Understanding the Complex Challenges of Opioid Use Disorder Opioid use disorder, previously known as opioid addiction or opioid dependency, is a serious medical illness caused by regular use of prescription opioids, heroin, or other opiates. Opiates are found naturally in opium derived from the poppy plant and synthetic opioids created in labs. Commonly misused prescription opioids include oxycodone, hydrocodone, codeine, morphine, and fentanyl. Opioid...