Which of the following drugs is NOT classified as Schedule I?

Methylphenidate is classified as a Schedule II controlled substance rather than a Schedule I drug. Schedule II drugs are those that have a high potential for abuse and have accepted medical uses in treatment, albeit with severe restrictions. Methylphenidate, commonly used to treat attention deficit hyperactivity disorder (ADHD) and narcolepsy, falls into this category due to its therapeutic applications and well-defined medical use.

In contrast, drugs classified as Schedule I, such as heroin, LSD, and mescaline, are considered to have a high potential for abuse and do not have any accepted medical use in the United States. These substances are heavily regulated and not available for medical treatment, underscoring their status in terms of both legal restriction and public health risk. Thus, the classification of methylphenidate as Schedule II illustrates its recognized medical value, setting it apart from the drugs that are classified as Schedule I.