Substitution is defined as the administration under medical supervision of a prescribed psychoactive substance, pharmacologically related to the one producing dependence, to people with substance dependence, for achieving defined treatment aims.
OST is a form of health care for heroin and other opiate-dependent people using prescribed opioid agonists, which have similar or identical properties to heroin and morphine on the brain and which alleviate withdrawal symptoms and block the craving for illicit opiates.
The aims of substitution treatment are:
To assist people in remaining healthy until, with the appropriate care and support, they can achieve a drug-free life or, if they cannot or want to quit the program, be in treatment for years or even for their lifetime;
To reduce the use of illicit or non-prescribed drugs;
To deal with problems related to drug misuse;
To reduce the dangers associated with drug misuse, particularly the risk of transmitting HIV, hepatitis B and C virus and other blood-borne infections from injecting and sharing injecting kits;
To reduce the duration of episodes of drug misuse;
To reduce the chances of future relapse to drug misuse;
To stabilize the person where appropriate on a substitute medication to alleviate withdrawal symptoms;
To improve overall personal, social and family functioning.