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.
Keywords: methadone; opioid relapse; opioid substitution treatment; opioid use disorder; substance abuse.