Drug Classifications: How Legal And Illegal Drugs Are Classified

Medically Reviewed by Johnelle Smith, M.D on April 19, 2021

All drugs, including prescription medications, are classified into one of five schedules, or categories. Drug classification can affect regulation, criminal penalties, and the perceived risk of drug misuse and addiction.

How Drugs Are Classified

In the United States, all legal and illegal drugs are classified by the federal government into five categories, under the Controlled Substances Act (CSA).

Federal drug classifications in the United States include:

  • Schedule I drugs
  • Schedule II drugs
  • Schedule III drugs
  • Schedule IV drugs
  • Schedule V drugs

The legal classification of a drug can affect its regulation, criminal penalties, and the potential of a drug to be misused or become addictive.

How Are Drugs Classified?

All drugs are classified by the U.S. Drug Enforcement Administration (DEA). This is a law enforcement agency under the U.S. Department of Justice.

Several factors are taken into consideration when classifying a drug. Classifications for drugs can change, if new information that is relevant to a drug’s scheduling comes to light.

Drugs are currently classified based on:

  • accepted medical use
  • abuse potential
  • dependency potential

Schedule I drugs have the highest potential for misuse and addiction, while schedule V drugs have the lowest potential for misuse and addiction. Schedule I drugs have no accepted medical value.

Schedule I Drugs

Schedule I drugs are substances that are determined to have a high potential for abuse, physical or psychological dependence, and have no accepted medical value.

Schedule I drugs include:

  • heroin
  • LSD
  • GHB
  • cannabis (marijuana)
  • molly/ecstasy/MDMA
  • methaqualone
  • peyote
  • psilocybin (magic mushrooms)

Read more about Schedule I Drugs

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Schedule II Drugs

Schedule II drugs have a high potential for abuse and physical or psychological dependence (i.e. addiction). They have limited medical value.

Schedule II drugs include:

  • cocaine
  • methamphetamine (meth)
  • hydrocodone (Vicodin, Percocet)
  • methadone
  • morphine
  • codeine
  • hydromorphone (Dilaudid)
  • oxycodone (OxyContin)
  • fentanyl
  • meperidine
  • dextroamphetamine (Dexedrine)
  • amphetamine (e.g. Adderall)
  • methylphenidate (Ritalin)

Read more about Schedule II Drugs

Schedule III Drugs

Schedule III drugs are drugs with moderate abuse potential. They have a low to moderate potential for physical or psychological dependence.

Schedule III drugs include:

  • products containing less than 90 mg of codeine (e.g. Tylenol with codeine)
  • testosterone
  • ketamine
  • anabolic steroids

Read more about Schedule III Drugs

Schedule IV Drugs

Schedule IV drugs are substances determined to have a low potential for abuse and a low potential for dependence.

Schedule IV drugs include:

  • phenobarbital
  • benzodiazepines (e.g. Xanax, Klonopin, Ativan, Valium)
  • flunitrazepam (i.e. roofies, Rohypnol)
  • zolpidem (Ambien)
  • tramadol (Ultram)

Read more about Schedule IV Drugs

Schedule V Drugs

Schedule V drugs are substances with medical use that are believed to have a very low potential for misuse. This includes some over-the-counter (OTC) medications.

Schedule V drugs include:

  • Robitussin AC
  • Lomotil
  • Motofen
  • pregabalin (Lyrica)

Read more about Schedule V Drugs

Why Does Drug Scheduling Matter?

The classification of a drug can be important for several reasons. Drug classifications are relevant to the work of law enforcement, lawmakers, and the federal government.

Drug scheduling can affect:

  • drug policy
  • federal regulation
  • criminal penalties (i.e. for use, possession, drug sales)
  • state laws

Drug Classifications By Drug Type

In addition to legal classifications, drugs can also be classified according to the class of drugs they belong to. This classification is largely dependent on how they affect the brain and body.

The seven drug types include:

  • stimulants
    • Example: cocaine
  • depressants
    • Example: Xanax
  • narcotic analgesics
    • Example: morphine
  • hallucinogens
    • Example: ecstasy
  • dissociative drugs
    • Example: ketamine
  • inhalants
    • Example: gasoline
  • cannabis (marijuana)

Stimulants and depressants are classified based on how they affect the central nervous system (CNS), by either stimulating CNS activity or slowing it down.

Certain narcotics, such as opioids, and cannabis can also depress central nervous system activity, although they are classified separately.

Drug Classification Terms To Understand

Here are definitions for some of the most important terms relevant to drug classification and scheduling.

Controlled substance: A controlled substance is a drug or chemical regulated by the federal government. This control regulates the use, possession, and manufacturing of the drug.

Abuse potential: Abuse potential generally refers to the likelihood that a drug may be misused.

According to the U.S. Food and Drug Administration (FDA), this can be based on:

  • whether the drug produces euphoria (or other changes in mood)
  • whether the drug affects central nervous system activity
  • whether the drug has hallucinogenic effects

The Controlled Substances Act (CSA) does not clearly define the term ‘abuse’. Identifying a drug’s abuse potential is left up to the classifying agency.

Dependency potential: This term is used to refer to how likely a drug is to cause physical dependence. Drugs with dependency potential may also be described as habit-forming.

Getting Help For Drug Abuse And Addiction

Searching for drug classifications is common among individuals affected by drug misuse. If you or a loved one is abusing drugs, we can help you find drug abuse treatment.

Call our helpline today to learn more about drug abuse or to find a drug abuse treatment program that’s right for you.

This page does not provide medical advice. See more

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Medically Reviewed by
Johnelle Smith, M.D on April 19, 2021
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