BACKGROUND: A recent switch in methadone formulation from methadone (1 mg/mL) to Methadose (10 mg/mL) in British Columbia (BC), Canada, was associated with increased reports of opioid withdrawal and increases in illicit opioid use. Impacts on other forms of drug use have not been assessed. Since alcohol use is common among people receiving Medication-Assisted Treatment (MAT), we assessed if switch was associated with increased prevalence of heavy alcohol use.

METHODS: Drawing on data from two open prospective cohort studies of people who inject drugs in Vancouver, BC, generalized estimating equations (GEE) model examined relationship between methadone formulation change and heavy alcohol use, defined by National Institute for Alcohol Abuse and Alcoholism (NIAAA). A sub-analysis examined relationship with heavier drinking defined as at least eight drinks per day on average in last six months.

RESULTS: Between June 2013 and May 2015, a total of 787 participants on methadone were eligible for the present analysis, of which 123 (15.6%) reported heavy drinking at least once in last six months. In an unadjusted GEE model, Methadose use was not significantly associated with an increased likelihood of heavy drinking [Odds Ratio (OR) = 1.03; 95% Confidence interval (CI) = 0.87-1.21]. Methadose use was not significantly associated with an increased likelihood of drinking at least eight drinks daily on average (OR = 1.09, 95% CI = 0.72-1.65).

CONCLUSIONS: Despite reported changes in opioid use patterns coinciding with the change, there appeared to be no effect of the methadone formulation change on heavy drinking in this setting.