Schedule I controlled substance

A drug or other substance that has a high chance of being abused or causing addiction and has no FDA-approved medical use in the United States. Schedule I controlled substances are tightly regulated by the federal government. Examples of Schedule I drugs are heroin, LSD, and ecstasy. Although marijuana (Cannabis) is classified as a Schedule I controlled substance by the federal government, some states have passed laws that allow the medical and recreational use of marijuana. Also called Schedule I drug.