What defines a controlled substance?

A controlled substance is defined primarily as a substance that is regulated by law due to its potential for abuse and dependency. This includes drugs that are categorized in Schedules I through V of the Controlled Substances Act. The scheduling system ranks substances based on their medical use, potential for abuse, and safety or dependence risk.

Substances classified under these schedules range from highly addictive drugs with no accepted medical use (like heroin, categorized under Schedule I) to medications with lower potential for abuse (like certain medications in Schedules IV and V). This definition captures the essence of what makes a substance "controlled" and encompasses various drugs that might be used in clinical settings, as well as those that are subject to strict regulations due to their abuse potential.

The other options do not adequately define a controlled substance. For example, a substance used solely for recreational purposes does not necessarily imply regulation or control, as not all recreational substances are classified as controlled. Similarly, while drugs recognized in US official pharmacopoeias may overlap with controlled substances, not all drugs listed there are controlled. Lastly, a combination of non-narcotic medications does not encompass the wide range of substances that can be classified as controlled, as many controlled substances are indeed narcotic or have potential for abuse