Which of the following drugs is used worldwide for the maintenance therapy of opioid dependence?

Ans. (B) Methadone(Ref: Katzung 11/e p560; KDT 8/e p 504)Methadone is a synthetic narcotic (an opioid) that substitutes for heroin and can be taken orally. When given to addicts to replace their usual substance of abuse, the drug suppresses withdrawal symptoms. The duration of action for methadone exceeds 24 hours; thus, once-daily dosing is adequate. Methadone maintenance has several advantages.It frees persons with opioid dependence from using injectable heroin and, thus, reduces the chance of spreading HIV through contaminated needles.Methadone produces minimal euphoria and rarely causes drowsiness or depression when taken for a long time.Methadone allows patients to engage in gainful employment instead of criminal activity.