In the 1960s, Dr. Marie Nyswander, a trained Freudian psychoanalyst, and Dr. Vincent Dole, a metabolic disease specialist who was chair of the NYC Health Research Council's Committee on Narcotics (not a job he particularly wanted) established the first methadone maintenance clinics in NY for heroin addicts. In the late fifties, Nyswander had begun working with jazz musicians addicted to heroin. The prevailing Freudian theory of heroin addiction at that time hypothesized that these male artists were actually homosexuals who used heroin to over-activate the superego and suppress the id. The overall understanding of drug addiction in the 60s was that there was an "addictive personality" type that took drugs to escape reality in order to conceal inadequacies. Frustrated by her experience with her patients' propensity to relapse, Nyswander accepted a position at the
More info about methadone: it is a long-lasting mu opioid receptor agonist. It reduces craving and withdrawal symptoms, but does not produce euphoria unless doses are very high. If heroin is administered while methadone is on board, it prevents the euphoria associated with heroin. Its use as a replacement therapy is controversial and affected by general attitudes and perceptions about drug addiction. The late 70s especially saw strong demand to not open more methadone clinics, as punitive measures against drug addicts again became popular. Its controlled substance status prevents it from being administered by a personal physician, and it can only be given at one of these special clinics (it also is rarely allowed to be self-administered at home). I believe the Drug Enforcement Agency, and not a health care organization, is still the group that operates methadone clinics.
More about heroin: Heroin is converted into morphine in the brain, and acts at μ-opioid receptors on GABA inhibitory interneurons in the ventral tegmental area. This activation may close N-type calcium channels, possibly through G-protein interactions or inhibition of adenylyl cyclase. These interneurons are therefore inhibited. The resulting disinhibition at the post-synaptic cell leads to increased firing of dopaminergic cells that are usually inhibited by these interneurons.
The first epidemic of opiate addiction in the