Which of the following is NOT included in the definition of a controlled substance?

Hemp is not included in the definition of a controlled substance because it is classified separately due to its low THC content as per the 2018 Farm Bill. This legislation legalized hemp at the federal level, distinguishing it from marijuana, which is often classified as a controlled substance due to its psychoactive properties.

In contrast, the other options—chemical analogues, counterfeit substances, and adulterants—are explicitly included in the definitions surrounding controlled substances. Chemical analogues are substances that are chemically similar to known controlled substances and can produce similar effects. Counterfeit substances involve drugs that are misrepresented in terms of their composition or appearance. Adulterants refer to substances that may alter the effectiveness or the composition of controlled substances. Therefore, all these categories relate to the regulation and enforcement of controlled substances, while hemp is treated distinctly in regulatory frameworks.