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Factors associated with willingness to participate in a pharmacologic addiction treatment clinical trial… Uhlmann, Sasha; Milloy, M-J; Ahamad, Keith; Nguyen, Paul; Kerr, Thomas; Wood, Evan; Richardson, Lindsey Jun 1, 2016

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FACTORS ASSOCIATED WITH WILLINGNESS TO PARTICIPATE IN A PHARMACOLOGIC ADDICTION TREATMENT CLINICAL TRIAL AMONG ILLICIT DRUG USERS    Sasha Uhlmann, MD, MPH ’1 MJ Milloy, PhD’1 Keith Ahamad, MD’1 Paul Nguyen, PhD;1 Thomas Kerr, PhD;1,2 Evan Wood, MD, PhD;1,2  Lindsey Richardson, DPhil1  1. British Columbia Centre for Excellence in HIV/ AIDS, St. Paul’s Hospital, 608 – 1081 Burrard  Street, Vancouver, B.C., Canada. V6Z 1Y6  2. Division of AIDS, Department of Medicine, University of British Columbia, 2775 Laurel Street, 10th Floor, Vancouver, B.C., Canada. V5Z 1M9   Running Head: Willingness to Participate in Addiction Treatment Trials   Send correspondence to: Lindsey Richardson, DPhil Assistant Professor, Department of Sociology University of British Columbia  608 - 1081 Burrard  St Vancouver, BC, V6Z 1Y6 Tel: 604-682-2344 X 66878. Fax: 604-806-9044 Email: uhri-lr@cfenet.ubc.ca  Abstract: 250 Narrative: 2176 Number of Tables: 2 Number of Figures: 0 Number of References: 50  ABSTRACT Background and Objectives: Although new medications are needed to address the harms of drug addiction, rates of willingness to participate in addictions treatment trials among people who use drugs (PWUD) have not been well characterized .  Methods: One thousand twenty PWUD enrolled  in two community-recruited cohorts in Vancouver, Canada, were asked  whether they would  be willing to participate in an addiction treatment trial. Logistic regression was used  to identify factors independently associated  with a willingness to participate.  Results: Among the 1,020 illicit d rug users surveyed between June 1, 2013 and  November 30, 2013, 58.3% indicated  a willingness to participate. In multivariate analysis, factors independently associated  with a willingness to participate in an addiction treatment trial, included: daily heroin injection (Adjusted  Odds Ratio [AOR] = 1.75 [95% Confidence Interval [CI]: 1.13 -2.72]); daily crack smoking (AOR = 1.81 [95% CI: 1.23 – 2.66]); sex work involvement (AOR = 2.22 [95% CI: 1.21 - 4.06]); HIV seropositivity (AOR = 1.49 [95% CI: 1.15 – 1.94]); and  methadone maintenance therapy participation (AOR = 1.77 [95% CI: 1.37 – 2.30]).  Discussion and Conclusions: High rates of willingness to participate in an addiction treatment trial were observed  in this setting. Imp ortantly, high-risk drug and  sexual activities were positively associated  with a willingness to participate, which may suggest a desire for new treatment interventions among illicit d rug users engaged in high-risk behaviour.   Scientific Significance: These results highlight the viability of studies seeking to enroll representative samples of illicit d rug users engaged in high -risk drug use.  INTRODUCTION  Addiction medicine is a rapid ly expanding area of clinical practice and  medical research. The United  States National Institutes of Health (NIH) estimated  that in 2013, over 4.1 billion dollars were spent on substance abuse research in the U.S.1 An active area in this field  is the development and  testing of new medications to treat problematic drug use. In the past few years, methadone, buprenorphine and  naltrexone (including extended release formulations) have been extensively examined for the treatment of opioid  use d isorders and  have all emerged  as effective treatment options.2-5 These medications have been shown to decrease illicit opioid  use, and  to varying degrees decrease several of the health and  social harms associated  with opioid  addiction, such as human immunodeficiency virus (HIV) transmission and  risk behaviors, hepatitis C virus transmission, risky sexual practices and  arrest and  imprisonment .2,4-12 Unfortunately, current pharmacologic treatment options for stimulant dependence (e.g., cocaine and  amphetamine type stimulants) are lacking 13-16, and  evidence-based  therapies are desperately needed to reduce the health and  social harms associated  with stimulant use.17,18  The National Institute on Drug Abuse (NIDA) has developed the Clinical Trials Network in an attempt to provide rigorous testing of new addiction pharmacotherapies.19 However, NIDA studies have generally recruited  research participants from community treatment programs, suggesting that out -of-treatment drug users may be underrepresented  in treatment studies to date. Recruiting out-of-treatment patients for clinical trials may be challenging as they may have little interaction with the health care system, may d istrust medical practitioners and  researchers and/ or research, or may have co-morbid  medical or psychiatric conditions that preclude them from research participation.20-22 There is also the issue of excluding willing research subjects from studies where presumed non-compliance may resu lt in them not being enrolled  in clinical trials.23 Since little is known regard ing willingness to participate or factors associated  with willingness to participate in pharmacologic addictions treatment trials among community recruited  samples of drug users, the present study was conducted  with a cohort of persons who use illicit d rugs to assess the prevalence of willingness to participate, and  factors associated  with willingness to participate in a randomized  control trial (RCT) for addiction treatment.  METHODS Data for this study were derived  from the Vancouver Injection Drug Users Study (VIDUS), and  AIDS Care Cohort to Evaluate Access to Survival Services (ACCESS), open prospective cohorts of HIV-seronegative individuals (VIDUS) who inject drugs, or HIV-seropositive individuals (ACCESS) who use illicit d rugs, in Vancouver, Canada.  The design of both studies has previously been described  in detail.17,24  Briefly, participants were eligible for the study if they were 18 years or older, injected  or used  illicit d rugs other than marijuana within the past month, resided  in the Greater Vancouver Region, and  provided  written informed consent. Participants were recruited  through extensive street -based  outreach methods and  snowball sampling beginning in  May 1996. At baseline and  every six months thereafter, participants completed  an interviewer -administered  questionnaire that elicited  information regard ing socio -demographic characteristics, d rug use, HIV risk behaviours and  addiction treatment utilization. Participants received  $20 CAD remuneration for each visit. Both the VIDUS and ACCESS studies recruitment and  follow up procedures are identical, with the exception of questions specific to HIV infection in the ACCESS questionnaire, so as to enable pooled  analyses. Both the VIDUS and ACCESS studies were approved by the Research Ethics Board  of Providence Health Care/ University of British Columbia.  For the primary analysis, a new question was added to the questionnaire in June 2013, and  responses to the question were gathered  from June 1, 2013 to November 30, 2013.  The question assessed  whether participants were willing to participate in an RCT for drug treatment by asking, “If a new medication was being developed that might help you cut down on your drug  use, would  you be interested  in enrolling in a clinical trial to test it? You would be regularly assessed  by an addiction doctor and  would  provide urine samples for drug testing.” The definition of an RCT was provided , if needed to ensure understanding, and participants could  answer “yes” or “no” and  a follow up question for those responding “no” provided  several response options inquiring about the reasons for their negative response. Participants who answered , “yes” were compared  to those who answered  “no” on a priori selected  demographic, behavioural and  drug use variables, hypothesized  to be associated  with a willingness to participate based  on previous research .25,26 These variables included: age (per year older); female gender (yes vs. no); ethnicity (Caucasian vs. other); daily heroin injection (yes vs. no); daily cocaine injection (yes vs. no); daily crack smoking (yes vs. no); homelessness (yes vs. no); involvement in sex work, defined  as exchanging sex for money, gifts, food , shelter, clothes, drugs or other (yes vs. no); HIV seropositivity (yes vs. no); participation in methadone maintenance therapy (MMT) (yes vs. no); or participation in drug treatment, defined  as alcohol and/ or drug treatment other than MMT (yes vs. no). All behavioural and  drug risk characteristics refer to the six-month period  prior to the interview.  All variable definitions were identical to those used  extensively in prior analyses.27,28   We used  bivariate and  multivariate logistic regression analyses to determine factors associated  with the willingness to participate in an RCT. To adjust for potential confounding and  identify the independent correlates  of willingness to participate in an RCT, only variables that had  a p-value < 0.10 in the bivariate analyses were considered  in the full multivariate model. Using the backwards model selection procedure, we constructed  the final multivariate model with the best fit, as ind icated  by the lowest AIC value.29 All statistical analyses were performed using the SAS software version 9.3 (SAS, Cary, NC, USA). All p-values are two sided .  RESULTS Between June 1, 2013 and  November 30, 2013, observations from 1,020 VIDUS and ACCESS participants were included in the present analysis. Among these individuals, median age was 48 years (Inter-quartile range [IQR]: 42 – 54), 345 (33.8%) were female and  576 (56.5%) were Caucasian. Of the 1,020 participants recruited into VIDUS and ACCESS, 595 (58.3%) indicated  a willingness to participate in an RCT. As shown in Table 1, the following behavioural and  drug risk characteristics were significantly associated  with a willingness to participate: daily heroin injection (Odds Ratio [OR] = 1.97 [95% Confidence Interval [CI]: 1.30 -3.00]); daily crack smoking (OR = 2.20 [95% CI: 1.51 – 3.20]); homelessness (OR = 1.53 [95% CI: 1.03 – 2.26]); sex work (OR = 2.84 [95% CI: 1.58 – 5.09]); HIV seropositivity (OR = 1.34 [95% CI: 1.04 – 1.73]); and MMT participation (OR = 1.74 [95% CI: 1.35 – 2.24]) (all p-value < 0.05).  The results of the multivariate analysis are presented  in Table 2. The following factors were significantly and  independently associated  with a willingness to participate in an RCT: daily heroin injection (Adjusted  Odds Ratio [AOR] = 1.75 [95% CI: 1.13 -2.72]); daily crack smoking (AOR = 1.81 [95% CI: 1.23 – 2.66]); sex work involvement (AOR = 2.22 [95% CI: 1.21 - 4.06]); HIV seropositivity (AOR = 1.49 [95% CI: 1.15 – 1.94]); and  MMT participation (AOR = 1.77 [95% CI: 1.37 – 2.30]).  DISCUSSION   In the present study, we found high rates of willingness to participate in a pharmacologic addiction treatment RCT among a community-recruited  cohort of illicit d rug users. We also found that willingness to participate was significantly associated  with daily heroin injection, daily crack smoking, sex work involvement, HIV seropositivity and  MMT participation. To our knowledge, this is the first study to examine willingness to participate in a  pharmacologic addictions treatment RCT among a community-recruited  sample of illicit d rug users.  Although there is a paucity of research regard ing willingness to participate in pharmacologic addictions treatment trials, a body of literature exists regard ing drug users willingness to participate in HIV and hepatitis C trials.24,30-34 In a cohort of injection drug users, 56% were willing to participate in an HIV vaccine trial.34 Among young injection drug users surveyed to participate in a hepatitis C vaccine study, 67% and 43% were willing to participate in a 1 and  4-year study, respectively.31 Taken together, these numbers are comparable to the rates observed  in our study (58.3%). Fry et al showed that motivations for research involvement among drug users was multi-d imensional, and  included  economic gain, altruism, activism and information seeking, among others.32  Our study found that daily injection heroin use and  non -injection crack cocaine use were associated  with willingness to participate in a  pharmacologic addiction treatment RCT. This is similar to a study by Miller et al, which found  that frequent heroin injection among injection drug users was associated  with a willingness to participate in a heroin prescription program .26 This may reflect that active daily users have failed  other pharmacologic treatment options and  are interested  in exploring new therapies. Although several pharmacologic options already exist for the treatment of opioid addiction, including methadone, buprenorphine, and  extended release naltrexone,2,4,5,7,8,35 these options do not sustain abstinence in all users,36 necessitating continued  research into new medications and  d ifferent formulations of existing ones. No approved pharmacologic treatment options presently exist for stimulant use d isorders14-16 and  it is therefore unsurprising that ind ividuals engaged in frequent crack-cocaine use would  be eager to participate in drug treatment trials. Developing new medical treatments for stimulant addiction, including crack -cocaine, is a major public health priority given the health and  social harms associated  with crack-cocaine use.37-40 It is therefore encouraging that these individuals are willing to participate in new trials.  In our study, HIV seropositivity was associated  with a willingness to participate. Increasing enrollment of HIV positive persons from vulnerable populations into clinical trials is a current priority of HIV research .41,42 This focus may increase the likelihood that HIV positive persons are willing to participate in other types of clinical trials.  It is also possible that their frequent contact with the health care system, or enrollment in previous HIV medicine trials, makes them amenable to participating in addiction treatment RCTs. Doab et al. showed that illicit d rug users who were trial experienced  had  better understanding of clinical trial concepts and  were more likely to find  those concepts acceptable.33 Whether previous participation in an RCT makes individuals more, or less willing to participate in subsequent trials is an area of potential future research. While we have identified  subgroups of illicit d rug users that may be more likely to participate in RCTs, developing specific recruitment strategies is beyond the scope of the current analysis. This will be an important area of research as pharmacologic addictions treatment RCTs move forward . As well, developing effective treatments for illicit d rug users at varying levels of dr ug use intensity remains an important priority. Future RCTs could  prioritize recruiting participants across varying levels of use, and d ifferent strategies may be needed for each group. Illicit d rug users remain a heterogeneous group and  having a d iverse sample to participate in RCTs would  increase the generalizability of new pharmacotherap ies found to be effective. This study has limitations. As our study sample was generated  through street-based  recruitment methods, generalizing our findings to other populations of illicit d rug users requires caution. However, it is noteworthy that the cohort demographics are similar to other local and  international studies of injection drug users 43-46. Secondly, as our outcome of interest was willingness to participate in a hypothesized  trial it is possible that recruitment into an actual clinical trial may result, as in previous research, in lower levels of willingness to participate 47. However, a recent study among participants in the VIDUS cohort found that reported  willingness measures predicted  subsequent use of a safe injecting facility, and  that measures of willingness measures in this population were a valid  tool 25. The development of several new addiction treatment RCTs in the study area will allow us to determine whether a d ifference exists between hypothesized  and  actual recruitment. Third ly, socially desirable responding is a concern in studies of marginalized  populations 48. Although interviewers were trained  to build  trust and  rapport with participants, and  confidentiality is assured , it is possible we overestimated  the percentage of individuals willing to participate.  Also, previous studies have reported  that ind ividuals are less willing to participate in an RCT when more details, such as randomization, are provided  49,50. Although more details were provided  to participants if necessary, it is possible that a detailed  description of RCT methodology would  result in less willingness to participate. Finally, it is possible that the motivation to enroll in an RCT is for financial compensation and  not to seek new drug treatments. This factor was not assessed  in our study but is an important area of future research. Importantly, participant’s motivation to change and  participant’s perceived  drug use severity were not assessed  in this study. It is possib le that participants with the highest perceived drug use severity are more motivated to change drug use practices. It is also possible that participants who are more motivated  to change are more likely to participate in pharmacologic RCTs. Future analyses in this, and  other populations of illicit d rug users, could  assess whether perceived severity of drug use translates into motivation to change, and  whether motivation to change predicts subsequent enrollment in pharmacologic RCTs. Although some odds ratios are modest, they nevertheless represent statistically significant findings. Given the lack of research in this area, it is unclear whether these results represent clinically meaningful effect sizes. Examinations of enrollment patterns as pharmacologic add iction treatment RCTs begin enrolling participants in the current and  other study sites will provide the means to assess whether there is actual increased  enrollment by the out -of-treatment populations identified  in our study. In summary, the present study found high rates of willingness to participate in an pharmacologic addiction treatment RCT among community-recruited  illicit d rug users and  that willingness was associated  with daily heroin injection and  daily crack smoking, sex work involvement, HIV seropositivity and  MMT participation. These findings appear to highlight both the desire for new drug treatment strategies among high-risk drug users and  the feasibility of studies seeking to enroll participants from populations of high-risk drug users. The levels of willingness in the current study underscore the importance of focusing addiction pharmacotherapy trials on a broad  range of drug using populations, including out-of-treatment and  high-risk drug users.    Acknowledgements:  This study was supported  by the US National Institutes of Health (R01DA011591) (R01DA021525) and  the Canadian Institutes for Health Research (MOP-79297) through the Canadian Research Initiative on Substance Misuse (SMN- 139148). Neither institution had  any role in the study design , collection, analysis and  interpretation of the data, writing of the report or the decision to submit the paper. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program through a Tier 1 Canada Research Chair in Inner City Medicine which supports Dr Evan Wood. Lindsey Richardson is supported  by a Michael Smith Foundation for Health Research Career Scholar Award . The authors thank the study participants for their contribution to the research, as well as current and  past researchers and  staff.  Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and  writing of this paper. 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