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Understanding Drug Classifications In the US

Dr. Gerardo Sison

Medically reviewed by

Dr. Gerardo Sison

March 29, 2019

It’s important to understand drug classifications in the U.S. to better comprehend misuse of substances, the risks associated with each drug, and how to avoid these risks by heeding the warnings that come with each drug’s legal schedule and the side effects associated with its chemical classification.

The U.S. government classifies drugs according to their chemical makeup, risk for abuse, risk for addictiveness, abuse rate, and potency. It is from these Schedules that legal consequences are determined. Knowing the drug schedules can help individuals avoid further consequences for misuse by instead seeking treatment for substance abuse or addiction.

What Are Drug Classifications?

Drug classifications were developed in 1970 after the U.S. government passed the Controlled Substances Act. The Act attempted to help regulate drugs and substances according to their potential for abuse and also by any medical benefits they can provide. In addition to the federal act, many states have passed their own acts determining statewide drug schedules as well.

Essentially, drug classifications provide information about each drug: what’s inside it and how the chemical composition affects the person using it, the drug’s abuse and addictiveness potential, current abuse rate, and the legal consequences of misusing it. Classifications of drugs in the U.S. are determined by Schedules, which are decided by the U.S. Drug Enforcement Administration (DEA).

How Are Drugs Classified In The U.S.?

The DEA explains that “drugs, substances, and certain chemicals used to make drugs are classified into five (5) distinct categories or schedules depending upon the drug’s acceptable medical use and the drug’s abuse or dependency potential.”

To better break down this definition, drugs are defined chemically according to how they affect the brain and body and classified legally according to their abuse potential and/or if they have a legitimate medical use.

Classification By Chemical Makeup

Drugs which are regulated by the DEA are those which act on the central nervous system, affecting the body and brain through chemical reactions within the brain. These drugs require regulation because they are capable of altering a person’s feelings, emotions, and perception of pain.

Chemical classifications for regulated drugs include:

  • Cannabis: Though recently legalized for medical use in many states, cannabis is an illicit drug derived from a plant, the most common form of which is marijuana. Despite new regulations for cannabis and its derivatives, the drug is still highly abused recreationally, remaining one of the most abused drugs in the U.S. and requiring some of the highest regulation.
  • Depressants: Central nervous system depressants work to depress reactions within the body by slowing functions in the brain and body, such as breathing and heart rates, and producing an overall sense of calm or sedation and heightened euphoria when abused. Depressant drugs include:
    • alcohol
    • anti-sleep medications: eszopiclone (Lunesta), gamma hydroxybutyrate, zaleplon (Sonata), and zolpidem (Ambien)
    • barbiturates: amobarbital sodium (Amytal), pentobarbital sodium (Nembutal) secobarbital sodium (Seconal), and phenobarbital (Luminal)
    • benzodiazepines: alprazolam (Xanax), diazepam (Valium), lorazepam (Ativan), temazepam (Restoril)
  • Hallucinogens: These drugs affect a person’s perceptions and their awareness of their surroundings, as well as their thoughts and feelings, by causing hallucinations or sensations and/or images which seem very real but do not exist. Hallucinogenic drugs include ayahuasca (Amazonian tea), DHT (chemical found in Amazonian plants), D-lysergic acid diethylamide (LSD), peyote, and psilocybin.
  • Inhalants: Inhalants are substances which are usually acquired through household or commercial products, but are typically not intended for consummation. These substances can be incredibly potent when inhaled and include solvents (such as those found in household cleaners), aerosol sprays, and gases (such as those found in medical anesthetics and nitrous oxide).
  • New Psychoactive Substances (NPS): This is the technical term given to drugs which are not yet regulated by the DEA or Controlled Substances Act, but which should be due to their risk for abuse and addictive potential. Many are designer drugs and may be synthetic, such as synthetic cathinones (or “bath salts) or synthetic cannabinoids. Those marketing NPS may refer to them as “legal highs”. Such drugs include ketamine, khat, kratom, and many plant-based substances.
  • Opioids: Next to alcohol and marijuana, opioids are the most commonly abused drugs in the U.S. They include:
    • prescription opioids: buprenorphine (Suboxone, Subutex) codeine, fentanyl, hydrocodone (Vicodin), hydromorphone (Dilaudid), oxycodone (OxyContin, Percocet, Roxicodone),
      oxymorphone (Opana), meperidine (Demerol), and methadone.
    • illicit prescription opioids: those which are diverted and/or sold for illegal use
    • heroin: illicit, man-made opioid sold in many forms and usually cut with other substances, which can be toxic and dangerous.
    • combination opioids: some of the most potent of the drug class, combination opioids increase an individual’s risk of overdose and include combinations like fentanyl-laced heroin. Opioids may also be combined with other drugs for specific effects, like cocaine-laced heroin, which also increases the risk of adverse effects.
    • designer drugs: some opioids are produced and sold on the street, such as heroin, while some are combined with other, more powerful opioids, such as grey death.
  • Stimulants: These drugs work to speed up the functions of the central nervous system, increasing heart and breathing rates, energy, and activity levels, and producing a sense of euphoria and a “rush” of happy feelings and state of elation when abused. Stimulant drugs include:
    • amphetamines: methylphenidate (Ritalin, Concerta), amphetamine
    • atomoxetine: Strattera
    • cocaine
    • crack cocaine
    • dextroamphetamine: Dexedrine
    • ecstasy, molly, and MDMA
    • methamphetamine, including the illicit, man-made form and the prescription Desoxyn

Knowing and understanding each drug’s abuse potential, possible side effects, risk for addiction, and risk for overdose is key to understanding how to regulate each drug and treat those affected by abuse of or addiction to it.

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Classifications By Legal Status (Schedules)

Chemical makeup is only one determining factor which influences how drugs are classified into Schedules. For example, one depressant drug may have far more abuse potential and addiction potential than another. One depressant drug could be a Schedule I drug (high potential for abuse and development of addiction), while another could be extremely low potential for abuse or development of addiction and be classified as Schedule IV.

Drug classifications in the U.S. have less to do with a chemical makeup of the drug and more to do with its abuse rate, abuse potential, and the risk of developing addiction associated with the drug.

There are five schedules of controlled substances, with Schedule I drugs containing the drugs which have the highest potential for abuse and highest rate of causing severe chemical dependency or addiction and Schedule V containing drugs with the lowest potential for abuse or dependency.

The following is a closer look at drug schedules in the U.S.

Schedule I

Schedule I drugs are those which are determined by the DEA to have no legitimate medical use and which have a high potential for abuse and risk for addiction or physical dependence.

Schedule I drugs include:

  • heroin
  • LSD
  • marijuana (cannabis)
  • ecstasy
  • peyote.

Schedule II

Schedule II drugs are those which may still have a medical use, but which have a high potential for abuse and a high potential to lead to addiction or dependence.

Schedule II drugs include:

  • opioids with less than 15 milligrams of hydrocodone (Vicodin)
  • amphetamine (Adderall, Ritalin)
  • cocaine
  • fentanyl
  • hydromorphone (Dilaudid)
  • meperidine (Demerol)
  • methamphetamine
  • methadone
  • oxycodone (OxyContin).

Schedule III

Drugs classified as Schedule III are considered to have a low to moderately low potential for abuse and low risk for development of addiction or dependence.

Schedule III drugs include:

  • opioids with less than 90 milligrams of codeine (Tylenol with codeine)
  • anabolic steroids
  • ketamine
  • testosterone.

Schedule IV

Drugs in Schedule IV classification have a low risk for abuse and low risk for development of addiction or dependence.

Schedule IV drugs include:

  • alprazolam (Xanax)
  • diazepam (Valium)
  • dextropropoxyphene (Darvocet)
  • lorazepam (Ativan)
  • tramadol (Ultram)
  • zolpidem (Ambien).

Schedule V

Schedule V drugs are those which have a lower abuse potential than those in Schedule IV, usually involving drugs with limited narcotic makeups, such as Robitussin AC and Lyrica.

*The drugs mentioned are only some of the most commonly abused drugs within each Schedule classification. For a comprehensive list of drugs in each Schedule, see the DEA website.

Consequences Of Abusing Controlled Substances

Abuse of controlled substances can cause both personal and legal consequences. Drugs with a higher potential for abuse and risk of addiction, such as Schedule I and II drugs, can quickly lead to addiction, physical dependence, and increased risk of overdose due to repeated misuse.

Each drug comes with its own risk of side effects depending on the drug, method of administration, the overall health of the person, frequency and duration of abuse, and any co-occurring substance abuse. The more a person abuses any substance the more he or she is at risk for adverse effects, development of addiction and/or dependence, and risk of overdose.

Should a person escape detrimental effects to their health, addiction eventually affects family and friends close to the person and can affect job and school performance, finances, relationships, and more.

If a person is caught misusing or in possession of controlled substances, they can face hefty legal consequences, which may include jail time, fines, or court-ordered rehab time. Seeking treatment for drug abuse or addiction, and helping a person conquer these issues before experiencing life damage, is always a more beneficial option.

Treatment For Drug Misuse

Treatment for drug misuse, abuse, and addiction will depend on a number of factors. Some of these include the drug of abuse, frequency and duration of abuse, the person and any unique treatment needs they may have (such as a coexisting substance use disorder or co-occurring mental health disorder), and more.

Any person experiencing prolonged substance abuse, addiction, or physical dependence will benefit most from inpatient treatment, which allows a person to seek care within a rehab center. Here, individuals have access to 24-hour medical support, medically supervised detoxification, medication when needed, evidence-based and formal treatments, and everything they need to begin recovery. To learn more about treatment options for drug abuse in the U.S., speak to one of our specialists today.

National Institute on Drug Abuse - Hallucinogens, Inhalants, Marijuana as Medicine, Prescription CNS Depressants

Substance Abuse and Mental Health Services Administration - Stimulants

U.S. Food & Drug Administration - Opioid Medications

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