Which of the following drugs is categorized as a Schedule IV (C4) substance?

Tramadol is classified as a Schedule IV (C4) substance primarily due to its potential for abuse and the therapeutic benefits it provides. Schedule IV substances are defined as drugs that have a lower potential for abuse relative to drugs in higher schedules, but do still have some risk for dependency or addiction. Tramadol is often used for pain relief and has a mechanism that can produce effects similar to opioids, but it is deemed to have a lower abuse potential than Schedule II or III medications.

In contrast, Ketamine is classified as a Schedule III substance due to its strong anesthetic properties and potential for abuse as a hallucinogen. Marijuana, while legal in several states for medicinal or recreational use, is considered a Schedule I substance at the federal level, indicating a high potential for abuse and having no accepted medical use. Meperidine, an opioid analgesic, is classified as a Schedule II substance because of its higher potential for abuse and addiction. Thus, Tramadol is appropriately categorized as a Schedule IV substance within this context.