What defines a controlled substance analog?

A controlled substance analog is defined by its similar chemical structure to a controlled substance. This means that the analog is not only chemically related to the controlled substance but may also exhibit similar effects or characteristics. The law recognizes controlled substance analogs as substances that can be considered illegal or regulated if they possess such structural similarities because they may mimic the effects of their controlled counterparts.

The other options do not accurately capture the legal definition of a controlled substance analog. For instance, a substance that has no known effects does not necessarily relate to its definition; it could potentially still be classified as an analog if it has a similar structure. Similarly, a substance that is limited to medicinal use does not inherently define an analog, as many controlled substances are used for medical purposes as well. Lastly, stating that a substance is illegal in all cases does not align with the definition either; the legality often depends on the specific structure and effects of the substance in relation to existing controlled substances. Thus, the essence of a controlled substance analog is its chemical similarity to a controlled substance, which may result in similar effects.