Which of the following is NOT a Schedule IV controlled substance?

Ketamine is classified as a Schedule III controlled substance rather than a Schedule IV. Schedule IV substances are typically characterized by their lower potential for abuse relative to those in higher schedules and are often associated with medications that have accepted medical uses, such as anxiety or sleep disorders. Alprazolam, phentermine, and chlordiazepoxide are all recognized as Schedule IV due to their potential for abuse and dependence, but they also possess therapeutic benefits in managing certain conditions.

Alprazolam is commonly used for anxiety and panic disorders, phentermine is used as an appetite suppressant, and chlordiazepoxide is effective for anxiety and alcohol withdrawal management. In contrast, ketamine has a different profile; it is utilized mainly for anesthesia and certain psychiatric conditions and is recognized for its potential for abuse, placing it in Schedule III. This distinction highlights the importance of understanding the scheduling criteria and therapeutic context of various controlled substances in pharmacy practice.