Apart from the termination of the heroin treatment at the end of the experimental period for all subjects in the treatment groups B and C, and upon completion of phase III for subjects in group A, the treatment with co-prescribed heroin could be - temporarily or permanently - terminated on an individual basis by the treating physician if a subject clearly evidenced negative effects from the prescription of heroin. In addition, the treatment with heroin was terminated if a patient clearly expressed the wish to stop the treatment with heroin, or if the patient was not able to attend the treatment site anymore (for example, because he had moved to another city, or because he became imprisoned). In female participants, the heroin treatment was terminated in case of pregnancy, confirmed by a positive pregnancy test, in which case the patient was referred to a general practitioner or gynecologist for further prenatal care. Lastly, the heroin treatment was - temporarily or permanently - stopped if a patient was suspended from the treatment program, for example because he had exhibited aggressive behavior or had repeatedly attempted to steal or smuggle heroin out of the treatment unit.