Which of the following describes a scheduled drug?

A scheduled drug is primarily defined by its potential for abuse and the accompanying regulations that govern its use. Drugs that fall into this category tend to have a significant risk of addiction or dependency. The classification of these drugs is typically part of a controlled substances schedule, which ranks them based on their medical utility and abuse potential.

The correct choice emphasizes that a drug with a high potential for abuse is inherently dangerous and is therefore monitored closely by regulatory authorities. This classification serves to prevent misuse and protect public health while allowing for the necessary medical use under strict guidelines.

The other choices describe characteristics that do not inherently indicate a controlled status. A drug with established medical use may not be scheduled if it does not have a high potential for abuse. Similarly, over-the-counter drugs are generally not subject to scheduling because they have lesser risks associated with abuse. Lastly, the safety of a drug for pets does not relate to its abuse potential and does not influence its status as a scheduled substance. Thus, the focus on abuse potential makes the correct answer particularly relevant in understanding the nature of scheduled drugs.