Commonly referred to as prescription opioids, medications that have been used to treat moderate to severe pain in some patients.

A problematic pattern of opioid use that causes significant impairment or distress. A diagnosis is based on specific criteria such as unsuccessful efforts to cut down or control use, or use resulting in social problems and a failure to fulfill obligations at work, school, or home, among other criteria. Opioid use disorder is preferred over other terms with similar definitions, “opioid abuse or dependence” or “opioid addiction.”

Injury to the body (poisoning) that happens when a drug is taken in excessive amounts. An overdose can be fatal or nonfatal.

Originally referred to any substance that dulled the senses and relieved pain. Some people use the term to refer to all illegal drugs but technically, it refers only to opioids. Opioid is now the preferred term to avoid confusion.