Final answer:
Sam is most likely abusing a Schedule II drug, which has recognized medical uses but a high potential for abuse and severe dependence.
Step-by-step explanation:
Based on the description of the drug that Sam is abusing, it matches the characteristics of a Schedule II substance under the Federal Controlled Substances Act. Schedule II drugs have a high potential for abuse and may lead to severe psychological or physical dependence, but they also have some currently accepted medical uses. Examples of such substances include certain opioids, stimulants, and central nervous system (CNS) depressants that can be associated with addiction or compulsion in misuse scenarios.