Which substance is used to treat severe pain and is classified under Schedule II?

Hydromorphone is classified as a Schedule II controlled substance specifically because it is considered to have a high potential for abuse, which may lead to severe psychological or physical dependence. This classification is critical for substances that are effective in treating severe pain but also pose a significant risk if not used properly.

Hydromorphone is a potent opioid analgesic, often utilized for managing acute or chronic pain in patients who require strong pain relief. Its effectiveness in pain management, combined with its controlled status, reflects the balance between therapeutic need and the risks associated with opioid medications.

The other substances listed have different classifications and uses. Codeine, while it is an opioid, is generally classified as a Schedule III or V substance depending on its formulation and dosage, which indicates a lower potential for abuse compared to hydromorphone. Alprazolam, used mainly for anxiety and panic disorders, is classified as a Schedule IV substance, reflecting a lower risk. Marinol, containing synthetic THC, is classified under Schedule III because it has less potential for abuse than the Schedule II opioids. Thus, hydromorphone stands out as the only true Schedule II medication specifically indicated for the treatment of severe pain.