Which of the following is an example of a Schedule I drug?

Heroin is classified as a Schedule I drug under the Controlled Substances Act. This classification is reserved for substances that have a high potential for abuse, have no currently accepted medical use in treatment in the United States, and lack accepted safety for use under medical supervision. Heroin fits all of these criteria, as it is known for its addictive properties and is used illicitly without any recognized medical use.

In contrast, the other substances listed have recognized medical applications. Codeine and morphine are both used in medical contexts for pain management and are classified as Schedule II drugs, which still have a high potential for abuse but are accepted for medical use. Vicodin, which is a combination of hydrocodone and acetaminophen, is also a Schedule II drug, indicating it can be prescribed for pain relief while still being regulated due to potential for addiction. Understanding these classifications helps to emphasize the treatment context and legal restrictions associated with each substance.