title: Genetic influence on methadone treatment outcomes in patients undergoing methadone maintenance treatment for opioid addiction: a pilot study.
abstract: BACKGROUND
  Treatment of opioid addiction with methadone is effective; however, it is known to produce interindividual variability. This may be influenced in part by genetic variants, which can increase the initial risk of developing opioid addiction as well as explain differences in response to treatment. This pilot study aimed to assess the feasibility of conducting a full-scale genetic analysis to identify genes that predict methadone treatment outcomes in this population.
  
  
  METHODS
  This was a cross-sectional observational study of patients admitted to a methadone maintenance treatment program for opioid addiction. We obtained demographic and clinical characteristics in addition to blood and urine samples, for the assessment of treatment outcomes.
  
  
  RESULTS
  The recruitment process yielded 252 patients, representing a 20% recruitment rate. We conducted genetic testing based on a 99.6% rate of provision of DNA samples. The average retention in treatment was 3.4 years, and >50% of the participants reported psychiatric and medical comorbidities. BDNF rs6265 and DRD2 rs1799978 were the common single nucleotide polymorphisms (SNPs) selected for the feasibility study.
  
  
  CONCLUSIONS
  This study met our predetermined feasibility criteria; recruitment, response rates, and genetic testing were feasible; treatment duration was sufficient for follow up; and the prevalence of comorbid conditions indicated the need for reliable psychiatric and chronic pain measures. The study strengths included effective collaboration with clinics and the generalizability of sample population. Key learning points show the need for assessment of treatment outcomes on multiple domains, implementation of follow up, and the development of standardized training for the study clinical staff.
authors.affiliation: Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada ; Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada ; Population Genomics Program, Chanchlani Research Centre, McMaster University, Hamilton, Ontario, Canada ; MiNDS Neuroscience Program, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Zainab
authors.initials: Z
authors.lastname: Samaan
authors.affiliation: Population Genomics Program, Chanchlani Research Centre, McMaster University, Hamilton, Ontario, Canada ; MiNDS Neuroscience Program, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Monica
authors.initials: M
authors.lastname: Bawor
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada ; Population Genomics Program, Chanchlani Research Centre, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Brittany B
authors.initials: BB
authors.lastname: Dennis
authors.affiliation: Ontario Addiction Treatment Centres, Richmond Hill, Ontario, Canada.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Plater
authors.affiliation: Ontario Addiction Treatment Centres, Richmond Hill, Ontario, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Varenbut
authors.affiliation: Ontario Addiction Treatment Centres, Richmond Hill, Ontario, Canada.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Daiter
authors.affiliation: Ontario Addiction Treatment Centres, Richmond Hill, Ontario, Canada ; Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Worster
authors.affiliation: Ontario Addiction Treatment Centres, Richmond Hill, Ontario, Canada ; Northern Ontario School of Medicine, Laurentian University, Sudbury, Ontario, Canada.
authors.forename: David C
authors.initials: DC
authors.lastname: Marsh
authors.affiliation: Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Charlie
authors.initials: C
authors.lastname: Tan
authors.affiliation: Population Genomics Program, Chanchlani Research Centre, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Dipika
authors.initials: D
authors.lastname: Desai
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada ; Biostatistics Unit, Centre for Evaluation of Medicine, McMaster University, Hamilton, Ontario, Canada ; System Linked Research Unit, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Lehana
authors.initials: L
authors.lastname: Thabane
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Pare
keywords: genetics; risk factors; substitute opioid therapy; treatment response