The association between cocaine use and short-term outcomes for the treatment of heroin dependence: findings from the Australian Treatment Outcome Study (ATOS).

The aim of this study was to determine the prevalence of cocaine use among individuals presenting for treatment for heroin dependence, describe the clinical profile of heroin users who also use cocaine and to establish the effects of cocaine use on short term outcomes for the treatment for heroin dependence. A longitudinal follow-up of 549 heroin users recruited in Sydney for the Australian Treatment Outcome Study was conducted at 3-month post-baseline interview. At baseline, current cocaine use was common (39%) and was associated with increased drug use, needle risk taking and criminality. The 3-month prevalence of cocaine use declined significantly to 19%. Thirty-five per cent of those who had used cocaine at baseline continued to use at 3 months, while 9% of the sample had commenced cocaine use. Those who entered residential rehabilitation at baseline were less likely than other treatment entrants and the non-treatment group to have used cocaine at follow-up. Treatment retention was not affected by baseline cocaine use status; however, baseline cocaine users (CU) displayed higher levels of heroin use, polydrug use and drug-related problems. A poorer outcome was associated with the commencement or continuation of cocaine use, while cessation of cocaine use resulted in significant improvements on these measures. Cocaine use was common among individuals seeking treatment for heroin dependence and was an important moderator of treatment outcome. It appears that cocaine use has a strong negative effect on treatment outcome over and above that caused by polydrug use generally.