Participants of this study are 120 heroin-addicted patients who are inward for a detoxification program for either cocaine or cocaine and heroin. Depending on the detoxification substance(s) there will be two groups of participants: Detoxification of cocaine (A; 60 participants) and detoxification of heroin and cocaine (B; 60 participants). The detoxification starts mandatory with the admission to the ward and lasts about 1-2 weeks. The participation in the study lasts about 4-5 weeks (including follow-up visits). Intake of study medication starts two days after admission and one day after informed consent. Each participant will get either 30mg/d prednisolon or placebo during five days. Participants will be under normal medical supervision during the treatment phase until follow-up 2 (final examination) provided by ward staff. Treatment days and follow-up 1 and 2 consist of : (1) vital signs (BP, HR, temperature) as measured in the daily routine, (2) at midday: visual analogue scales asking about craving for heroin and cocaine at the moment, (3) afternoon: questionnaires to survey mainly the withdrawal symptoms and vegetative parameters.