title: J-shaped relationship between supervised methadone consumption and retention in methadone maintenance treatment (MMT) in primary care: National cohort study.
abstract: Supervised consumption ensures patients take methadone as prescribed and prevents diversion, however, the influence of supervised consumption on retention is unclear. We examined association between supervised consumption and retention across multiple treatment episodes.
  
  
  
  Cohort study of persons experiencing ≥1 MMT episodes in primary care (2004-2010), excluding ongoing episodes at the start of follow-up. Length of treatment episodes based on methadone prescriptions, retention classified as no interruption in prescribed methadone lasting >7 days. When a patient did not receive a new prescription within seven days after the end of coverage of a prescription, they were considered to have ceased treatment. We evaluated the relationship between supervised consumption and time to discontinuation of treatment using proportional hazards gamma frailty models to account for recurrent MMT episodes. Age, gender, median daily methadone dose, and comorbidities included as potential confounders.
  
  
  
  6393 patients experienced 19,715 treatment episodes over the six-year follow-up period. A J-shaped relationship was observed; having between 20 and 60% of methadone scripts supervised (compared to <20%) associated with reduced time to discontinuation (20-39% HR=0.88, 95% CI 0.81-0.95; 40-59%: HR=0.87, 95% CI 0.81-0.94). Beyond a threshold of 60%, retention reduced (60-79% of scripts: HR=1.28, 95% CI 1.20-1.36;>80% of scripts: HR=3.59, 95% CI 3.38-3.81). Median daily dose between 60 and 120mg/per day, and multiple treatment episodes also associated with longer time to discontinuation of treatment.
  
  
  
  A J-shaped relationship was observed between supervised consumption and retention in treatment. Additionally, patients experiencing multiple treatment episodes tend to stay in treatment for progressively longer periods of time.
authors.affiliation: School of Pharmacy, Royal College of Surgeons in Ireland, 123 Stephen's Green, Dublin 2, Ireland. Electronic address: gcousins@rcsi.ie.
authors.forename: Gráinne
authors.initials: G
authors.lastname: Cousins
authors.affiliation: HRB Centre for Primary Care Research, Royal College of Surgeons in Ireland, 123 Stephen's Green, Dublin 2, Ireland.
authors.forename: Fiona
authors.initials: F
authors.lastname: Boland
authors.affiliation: Trinity College Centre for Health Sciences, Tallaght Hospital, Dublin 24, Ireland.
authors.forename: Joseph
authors.initials: J
authors.lastname: Barry
authors.affiliation: Health Research Board, Lower Mount Street, Dublin 2, Ireland.
authors.forename: Suzi
authors.initials: S
authors.lastname: Lyons
authors.affiliation: Addiction Services, Health Services Executive, Dublin, Ireland.
authors.forename: Eamon
authors.initials: E
authors.lastname: Keenan
authors.affiliation: Addiction Services, Health Services Executive, Dublin, Ireland.
authors.forename: Denis
authors.initials: D
authors.lastname: O'Driscoll
authors.affiliation: Division of Population Health Sciences, Royal College of Surgeons in Ireland, 123 Stephen's Green, Dublin 2, Ireland.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Bennett
authors.affiliation: HRB Centre for Primary Care Research, Royal College of Surgeons in Ireland, 123 Stephen's Green, Dublin 2, Ireland.
authors.forename: Tom
authors.initials: T
authors.lastname: Fahey
mesh_terms: D000328:Adult; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007494:Ireland; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008691:Methadone / Q000627:therapeutic use*; D008875:Middle Aged; D058850:Opiate Substitution Treatment / Q000706:statistics & numerical data*; D009293:Opioid-Related Disorders / Q000453:epidemiology* / Q000534:rehabilitation*; D010352:Patient Dropouts / Q000523:psychology* / Q000706:statistics & numerical data*; D011320:Primary Health Care / Q000706:statistics & numerical data*; D012307:Risk Factors; D013223:Statistics as Topic
chemical_list: D008691:Methadone
keywords: Methadone maintenance treatment; Proportional hazards models; Supervised consumption; Treatment retention