What is an example of a Schedule I controlled substance?

Heroin is classified as a Schedule I controlled substance due to its high potential for abuse, lack of accepted medical use in the United States, and safety concerns. Schedule I substances are characterized by their potential for addiction and are considered to have no accepted therapeutic uses, making them illegal to manufacture, distribute, or possess.

In contrast, morphine, Adderall, and codeine are classified under different schedules because they have recognized medical uses and lower potential for abuse in comparison to Schedule I substances. Morphine is a Schedule II substance, indicating it has a high potential for abuse but also has accepted medical applications. Adderall, containing amphetamine salts, is classified as a Schedule II drug due to its medical use in treating ADHD but also its potential for abuse. Codeine is generally considered a Schedule II or III controlled substance, depending on its formulation and concentration.

Thus, heroin distinctly fits the criteria for a Schedule I substance, making it the correct answer.