Understanding Substance Use Disorder (SUD) Substance Use Disorder, often referred to as SUD, is a medical condition marked by the uncontrollable use of substances, including alcohol and drugs, despite negative consequences. The prevalence of SUD has risen alarmingly, making it imperative to address not just due to the serious health implications, but also because it often stands between life and death. Substances commonly abused encompass a range from alcohol, prescription medications to illicit drugs. Among these, fentanyl, a potent synthetic opioid, has been a significant concern due to its lethal potential.