"Although a drug-free state represents an optimal treatment goal, research has demonstrated that this goal cannot be achieved or sustained by the majority of opiate-dependent people. However, other laudable treatment goals, including decreased drug use, reduced criminal activity, and gainful employment can be achieved by most MMT [methadone maintenance treatment] patients."

Source

National Institutes of Health, Office of the Director, "NIH Consensus Statement: Effective Medical Treatment of Opiate Addiction," (U.S. Department of Health: Bethesda, MD, November 1997) Vol. 15, No. 6., p. 4.
http://consensus.nih.gov/1997…