The Drug Enforcement Agency (DEA), an arm of the United States Justice Department, classifies controlled substances according to five schedules, based on whether they have a currently accepted medical use in treatment in the United States, the potential for abuse and dependence liability (physical and psychological) of the medication, and likelihood of causing dependence when abused. Some states may have stricter prescription regulations. Physicians, dentists, podiatrists, and veterinarians may prescribe controlled substances. Nurse practitioners and physician assistants may also prescribe controlled substances with limitations that vary from state to state.

Potential for abuse is so high as to be unacceptable. Have no currently accepted medical use in the United States. May be used for research with appropriate limitations. Examples are marijuana, LSD, and heroin.

High potential for abuse which may lead to severe physical and psychological dependence (amphetamines, opioid analgesics, certain barbiturates). Outpatient prescriptions must be in writing. In emergencies, telephone orders may be acceptable if a written prescription is provided within 72 hr. No refills are allowed.

Substances in this schedule have a potential for abuse less than substances in Schedules I or II, and abuse may lead to moderate or low physical dependence or high psychological dependence (certain nonbarbiturate sedatives, certain nonamphetamine CNS stimulants, and certain opioid analgesics). Outpatient prescriptions can be refilled 5 times within 6 mo from date of issue if authorized by prescriber. Telephone orders are acceptable.

Less abuse potential than Schedule III with minimal liability for physical or psychological dependence (certain sedatives/hypnotics, certain antianxiety agents, certain nonamphetamine CNS stimulants, some barbiturates, and benzodiazepines). Outpatient prescriptions can be refilled 6 times within 6 mo from date of issue if authorized by prescriber. Telephone orders are acceptable.

Minimal abuse potential. Number of outpatient refills determined by prescriber. Some products (cough suppressants with small amounts of codeine, antidiarrheals containing paregoric, pregabalin) may be available without prescription to patients >18 yr of age.