 Methadone maintenance has been shown to reduce the transmission of blood borne viruses associated with opioid injection, such as hepatitis B and C, and/or HIV.The principal goals of methadone maintenance are to relieve opioid cravings, suppress the abstinence syndrome, and block the euphoric effects associated with opioids.Chronic methadone dosing will eventually lead to neuroadaptation, characterised by a syndrome of tolerance and withdrawal (dependence).