Aims: To determine the effects of cocaine use across the study period on outcomes of treatment for heroin dependence 12 months post-treatment entry.
Design: Longitudinal cohort (12 months). Interviews were conducted at baseline, 3 and 12 months.
Setting: Sydney, Australia.
Participants: Four hundred ninety-five heroin users recruited for the Australian Treatment Outcome Study and re-interviewed at 12-month follow-up.
Findings: Cocaine was widely used among treatment entrants in NSW, with almost all having a lifetime history of cocaine use and almost half having used in the month preceding baseline. While there was an overall decline in cocaine use across the study period, individual use patterns varied widely. Approximately half of the cohort did not report cocaine use at any data point, with the remainder reporting having used at one (29%), two (12%), or at all three (5%) points. Cocaine use across the study period was an independent predictor of most major treatment outcomes, with more cocaine use points predicting poorer outcome. Persistent cocaine use predicted a higher prevalence of homelessness, heroin use, daily injecting, needle sharing and injection-related health problems at 12 months as well as more extensive recent polydrug use.
Conclusions: Cocaine use was common among individuals seeking treatment for primary heroin dependence in NSW. Any cocaine use over the study period was associated with poorer outcomes in virtually all areas. Persistent cocaine use over the study period, however, appeared particularly detrimental. Cocaine use among clients should evidently be a cause for concern amongst treatment providers and may warrant being specifically targeted during treatment.