Which of the following is classified as a Schedule 1 drug?

Heroin is classified as a Schedule I drug because it has a high potential for abuse and no accepted medical use in treatment in the United States. Schedule I drugs are considered to have the highest level of restriction due to the risks associated with their use. The categorization reflects significant concerns about physical and psychological dependence, as well as the lack of accepted safety for use under medical supervision.

In contrast, the other substances mentioned have established medical uses and are thus classified differently. Oxycodone, for example, is a potent opioid pain medication and is classified as a Schedule II drug, indicating it has a recognized medical application but also a high potential for abuse. Similarly, Ambien (used to treat insomnia) and Ativan (an anti-anxiety medication) are classified as Schedule IV drugs, signifying a lower potential for abuse compared to Schedule I and II substances, while still being monitored due to the potential for dependency and misuse.