Addiction medicine is practiced by a diverse group of physicians from different treatment settings: clinics providing methadone or other opiate replacement therapy to heroin addicts, chemical dependency treatment hospitals, publicly funded drug abuse treatment clinics, and private practice. The various groups of addiction medicine specialists evolved independent of one another and of mainstream medicine.
Regulations and funding mechanisms for drug abuse treatment fostered separation from mainstream medicine. Public funding of drug abuse treatment, especially opioid maintenance therapy, is not part of the national health care budget. Most public-sector drug abuse treatment is funded through block grants to states from the Center for Substance Abuse Treatment, part of the federal government's war on drugs. Physicians are legally prohibited from prescribing opioid substitution medications for heroin addicts, except in specially licensed clinics. The methadone maintenance treatment system, which evolved outside mainstream medicine, is still tightly regulated by the Food and Drug Administration