Examining Drug Classifications

There are many hundreds of medications, prescription drugs and illicit substances.1 In the United States, the Food and Drug Administration is the government agency responsible for the oversight of prescription and over-the-counter drugs, ensuring both the safety and efficacy of medications, biological products and medical devices to protect the public.2 The number of medications—as well as other controlled substances—with the potential for abuse or misuse is lengthy. It is the responsibility of the Drug Enforcement Administration (DEA) to enforce federal controlled substances laws and regulations surrounding the manufacture, importation, possession, and distribution of drugs and their precursor compounds.1,3

The U.S. uses a five-level system to categorize controlled substances based on whether they have an accepted medical use and on its potential for misuse.1,4 The abuse rate is what determines a drug’s placement in the schedule and have a higher level of regulatory control.1

Many drugs became popular as prescribed pharmaceutical medications and other medical applications because of their balance of effectiveness, potency, and potential side effects. Without drug classification systems that incorporate levels of acceptable risk, many of the most widely prescribed pharmaceutical medications may not be in use today.

Drug Classifications in the United States

The controlled substance list published by the Drug Enforcement Agency contains five different classifications of drugs. These classifications, referred to as schedules, range from illegal and more dangerous drugs to safer drugs that many people use on a daily basis to manage chronic health conditions and minor pain.

Schedule I

Schedule I substances have a high potential for misuse.4 These drugs are only available for research and have no approved medical use in the U.S.

Examples of Schedule I drugs include the following:

  • Heroin.
  • Lysergic acid diethylamide (LSD).
  • Marijuana (cannabis)
  • 3,4-methylenedioxymethamphetamine (ecstasy)
  • Methaqualone.
  • Peyote.

Although marijuana is legal in many states for either medical or recreational purposes—or both, it is still currently listed as a Schedule 1 drug and illegal at the federal level. This also means that marijuana and the many medicinal products made from THC— the mind-altering drug that causes the “high”—have not been approved by nor are they regulated by the FDA. This has led to confusion among consumers, patients, researchers, caregivers, and healthcare providers.5

Schedule II

Schedule II drugs also have a high potential for abuse, with use potentially leading to severe psychological or physical dependence.4 These drugs are available only by prescription, and refills generally can’t be authorized.1

The controlled substances on Schedule II include:

  • Cocaine.
  • Methamphetamine.
  • Dexedrine.
  • Adderall.
  • Ritalin.
  • Methadone.
  • Hydromorphone (Dilaudid).
  • Meperidine (Demerol).
  • Oxycodone (OxyContin).
  • Fentanyl.
  • Combination products with less than 15 milligrams of hydrocodone per dosage unit (Vicodin).

In addition to only being available with a prescription, Schedule II drugs require additional paperwork for ordering, storage, and transfer, and annual production quotas are set by the DEA with drug manufacturers.4

Schedule III

Schedule III drugs have a moderate to low potential for physical and psychological dependence.4

Drugs identified as Schedule III controlled substances include:4

  • Ketamine.
  • Anabolic steroids.
  • Testosterone.
  • Pharmaceutical medications containing less than 90 milligrams of codeine per dosage unit (e.g., Tylenol with codeine).

Under federal controlled substance law, up to five refills in a 6-month period may be authorized and may be ordered verbally—state laws may be more stringent.1

Schedule IV

Schedule IV substance have a low potential for abuse and low risk of dependence. Some examples of Schedule IV drugs include:4

  • Xanax.
  • Soma.
  • Darvon.
  • Darvocet.
  • Valium.
  • Ativan.
  • Talwin.
  • Ambien.
  • Tramadol.

Like the drugs in Schedule III, Schedule IV drugs also allow for up to five refills in a 6-month period and additional refills may be ordered verbally.1

Schedule V

Schedule V drugs have a lower potential for abuse than Schedule IV controlled substances. Schedule V drugs consist of preparations containing limited quantities of certain narcotics and are generally used to relieve diarrhea, cough, or pain.4

Some examples of Schedule V drugs are:4

  • Lomotil.
  • Motofen.
  • Lyrica.
  • Parepectolin.
  • Cough medicines with less than 200 milligrams of codeine or per 100 milliliters (Robitussin AC).

Reassessing Schedules

Federal controlled substance laws and regulations allow for the rescheduling and reassessment of drug schedules. The law accommodates temporary changes to the schedules in response to emerging situations, including the development of a new drug or reclassifying an existing drug.6

Scheduling has also been used as a mechanism to reduce diversion of prescription drugs. Hydrocodone combinations (e.g., Vicoden, etc.)—the most commonly prescribed and non-medically used opioids—were rescheduled Schedule III to II in 2014, leading to a 22% reduction in hydrocodone prescribing over the subsequent year.1


  1. Miller, S. C., Fiellin, D. A., Rosenthal, R. N., & Saitz, R. (2019). The ASAM Principles of Addiction Medicine, Sixth Edition. Philadelphia: Wolters Kluwer.
  2. U.S. Food and Drug Administration. (n.d.). What We Do.
  3. U.S. Drug Enforcement Agency. (2019). DEA Mission Statement.
  4. U.S. Drug Enforcement Agency. (2019). Drug Scheduling.
  5. Mead A. The legal status of cannabis (marijuana) and cannabidiol (CBD) under U.S. law. Epilepsy Behav. 2017;70(Pt B):288–291.
  6. U.S. Drug Enforcement Agency. (2017). Drugs of Abuse.
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