Fewer days of cocaine use ( p = 0.074 ) , fewer days engaged in illegal activities at baseline ( p < 0.01 ) and at each visit ( p < 0.01 ) , less money spent on drugs ( p < 0.001 ) , days with injection opioid or oral methadone treatment ( p < 0.001 ) and total mg of injectable opioids taken ( p < 0.001 ) , independently predicted lower use of illicit heroin .