Opioid addiction and opioid dependence, sometimes classified together as an opioid use disorder, are medical conditions that characterize the compulsive use of opioids (e.g., morphine, heroin, codeine, oxycodone, hydrocodone, etc.) in spite of consequences of continued use and the withdrawal syndrome that occurs when opioid use stops. The necessary descriptive characteristics of the medical diagnosis are preoccupation with a desire to obtain and take the drug and persistent drug-seeking behaviour. The opioid dependence-withdrawal syndrome involves both psychological dependence and marked physical dependence upon opioid compounds.