It is a synthetic heroin substitute and has comparable analgesic properties of heroin.
Its available in oral, subcutaneous, intramuscular and rectal forms.
In replacement therapies for heroin addiction.
Methadone in many ways is quantitatively similar to that of morphine. Causes a withdrawl similar to that of morphine, but wit a slower start, more prolonged course and witth less severe symtoms.
Unlike morphine and herion it can be administered orally (avoiding introvenous use), has a slow elimination , 25-30 hours, and this allows for a single daily administration, while other opiates require repeated daily intakes.
Oral administration increases the duration of analgesia; is rapidly absorbed and has significant concentrations in the blood, by 3-4 hours of intake. The plasma activity of methadone is 25-30 hours; the necessary brain concentrations are reached after only 1-2 hours of administration
Sedation, change in mood (euphoria, quiet, etc), miosis (constriction of pupils), changes in sensory and functional abilities (ie, effects on decision making skills, perception disorders, etc). Methadone may also have an adverse effect on the speed and direction of an individual
In the short term it can cause respiratory depression central dose-dependent, nausea, vomiting, headache and confusion. In longer periods it can cause problem with sleep and concentration. There is also the risk of the development of tolerance, physical dependance and a “heavy” psychological withdrawl syndrome.