Dropouts due to Inadequate Dosing: Greater than 50% of Patients

More than 50% of patients treated with methadone or buprenorphine drop out of treatment, mostly with lower than recommended doses, a recent study conducted in Canada has found.

For the study, records of patients with opioid use disorder (OUD) who were treated with methadone (73.9% of patients), buprenorphine (24.7%) or slow-release morphine (1.4%) (legal in Canada) were studied.

Less than 60% of patients completed the induction phase, and about 50% of patients dropped out during the maintenance phase of treatment.

Those most likely to drop out were receiving the minimum effective dose: 60 mg/day of methadone, or 12 mg a day for buprenorphine.

“Our findings indicate the distinction of these outcomes is clinically important given the exceptionally high discontinuation rate observed during induction,” the researchers write in “Assessing the determinants of completing OAT [opioid agonist treatment] induction and long-term retention: A population-based study in British Columbia, Canada,” published in the Journal of Substance Abuse Treatment by Megan Kurz and colleagues. The researchers noted that there is little known about what causes dropouts. “A dearth of evidence exists exploring motivations to discontinue OAT,” the researchers wrote.

There were additional findings of note in the British Columbia study:

  • Individuals with a higher chronic disease score had longer times to discontinuation and a greater likelihood of completing induction, suggesting a positive effect from health care engagement.
  • Diagnosed mental health conditions were associated with lower discontinuation rates, which also suggest a positive effect from health care engagement (in this study, 73% of OAT patients had a diagnosed mental disorder).
  • About one-third of the patients in the sample had been or were currently incarcerated at OAT initiation, and those currently incarcerated had 31% higher odds of completing induction, suggesting that incarceration is a conducive setting for treatment.

What would help would be more continuity of care, especially considering the elevated risk of overdose deaths following release from correctional facilities, the researchers wrote.

Also more likely to drop out: individuals without stable housing. This is consistent with other studies showing that people without stable housing have less successful engagement with health care, the researchers wrote. “Our finding of higher discontinuations and lower odds of completing induction at community health centers (CHCs) — which are low-threshold services aiming to improve chronic disease management and provide comprehensive care — similarly reflects greater levels of instability within the client base,” the researchers wrote. They add that these findings should acknowledge that CHCs provide greater accessibility that reaches clients who may not otherwise have health care providers. Still, housing instability has “deleterious impacts,” including the concomitant incarceration, alcohol use disorder and lack of comprehensive care.

Limitations of the study included:

  • As in any observational study, there were possible unmeasured confounding effects, meaning the links could not be interpreted as causal.
  • The administrative nature of the data used in this study may be subject to misclassification in terms of unstable housing and tobacco history (which is mostly identified through medications prescribed to treat nicotine addiction).
  • The analysis occurred in the context of British Columbia’s low-threshold care model, in which primary care physicians can prescribe both methadone and buprenorphine which are dispensed through pharmacies, making the study less generalizable to systems like that in the United States that have more restrictions with treatment with methadone.

The study was funded by the Health Canada Substance Use and Addiction Program and the U.S. National Institute on Drug Abuse.

References:

Kurz M, Min JE, Dale LM, Nosyk B: Assessing the determinants of completing OAT induction and long-term retentions: A population-based study in British Columbia, Canada.

Assessing the determinants of completing OAT induction and long-term retention: A population-based study in British Columbia, Canada. J Subst Abuse Treat. . 2022 Feb;133:108647.
doi: 10.1016/j.jsat.2021.108647. Epub 2021 Oct 26.

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