Which of the following best defines “controlled substances”?

The definition of "controlled substances" refers specifically to drugs that are regulated by law due to their potential for abuse and dependence. This classification is designed to minimize risks associated with misuse while ensuring availability for legitimate medical use. Controlled substances typically have specific restrictions on their manufacture, distribution, prescribing, and dispensing.

Option B accurately captures this definition, as it highlights the key concerns of potential for abuse and the regulatory measures that accompany such substances. Under federal law, controlled substances are categorized into schedules (I through V) based on their potential for abuse, accepted medical use, and safety or dependence liability. These laws ensure that while such substances may be used therapeutically, they are closely monitored to prevent misuse.

In contrast, the other options do not convey the appropriate regulatory context associated with controlled substances. For instance, drugs available without a prescription, vitamins, dietary supplements, and over-the-counter items typically do not fall under the same stringent regulations as controlled substances. Therefore, option B stands out as the most accurate representation of controlled substances within the framework of drug regulation.