Which of the following best describes the difference between schedule I and schedule II controlled substances in Colorado?

The distinction between schedule I and schedule II controlled substances is primarily centered around their accepted medical uses and legal status in medical practice. Schedule I substances are classified as having a high potential for abuse and no accepted medical use in the United States. This means they cannot be prescribed or dispensed by medical professionals, making them entirely unavailable for prescription. Examples include substances like heroin and LSD.

On the other hand, schedule II substances are recognized as having legitimate medical uses, albeit with a high potential for abuse that may lead to severe psychological or physical dependence. Medications in this category can be prescribed legally, but they are subject to strict regulations regarding their prescribing and dispensing.

Thus, the assertion that schedule I substances are not available by prescription accurately captures this fundamental difference, while schedule II substances are indeed available for medical use under regulated circumstances.