Schedule I substances are characterized by which of the following?

Schedule I substances are indeed characterized by having no generally accepted medical uses. This classification indicates that these substances are considered to have a high potential for abuse and lack accepted safety for use even under medical supervision. As a result, they are heavily regulated and are only permissible for research purposes with strict controls.

Drugs classified in Schedule I, such as heroin or lysergic acid diethylamide (LSD), are not recognized for therapeutic applications within the medical community due to their potential for severe psychological or physical dependence. This classification serves to prevent misuse and protect public health.