Name a common Schedule I drug under the PRPA classification.

Heroin is classified as a Schedule I drug under the PRPA, which indicates that it has a high potential for abuse, no accepted medical use in treatment in the United States, and a lack of accepted safety for use under medical supervision. Schedule I drugs are considered the most restricted category and are known for their severe legal controls due to their significant risks associated with addiction and overdose.

In the context of the other substances listed, cocaine is classified as a Schedule II drug, meaning it has a recognized medical use but still carries the potential for significant abuse. Marijuana's classification varies by jurisdiction, but it is often not categorized as a Schedule I drug in many states due to evolving laws recognizing its medical applications. MDMA is also categorized under Schedule I substances, but heroin is perhaps more historically recognized and significant in the context of narcotics and dangerous drugs.