Methods: Thirty heroin-dependent patients on stable heroin maintenance will be examined in a randomized placebo-controlled crossover design. They will be compared with 30 heroin-dependent age- and gender-matched but otherwise healthy volunteers receiving saline. The heroin-dependent patients will administer either their individual dose of prescribed DAM dose or saline through an indwelling intravenous line. Afterwards they will complete four experimental paradigms testing response inhibition, emotional processing and working memory while brain responses are measured with fMRI. Before and after the fMRI investigation cortisol samples, DAM blood levels, neurophysiological and psychological stress parameters, such as skin conductance, heart rate, anxiety, anger, and heroin craving will be measured.