The Controlled Substances Act of 1970 regulates the production and distribution of stimulants, narcotics, depressants, hallucinogens, and anabolic steroids. Drugs regulated by this law fall into five categories, or schedules, based on their abuse potential, medicinal value, and harmfulness. Schedule I drugs are the most hazardous; schedule V drugs, the least hazardous.

Schedule I: High potential for abuse; no currently accepted medical use in the United States. Using the drug even under medical supervision is thought to be unsafe.

Schedule II: High potential for abuse; currently accepted medical use in the United States (or currently accepted medical use with severe restrictions). Abuse may lead to severe psychological or physical dependence. Emergency telephone orders for limited quantities may be authorized, but the prescriber must provide a written, signed prescription order.

Schedule III: Lower abuse potential than schedule I and II drugs; currently accepted medical use in the United States. Abuse may lead to a moderate or low degree of physical dependence or high psychological dependence. Telephone orders are permitted.

Schedule IV: Lower abuse potential than schedule I, II, or III drugs; currently accepted medical use in the United States. Abuse may lead to limited physical dependence or psychological dependence. Telephone orders are permitted.

Schedule V: Low abuse potential compared to drugs in other schedules; currently accepted medical use in the United States. Abuse may lead to limited physical dependence or to psychological dependence. Some schedule V drugs may be available in limited quantities without a prescription (if permitted under state law).