Which of these substances is generally not prescribed due to its high potential for abuse and is classified as Schedule II?

Secobarbital is classified as a Schedule II controlled substance due to its high potential for abuse and the risk of severe psychological or physical dependence it poses. Schedule II substances are tightly regulated under the Controlled Substances Act because they can lead to significant harm if misused. This classification indicates that while secobarbital has legitimate medical uses, such as for short-term treatment of insomnia or as a sedative, the potential for abuse is high, making it less frequently prescribed compared to substances with lower abuse potential.

In contrast, tramadol is classified as a Schedule IV substance due to its lower potential for dependence compared to Schedule II drugs. Diphenhydramine, commonly used as an antihistamine, is not a controlled substance at all, and quetiapine, an atypical antipsychotic, is also not classified as a controlled substance, making them less restricted. Thus, secobarbital stands out as the substance that is both classified as Schedule II and recognized for its high potential for abuse, leading to its limited prescribing in practice.