Opioid dependência is a transtorno of regulation of opioid uso arising from repeated or continuous uso of opioids. The characteristic feature is a strong internal drive to uso opioids, which is manifested by impaired ability to control uso, increasing priority given to uso over other activities and persistence of uso despite harm or negative consequences. These experiences are often accompanied by a subjective sensation of urge or craving to uso opioids. Physiological features of dependência may also be present, including tolerance to the effects of opioids, abstinência symptoms following cessation or reduction in uso of opioids, or repeated uso of opioids or pharmacologically similar substances to prevent or alleviate abstinência symptoms. The features of dependência are usually evident over a period of at least 12 months but the diagnosis may be made if opioid uso is continuous (daily or almost daily) for at least 3 months.