Effect of cocaine use on methadone pharmacokinetics in humans.

Chronic cocaine use has been shown to significantly decrease buprenorphine concentrations in the blood with potential for adverse events and poor treatment response. In this study, we investigated whether a similar drug interaction occurred between cocaine and methadone. In a retrospective analysis, methadone pharmacokinetics were compared for those who were either regular cocaine users (N = 16) or with intermittent or no cocaine use (N = 23). Participants who used cocaine regularly showed a significant decrease in C(min) (p = .04) and a trend for decreased AUC (p = .09) and more rapid methadone clearance (p = .08). Regular cocaine use may adversely impact treatment outcomes for opioid dependence in those receiving methadone maintenance by decreasing methadone exposure.