Increases in the availability of prescribed opioids in a Canadian setting

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Abstract

Background

The nonmedical use of prescribed opioids (POs) has increased across North America over the past decade. Our objective was to identify changes in the availability of POs and other illicit drugs among drug users in a Canadian setting.

Methods

Information on the availability of illicit drugs was collected in standardized interviews from a large observational research program involving illicit drug users in Vancouver, British Columbia from 2006 to 2010. The primary outcome was the perceived availability of a set of six POs (aspirin/oxycodone, hydromorphone, oxycodone, morphine, acetaminophen/codeine and methadone) among individuals reporting ever using POs. Availability was measured in three levels: not available, delayed availability (available ≥10 min), and immediate availability (available <10 min). Multivariate ordinal logistic regression models were executed to estimate the trend in PO availability, controlling for individual characteristics hypothesized to influence availability.

Results

1871 individuals were followed during the study period (2006–2010), including 583 (31.2%) women. The availability of POs increased over time, regardless of changes in the characteristics of cohort entrants. These increases were observed while the availability of traditional drugs of abuse (e.g., heroin and cocaine) remained constant. The adjusted odds of delayed availability vs. unavailability were between 34% (hydromorphone) and 71% (acetaminophen/codeine) greater in each calendar year.

Discussion

The availability of POs among drug users in a Canadian setting increased markedly over a relatively short timeframe, despite persistent and high availability of heroin and cocaine. Further study is required to determine the context of use of POs, associated harms, as well as policy responses to increasing availability.

Introduction

Whereas the 1980s and 1990s bore witness to epidemics of crack cocaine and heroin use in many inner city areas, the nonmedical use of prescribed opioids (POs) is emerging as an increasing concern. Rising rates of use have been documented in the US, most notably among youth and young adults. Among high school seniors, Hydrocodone abuse was second only to marijuana abuse (Volkow and McLellan, 2011). A 7-fold increase in drug treatment admissions involving opioids other than heroin was observed between 1998 and 2009 (SAMHSA TEDS Database, 2011). Emergency department visits involving non-medical use of prescription drugs increased to a greater extent than other illicit drugs, with Oxycodone (175,949 in 2009; a 242.2% increase from 2004) and Hydrocodone (104,490 in 2009; a 124.5% increase from 2004) among the highest increases. Finally prescribed opioid-related overdose deaths increased from 2000 in 1999 to 14,800 in 2008 (Centers for Disease Control and Prevention, 2011). Opioid overdose is now the second leading cause of unintentional death in the United States, second only to motor vehicle accidents (National Centre for Injury Prevention and Control, 2010), which prompted the Centers for Disease Control and Prevention to label PO overdose as a national epidemic (Centers for Disease Control and Prevention, 2011).

There is accumulating evidence of similar trends in use in Canadian settings. An early study conducted in Vancouver identified a range of prescription medications available for illicit sale, including POs such as acetaminophen/codeine, aspirin/oxycodone, meperidine, hydromorphone, morphine, and Anileridine (no longer manufactured in North America; Sajan et al., 1998). In a 2004 report on a cohort of methadone maintenance treatment (MMT) patients in Ontario, Brands et al. (2004) reported that 83% of all patients had been using POs, with or without heroin, upon admission. The OPICAN study, conducted in five Canadian cities, revealed that nonmedical use of POs was far more prevalent than the use of heroin in every setting except Vancouver and Montreal (Fischer et al., 2005). From 2002 to 2005, a relative increase of 24% was observed in the proportion of the street drug using population who used non-medical POs only (Popova et al., 2009). Recent studies have described increases in the amounts of opioids prescribed across Canada (Fischer et al., 2011), increasing opioid utilization among recipients of social assistance in Ontario (Gomes et al., 2011a) and street users in Montreal (Bruneau et al., 2012, Roy et al., 2011), a strong independent relationship between PO dose and opioid-related mortality (Gomes et al., 2011b), high variation in opioid prescribing among Ontario physicians (Dhalla et al., 2011) and high rates of non-methadone opioid use among clients in methadone maintenance treatment in Ontario (Kurdyak et al., 2011).

Despite this rapidly growing literature documenting problematic PO use in North America, few studies have endeavored to ascertain temporal trends in street-level availability of POs and other illicit drugs (e.g., cocaine and heroin). Our objective, therefore, was to examine the availability of prescribed opioids and other illicit drugs among street users in Vancouver, British Columbia between 2006 and 2010.

Section snippets

Study design

Data for this analysis were derived from the baseline assessments of a series of ongoing open prospective cohort studies involving illicit drug users, including the At-Risk Youth Study (ARYS), the AIDS Care Cohort to evaluate Exposure to Survival Services (ACCESS), and the Vancouver Injection Drug Users Study (VIDUS). The VIDUS study began enrollment in May 1996 and recruits individuals through word of mouth, street out-reach, and referrals. Recently, the original VIDUS cohort was divided into

Summary statistics

Summary statistics on the covariates included in the analysis are provided in Table 1. A total of 1871 individuals were recruited into the ARYS [N = 712 (38.1%)], ACCESS [N = 536 (28.7%)] and VIDUS [N = 623 (33.3%)] cohorts during the study period; 31% were female and 37% were 25 or under (median age: 33.7; interquartile range: 22.7, 44.3). The majority of individuals reported living in unstable housing (52%), 37.8% reported dealing drugs and 8.3% reported being engaged in sex work in the past 6

Discussion

Among illicit drug users in Vancouver, Canada, the immediate availability of POs increased significantly from 2006 to 2010. These increases persisted after adjustment for changes in the characteristics of individuals entering the cohorts under study. Our finding suggesting increased presence of POs within illicit drug markets is consistent with a diverse set of studies undertaken in North America indicating rising PO use (Volkow and McLellan, 2011, Fischer et al., 2005, Popova et al., 2009,

Role of funding source

Funding for this study was provided by National Institutes of Health (NIH) grants R01-DA011591, R01-DA031727-01 and a Canadian Institutes of Health Research (CIHR) grant RAA-79918. Thomas Kerr is supported by a Scholar Award from the Michael Smith Foundation for Health Research (MSFHR) and an Investigator Award from the CIHR. Bohdan Nosyk is a CIHR Bisby Fellow, and also supported by a postdoctoral fellowship from the Michael Smith Foundation for Health Research. Brandon Marshall is supported

Contributors

Authors BN, EW and TK and BF designed the study protocol. BN wrote the first draft of the manuscript. BN undertook the statistical analysis with significant scientific input from BDLM and TK. TK, EW and JSGM were responsible for data collection. All authors contributed to and have approved the final manuscript.

Conflict of interest

All authors declare that they have no conflicts of interest.

Acknowledgements

The authors thank the study participants for their contribution to the research, as well as current and past investigators and staff. We would like to thank Deborah Graham, Peter Vann, Caitlin Johnston, Steve Kain, and Calvin Lai for their research and administrative assistance.

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