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Introduction Concomitant opioid abuse is a serious problem among patients receiving methadone maintenance treatment (MMT) for opioid use disorder. This is an exploratory study that aims to identify predictors of the length of time a patient receiving MMT for opioid use disorder remains abstinent (relapse-free). Methods Data were collected from 250 MMT patients enrolled in addiction treatment clinics across Southern Ontario. The impact of certain clinical and socio-demographic factors on the outcome (time until opioid relapse) was determined using a Cox proportional hazard model. Results History of injecting drug use behavior (hazard ratio (HR): 2.26, P = 0.042), illicit benzodiazepine consumption (HR: 1.07, P = 0.002), and the age of onset of opioid abuse (HR: 1.10, P < 0.0001) are important indicators of accelerated relapse among MMT patients. Conversely, current age is positively associated with duration of abstinence from illicit opioid use, serving as a protective factor against relapse (HR: 0.93, P = 0.003). Conclusion This study helps to identify patients at increased risk of relapse during MMT, allowing health care providers to target more aggressive adjunct therapies toward high-risk patients.

Background While a number of pharmacological interventions exist for the treatment of opioid use disorder, evidence evaluating the effect of pain on substance use behavior, attrition rate, and physical or mental health among these therapies has not been well established. We aim to evaluate these effects using evidence gathered from a systematic review of studies evaluating chronic non-cancer pain (CNCP) in patients with opioid use disorder. Methods We searched the Medline, EMBASE, PubMed, PsycINFO, Web of Science, Cochrane Database of Systematic Reviews, ProQuest Dissertations and theses Database, Cochrane Central Register of Controlled Trials, World Health Organization International Clinical Trials Registry Platform Search Portal, and National Institutes for Health Clinical Trials Registry databases to identify articles evaluating the impact of pain on addiction treatment outcomes for patients maintained on opioid agonist therapy. Results Upon screening 3,540 articles, 14 studies with a combined sample of 3,128 patients fulfilled the review inclusion criteria. Results from the meta-analysis suggest that pain has no effect on illicit opioid consumption [pooled odds ratio (pOR): 0.70, 95%CI 0.41–1.17; I 2 = 0.0] but a protective effect for reducing illicit non-opioid substance use (pOR: 0.57, 95%CI 0.41–0.79; I 2 = 0.0). Studies evaluating illicit opioid consumption using other measures demonstrate pain to increase the risk for opioid abuse. Pain is significantly associated with the presence of psychiatric disorders (pOR: 2.18; 95%CI 1.6, 2.9; I 2 = 0.0%). Conclusion CNCP may increase risk for continued opioid abuse and poor psychiatric functioning. Qualitative synthesis of the findings suggests that major methodological differences in the design and measurement of pain and treatment response outcomes are likely impacting the effect estimates.