had 49% higher odds of using condoms with their main partners (P = 0.047). At baseline, there was no difference between NEP users and nonusers in episodes of vaginal intercourse, but over time the odds of having a higher number of unprotected instances of vaginal intercourse were reduced by 26% per year for NEP users but only 10% per year for nonusers (P = 0.02).

CONCLUSION

This study suggests that NEP participation may help reduce the absolute risk of HIV sexual transmission.

FibroScan used in street-based outreach for drug users is useful for hepatitis C virus screening and management: a prospective study

Although hepatitis C virus (HCV) infection prevalence is high among drug users, they do not commonly receive regular care in academic centres. The aim of this prospective study was to assess the influence of FibroScan use on HCV screening and management in street-based outreach. From January 2006 to January 2007, all consecutive drug users were offered noninvasive evaluation of liver fibrosis with FibroScan. After FibroScan, parameters were recorded with a structured, face-to-face questionnaire by outreach workers. All 298 subjects accepted FibroScan evaluation drug use was--ever injected heroin (69%), ever snorted or injected cocaine (89%), current chronic alcohol abuse (44%). The median FibroScan score was 5.3 kPa. Before blood sampling, 34% of subjects reported HCV positivity. HCV positivity was found in 83 cases. All these subjects had positive HCV-RNA. Forty-five subjects agreed to meet a hepatologist. By multivariate analysis, never snorted cocaine, consumed alcohol < 21 drinks per week, duration of injected heroin > 7 years, and FibroScan > 7.1 kPa were significantly associated with HCV positivity. Thus in a street-based outreach service for drug users, the acceptance of FibroScan is excellent. FibroScan with a hospital-based physician may facilitate screening and management of drug users for HCV infection.

Impaired cytokine production and suppressed lymphocyte proliferation activity in HCV-infected cocaine and heroin ("speedball") users

HCV-infected "speedball" users (n = 30) were selected from an original cohort of 400 intravenous drug users for cytokine analysis. Cytokine concentrations (TNF-alpha, IL-1beta, IL-6, IFN-gamma, IL-2, IL-4, IL-10 and IL-12) were determined in plasma and peripheral blood mononuclear cells (PBMC) cultures derived ex vivo from these patients. In addition, lymphocyte proliferation was measured in 49 HCV-positive "speedball" users. TNF-alpha, IL-6, IFN-gamma, IL-2, IL-4, IL-10, IL-12 cytokines and not IL-1beta were significantly increased in plasma from HCV-positive "speedball" users compared with healthy controls. Except for IL-10, all other cytokines measured were augmented in phytohemagglutinin-stimulated PBMC cultures from HCV-positive "speedball" users. Likewise, overproduction of cytokines TNF-alpha, IL-1beta, IL-6 and IFN-gamma, was consistently detected when PBMC cultures from HCV-positive "speedball" users were stimulated with a biological response modifier. However, HCV-infected "speedball" users showed significant reduction in lymphoproliferative activity. Compared with healthy subjects, there was a consistent overproduction of both TH1 and TH2 type cytokines in the plasma and PBMC's of HCV-infected "speedball" users. Furthermore, there was a persistent reduction of lymphoproliferative activity in this group. These immunologic abnormalities, coupled with the range of response between the two TH-types in HCV-infected "speedball" users, suggest impairment in the regulatory mechanism of the TH1-TH2 system.

Strong HIV and hepatitis disclosure norms and frequent risk behaviors among Hungarian drug injectors

Ethnographic interviews and focus groups were conducted between May 2003 and January 2004 among injection drug users (IDUs; n=29) in Budapest, Hungary, to assess knowledge related to HIV, hepatitis B (HBV), and hepatitis C (HCV) and norms, attitudes, and behaviors. Participants perceived themselves at low risk for infection with HIV but at high risk for hepatitis through injection but not sexual exposure. They reported strong disclosure norms for HIV and hepatitis infections, while sexual and injection risk behaviors were influenced by trust about partners' self-report of infection status. Injection networks were small, with infrequent syringe sharing among a few close friends. Cookers and drug filters often were shared, and filters were reused as a backup drug supply. Most sexual relationships were monogamous, and condoms were used rarely. Although participant norms supported HIV/HBV/HCV testing, the lack of available behaviors with injection and sex partners who are close friends. Network interventions among IDUs in Hungary should build on disclosure norms and trust to reduce injection and sex risk. Testing services should be expanded and access increased so that IDUs can act on and reinforce their norms for testing.

Discrete-trials heroin self-administration produces sensitization to the reinforcing effects of cocaine in rats

RATIONALE

The prevalence of cocaine use in opioid-dependent individuals is reportedly high, and the associated negative health and social consequences are severe and well documented. Sensitization of the reinforcing effects of cocaine has been demonstrated following noncontingent opioid exposure in animals; however, no preclinical studies have investigated the impact of opioid self-administration on cocaine's reinforcing effects.

OBJECTIVE

Experiments were designed to investigate whether access to heroin self-administration altered the subsequent reinforcing effects of cocaine.

METHODS

Baseline responding for cocaine under a progressive ratio schedule was first established. Heroin was then self-administered under a 24-h discrete-trials procedure (DT5; access to heroin five times per hour). Subsequently, cocaine-maintained responding was reassessed.

RESULTS

Here we demonstrate that 10 days of DT5 heroin self-administration (50 microg/kg per infusion) resulted in an increase in cocaine's reinforcing effects at several doses across the cocaine dose-effect curve (0.38-3.0 mg/kg per infusion). These increases were relatively long lasting, exceeding the time course of a mild withdrawal syndrome.

CONCLUSIONS

The DT5x10-day history of heroin self-administration resulted in an upward shift in the cocaine dose-effect curve, suggesting that DT5 heroin self-administration produced an increase in potency and sensitization of the maximal effectiveness with which cocaine functions as a reinforcer. The present experiments contribute to a growing amount of preclinical evidence suggesting an impact of opioid exposure on the reinforcing effects of cocaine, which may partially explain the high incidence of cocaine use in opioid-dependent individuals.

Do needle syringe programs reduce HIV infection among injecting drug users: a comprehensive review of the international evidence

This first international review of the evidence that needle syringe programs reduce HIV infection among injecting drug users found that conservative interpretation of the published data fulfills six of the nine Bradford Hill criteria (strength of association, replication of findings, temporal sequence, biological plausibility, coherence of evidence, and reasoning by analogy) and all six additional criteria (cost-effectiveness, absence of negative consequences, feasibility of implementation, expansion and coverage, unanticipated benefits, and application to special populations). The Bradford Hill criteria are often used to evaluate public health interventions. The principal finding of this review was that there is compelling evidence of effectiveness, safety, and cost-effectiveness, consistent with seven previous reviews conducted by or on behalf of U.S. government agencies. Authorities in countries affected or threatened by HIV infection among injecting drug users should carefully consider this convincing evidence now available for needle syringe programs with a view to establishing or expanding needle syringe programs to scale.

A Prognostic Model for HIV Seroconversion Among Injection Drug Users as a Tool for Stratification in Clinical Trials

OBJECTIVE

The main goal of this study was to construct a prognostic model for HIV seroconversion among injection drug users (IDUs) using easy-to-measure risk indicators.

DESIGN

Cox proportional hazards regression modeling was used for risk stratification in a heterogeneous population of IDUs with regards to HIV risk-taking behaviors.

METHODS

Subjects were recruited in a prospective cohort of IDUs followed between September 1992 and October 2001. A total of 1602 men, seronegative at enrollment with at least 1 follow-up visit, were included in the analyses. Only variables that consistently predict HIV seroconversion in several settings were considered. The final model was used to assign a risk score for each participant.

RESULTS

Three risk indicators were included in the risk score to predict HIV seroconversion: unstable housing, average cocaine injections per day, and having shared a syringe with a known HIV-positive partner. Kaplan-Meier survival functions were generated and risk score values stratified in 3 groups. HIV incidence rates per 100 person-years were as follows: 0.91 (95% CI, 0.55-1.52) for the low-risk group, 3.10 (95% CI, 2.49-3.84) for the moderate-risk group, and 7.82 (95% CI, 6.30-9.73) for the high-risk group (log-rank P value < 0.0001).

CONCLUSION

If validated in other settings, this risk score may improve the prediction of outcome and allow more accurate stratification in clinical trials.

Comparison of the reinforcing effects of cocaine and cocaine/heroin combinations under progressive ratio and choice schedules in rats

The co-use of cocaine and heroin is relatively common, with a growing clinical and preclinical literature dedicated to investigating the factors underlying the phenomenon. Specifically, several studies have compared the reinforcing effects of the coadministration of cocaine and heroin, referred to commonly as 'speedball', to either drug alone. The present study assessed whether addition of heroin to a wide range of cocaine doses produces reinforcing effects greater than cocaine alone using both a progressive ratio (PR) schedule and a choice procedure. Patterns of coadministration of cocaine and heroin offered simultaneously were also assessed using double-lumen cannulas. Under the PR schedule, speedball combinations across a range of doses (0.38-3.0 mg/kg/inf cocaine+1.5-48 microg/kg/inf heroin) did not support higher break points than cocaine alone. When cocaine and heroin were made available concurrently (ie on two separate levers), rats self-administered cocaine exclusively. Using a choice procedure, however, a preference was demonstrated for some speedball combinations (eg 0.18 mg/kg/inf cocaine+50 microg/kg/inf heroin; 0.38 mg/kg/inf cocaine+50 microg/kg/inf heroin) over cocaine alone (0.75 mg/kg/inf). So while results obtained using the PR schedule do not support the hypothesis that speedball combinations are more reinforcing than cocaine alone, data from the choice procedure do support this hypothesis. These apparently discrepant results demonstrate that these models are measuring different aspects of drug reinforcement, and suggest that choice procedures in rats provide a useful tool to study speedball self-administration.

Injection risk behavior among women syringe exchangers in San Francisco

Women who inject drugs in cities where syringe exchange programs (SEPs) are well established may have different risks for HIV infection. In 1997, we interviewed 149 female syringe exchangers in San Francisco, CA, a city with high rates of injection drug use that is home to one of the largest and oldest SEPs in the United States. In this report, we describe their sociodemographics, health, and risk behavior, and we examine factors associated with recent syringe sharing. Fifty percent of respondents were women of color and the median age was 38 years. Most (86%) injected heroin and nearly half were currently homeless or had recently been incarcerated. One-third of all women reported needle sharing in the prior month. This was higher than the rate of needle sharing reported by a mixed gender sample of San Francisco exchangers in 1993, although it resembled the rate reported by a mixed gender sample in 1992. In a multivariate analysis, syringe sharing was associated with age, housing status, and sexual partnerships. Syringe sharers were more likely to be young, homeless, or have a sexual partner who was also an injection drug user. While wide access to sterile syringes is an important strategy to reduce HIV transmission among injection drug users (IDU), syringe exchange alone cannot eradicate risky injection by female IDU. Additional efforts to reduce risky injection practices should focus on younger and homeless female IDU, as well as address selective risk taking between sexual partners.

Molecular epidemiologic analysis of hepatitis C virus infection in injecting drug users with acute hepatitis C in Japan

BACKGROUND AND AIM

The aim of this study was to examine whether particular hepatitis C virus (HCV) subtypes are spreading among injecting drug users (IDUs) in Yamaguchi prefecture, on the south-western tip of the island of Honshu in Japan, as found in European countries.

METHODS

We prospectively enrolled acute hepatitis C patients from January 2001 to March 2003. E2 gene sequences of HCV isolates from IDUs with acute hepatitis C were phylogenetically compared to those from 30 chronic hepatitis C patients with the same HCV subtypes who had or did not have a history of intravenous drug use.

RESULTS

Nine of 11 patients (82%) with acute hepatitis C were IDUs. The HCV subtypes were 2a in four and 2b in five, which contrasted with the high prevalence of subtype 1b in patients with chronic liver diseases in Japan. IDUs with acute hepatitis C (22.0 +/- 2.4 years old) were significantly younger than those with chronic hepatitis C (49.5 +/- 9.5 years old) for subtype 2a (P = 0.0005), but not for subtype 2b (25.6 +/- 5.4 vs 28.1 +/- 2.4 years old). Some HCV isolates of subtype 2b from IDUs with acute hepatitis C were phylogenetically related to those from IDUs with chronic hepatitis C. By contrast, there was no phylogenetic segregation of HCV in IDUs with subtype 2a. HCV isolates from non-IDUs were genetically divergent from each other and those from IDUs, irrespective of the HCV subtype.

CONCLUSION

Hepatitis C virus of the non-1b subtype, particularly subtype 2b, seemed to be transmitted between IDUs very recently in Yamaguchi prefecture, Japan.

Opportunities for prevention: hepatitis C prevalence and incidence in a cohort of young injection drug users

The objective of this study was to compare sociodemographic, drug, and sexual risk characteristics between hepatitis C virus (HCV) baseline positive and negative young (13-24 years) injection drug users (IDUs) and to determine prospective risk factors for HCV seroconversion among the youth. Data were collected through the Vancouver Injection Drug Users Study (VIDUS). To date, more than 1,400 Vancouver-area IDUs have been enrolled and followed up; 234 were aged 24 years and younger. Semiannually, participants have completed an interviewer-administered questionnaire and have undergone serologic testing for human immunodeficiency virus (HIV) and HCV. Univariate and multivariate logistic regression analyses were undertaken to investigate predictors of baseline HCV positivity. In the multivariate analyses, Cox regression models with time-dependent covariates were used to identify predictors of HCV seroconversion. Of the 232 young injectors, 107 (46%) were HCV positive at baseline and a further 37 HCV seroconverted during the study period for an incidence rate of 37.3 per 100 person-years. Baseline positivity was associated with Aboriginal ancestry, older age, greater number of years injecting drugs, recent incarceration, sex trade work, more than 100 lifetime sexual partners, a previous sexually transmitted disease, living in the IDU epicenter, and injection more than once per day of heroin, cocaine, and speedball. Factors independently associated with HCV seroconversion were having a partner who uses injection drugs, requiring help to inject, and injection of cocaine more than once daily. In conclusion, unlike older IDUs, more than one half of young injectors were HCV negative at recruitment. Thus, there is a window of opportunity for prevention. However, the incidence rate of HCV among these young IDUs is alarming, suggesting that the opportunity to intervene is exceedingly small.

Satellite needle distribution among injection drug users: policy and practice in two canadian cities

Access to clean needles and syringes through needle exchange programs (NEPs) has reduced both high-risk behaviors and the transmission of blood-borne infections among injection drug users (IDUs). However, policies regarding "needle-for-needle" exchange versus unrestricted needle distribution remain controversial. The objective of this study was to compare sources of needles, trends in needle distribution, and the practice of satellite needle distribution (SND) among IDUs in Vancouver and Montreal. SND was defined as receiving a new syringe from another individual through trading, purchasing, borrowing, or being given the syringe outright, or supplying a syringe to another individual through trading, selling, lending, or giving a syringe outright. This was practiced by 46% of IDUs in Vancouver and 50% of IDUs in Montreal. SND was associated with borrowing used injection equipment (adjusted OR [AOR], 2.62; 95% CI: 1.85-3.71), conducting bulk needle exchanges (AOR, 1.85; 95% CI: 1.34-2.54), being married or in a common-law relationship (AOR, 1.85; 95% CI: 1.34-2.54), and regular visits to the NEP (> weekly) (AOR, 1.54; 95% CI: 1.17-2.13). In Vancouver, SND was also associated with borrowing used needles (AOR, 2.07; 95% CI: 1.22-3.52). In these two cities, despite different distribution policies, almost half of the participants reported SND, and this was associated with high risk sharing. The practice of SND appears to be an important mechanism for needle acquisition, especially for those at highest risk for HIV and hepatitis C transmission.

HIV risk behaviors in African-American drug injector networks: implications of injection-partner mixing and partnership characteristics

AIMS

We explore the mechanisms by which 'partnership-level' variables--the mix of characteristics of individuals who inject drugs together--affect the incidence of HIV risk behaviors, including receptive syringe sharing, and facilitate or impede the spread of HIV.

DESIGN

We apply multivariate analysis techniques to data on injection partnerships (pairs of individuals who inject drugs together) collected using a network sample of 401 African-American IDUs in Washington, DC.

FINDINGS

Drug injectors tended to select injection partners of the same gender and similar age, but risk behaviors were most common in partnerships between individuals who are dissimilar in both gender and age. Partners who had a sexual relationship, injected drugs frequently together, smoked crack-cocaine regularly, injected speedball (heroin mixed with cocaine) regularly and/or had close social ties were more likely to engage in risky injection practices than otherwise similar partners. These factors account largely for the association between the gender-age mix of the partnership and injection risk behavior.

CONCLUSIONS

Among African-American IDUs in Washington DC, partnership-level variables appear critical in the transmission of HIV.

Females experiencing sexual and drug vulnerabilities are at elevated risk for HIV infection among youth who use injection drugs

OBJECTIVES

To compare sociodemographic, drug-related, and sexual risk variables between young (13-24 years of age) and older (> or =25 years of age) injection drug users (IDUs); and to determine HIV prevalence and associated risk factors for HIV infection among young IDUs.

METHODS

Data were collected through the Vancouver Injection Drug Users Study (VIDUS). To date, over 1400 Vancouver area IDUs have been enrolled and observed during follow-up. Sociodemographic, drug-related, and sexual risk variables were compared between younger and older IDUs using nonparametric methods. Mantel-Haenszel and logistic regression methods were used to compare HIV-positive and HIV-negative female youth.

RESULTS

Younger injectors (N = 232) were more likely to be female; work in the sex trade; report condom use; inject heroin daily; smoke crack cocaine daily; and need help injecting. HIV prevalence at baseline among the youth was 10%. HIV prevalence was associated with female gender; history of sexual abuse; engaging in survival sex; injecting heroin daily; injecting speedballs (a mixture of heroin and cocaine) daily; and having numerous lifetime sexual partners.

CONCLUSION

Our data show that HIV positivity among young IDUs is concentrated among females engaged in dual sexual and drug-related risk exposure categories. Over half the HIV-positive youth were Aboriginal (a classification used by the federal government in Canada to include native peoples of all ethnic groups). Targeted interventions that take into account sexual and drug risk for young female and Aboriginal peoples are urgently needed.

Large decline in injecting drug use in Amsterdam, 1986-1998: explanatory mechanisms and determinants of injecting transitions

OBJECTIVES

To study community wide trends in injecting prevalence and trends in injecting transitions, and determinants.

DESIGN

Open cohort study with follow up every four months (Amsterdam Cohort Study). Generalised estimating equations were used for statistical analysis.

SETTING

Amsterdam has adopted a harm reduction approach as drug policy.

PARTICIPANTS

996 drug users who were recruited from 1986 to 1998, mainly at methadone programmes, who paid 13620 cohort visits.

MAIN RESULTS

The prevalence of injecting decreased exponentially (66% to 36% in four to six monthly periods). Selective mortality and migration could maximally explain 33% of this decline. Instead, injecting initiation linearly decreased (4.1% to 0.7% per visit), cessation exponentially increased (10.0% to 17.1%), and relapse linearly decreased (21.3% to 11.8%). Non-injecting cocaine use (mainly pre-cooked, comparable to crack) and heroin use strongly increased. Trends were not attributable to changes in the study sample.

CONCLUSIONS

Harm reduction, including large scale needle exchange programmes, does not lead to an increase in injecting drug use. The injecting decline seems mainly attributable to ecological factors (for example, drug culture and market). Prevention of injecting is possible and peer-based interventions may be effective. The consequences of the recent upsurge in crack use requires further study.