Assessing the Potential of Oral Opioid Agonist Treatment to Prevent Injection Drug Use Initiation Assistance Provision in People Who Inject Drugs
Bibliographic record
Abstract
Injection drug use is a significant risk factor for morbidity and mortality from overdose and injection-related infections. Most first-time injections involve assistance from experienced people who inject drugs (PWID), with frequent injecting and withdrawal associated with assistance provision. Initial cross-sectional data suggests that first-line oral opioid agonist treatment (OAT) with methadone or buprenorphine/naloxone for opioid use disorder may reduce the likelihood that PWID facilitate first injections. This thesis evaluates whether available oral OAT medications in Canada can prevent injection initiation assistance provision in PWID. I first validated common questionnaire-based measures of current and recent first-line OAT enrollment in a sample of PWID in Toronto, relative to prescription dispensation claims data. Both self-reported measures were relatively accurate, though participants tended to underreport recent treatment and overreport current treatment. Using marginal structural models, I then analyzed questionnaire data from December 2014-May 2018 to assess whether current first-line OAT reduces the short-term risk of providing injection initiation assistance in a cohort of Vancouver-based PWID with frequent non-medical opioid use. Participants on first-line OAT (versus no OAT) were 50% less likely, on average, to help someone initiate injecting in the following six months. However, the corresponding 95% confidence interval (0.23-1.11) was imprecise due to small sample size, outcome rarity, and a weaker effect in people with daily baseline opioid injecting. Adjusting for self-reported treatment misclassification yielded comparable results. Lastly, I conducted a prevalent new-user cohort study using questionnaire data from June 2017-March 2020 on Vancouver-based PWID to evaluate the effectiveness of OAT with slow-release oral morphine (SROM) on non-medical opioid injecting and injection initiation assistance provision versus first-line OAT. After matching to reduce confounding, recent SROM initiation was not associated with a differential likelihood of daily non-medical opioid injecting or providing injection initiation assistance over the same six-month period in new users. Collectively, these findings provide additional support for oral OAT as prevention against injection initiation assistance provision in PWID, while reinforcing a need for alternative medications for those who have not adequately benefitted from previous oral OAT. Further research could explore the impact of higher-intensity injectable OAT on injection initiation assistance provision.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.009 | 0.053 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".