Which of these drugs is not part of Schedule IV?

Oxycodone is classified as a Schedule II controlled substance under the Controlled Substances Act. This classification reflects its higher potential for abuse compared to drugs in Schedule IV. Schedule II substances have stricter regulations and are associated with a high risk of physical or psychological dependence, warranting careful control and monitoring.

In contrast, the other drugs listed belong to Schedule IV, which is reserved for substances that have a lower potential for abuse relative to those in the higher schedules. Schedule IV drugs are often prescribed for medical purposes with less regulatory scrutiny compared to Schedule II drugs, making it clear why the classification of Oxycodone as a Schedule II substance differs from the others in the question.