Which of the following is a Schedule II controlled substance?

Pentobarbital is classified as a Schedule II controlled substance under the Controlled Substances Act. This classification is based on its high potential for abuse, which can lead to severe psychological or physical dependence. Schedule II substances are strictly regulated, requiring a written prescription from a licensed healthcare provider, and cannot be refilled. Common uses for pentobarbital include its application as a hypnotic agent or in the treatment of seizures, but due to its potential for misuse and serious side effects, it is closely monitored.

The other substances listed fall into different scheduling categories. Alprazolam and diazepam, for instance, are classified as Schedule IV controlled substances, indicating a lower potential for abuse and dependence compared to Schedule II substances. Diphenhydramine is considered an over-the-counter medication and is not classified as a controlled substance at all. Understanding these classifications is essential for anyone involved in the dispensing or administration of medications to ensure compliance with federal regulations.