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How Are Drugs Classified?

Pharmacology, or the study of drugs and medications, is a complicated subject. One of the ways to make it easier to understand is to have a good knowledge of drug classification, or the system by which various drugs are grouped.

Drugs are categorized in a variety of ways. In the pharmaceutical industry, drugs are grouped according to their chemical activity or conditions that they treat. There are many reasons to classify drugs, ranging from understanding the usefulness of types of drugs to formulating treatment plans based on chemically similar drugs. In the world of illicit drug use, there are essentially 7 different types of drugs. Each has its own set of characteristics, dangers, and side effects.

Drug Classifications

Drug categories include:

  • Cannabis.
  • Depressants.
  • Dissociative anesthetics.
  • Hallucinogens.
  • Inhalants.
  • Opioids.
  • Stimulants.

For Drug Enforcement Agency (DEA) purposes, these drug classifications are further distilled into 5 categories. The DEA also refers to these as “schedules,” which depend on the drug’s accepted and authorized medical use or the drug’s dependency and misuse potential. The misuse rate of a drug is a determining factor when assigning a schedule. For example, Schedule I drugs are shown to have a high misuse rate and the potential to create significant psychological and physical dependence.1

The DEA defines physical dependence as developing when the body becomes habitually in need of a drug. Physical dependence is often exhibited both in the development of tolerance to a drug and in the withdrawal effects that might occur if a person stops using the drug. When a person builds a tolerance to a particular substance, it takes an increasingly larger amount of the substance to experience the same effects as once occurred with smaller amounts. Withdrawal develops with prolonged or excessive use and is experienced when a drug is sharply reduced or stopped. Often, withdrawal symptoms are excruciating and difficult to manage, which further encourages drug use.

Dependence on a drug is also associated with a variety of psychological and physical symptoms.  These include social problems, financial difficulty, and legal issues. Psychological dependence presents as the craving or intense need for a drug. When a person has become psychologically addicted, they might experience excessive and uncontrollable desires to use the drug. Ultimately, this can lead to drug-seeking behavior.

Legal Classification of Drugs

  • Schedule I: These drugs are defined as drugs that have no medical use and have a high potential for addiction and misuse. These include drugs such as ecstasy, heroin, and LSD.
  • Schedule II: These drugs have a high rate of potential misuse along with significant psychological or physical dependence. Examples of Schedule II drugs include cocaine, meth, and opioids.
  • Schedule III: These drugs have moderate to low potential for misuse. These include anabolic steroids, ketamine, and testosterone.
  • Schedule IV: These drugs have a low potential for dependence. Ambien, Ativan, and Valium are all Schedule IV drugs.
  • Schedule V: These drugs are medications usually used for analgesic, antidiarrheal, or antitussive purposes.

Chemical Classifications of Drugs

Many experts disagree on how drugs should be classified. This means that the same drug might be categorized differently under two different systems. Because of this, it is virtually impossible to create a set of defining drug classification standards. However, here are some of the most common.

  • Alcohol: Alcohol is one of the most widely misused substances across the world.2 It is legal to consume alcohol in the U.S., even though alcohol is a central nervous system (CNS) depressant. Alcohol can create lower inhibitions and cause severe long-term damage to the liver.
  • Benzodiazepines and barbiturates: These drugs function by interacting with a neurotransmitter called GABA (gamma-aminobutyric acid).3 They impact the body and mind differently but generally create calming and sedative effects. Often prescribed to treat a variety of psychiatric and sleep conditions, these drugs are highly addictive.
  • Cannabis: Cannabis is one of the most widely used drugs throughout the U.S.4 It affects the cannabinoid receptors in the brain. This drug comes in many different forms and affects each user differently.
  • Cocaine and other stimulants: These drugs accelerate the activity of the CNS making a person feel alert, energized, and focused, and alert for long periods.5 The converse reaction is that a person may feel angry, paranoid, and on edge.
  • Hallucinogens: By interacting with the CNS, this class of drugs alters the perception of reality, space, and time. They might cause a user to imagine situations or things that do not exist.6
  • Inhalants: Inhalants contain dangerous substances with psychoactive properties.7 Most inhalants are in household items (e.g., cleaning fluids, glue, spray paint), making them easily accessible by adolescents and children. They tend to be less addictive than other substances but are incredibly dangerous.
  • New psychoactive substances: This refers to anything that is lab-created to mimic naturally occurring drugs. This includes synthetic cannabis, lab-created ketamine, and more.
  • Opioids: Opioids derive from the opium poppy plant or synthetic versions that mimic the chemical structure of opium.8 This class of drugs interacts with neurotransmitters in the brain to block signals which can cause intense feelings of pleasure and reduce pain.

If you are or a loved one is suffering from addiction, it might feel like you are alone. The good news is treatment is available. A treatment facility can create a program tailored to your specific needs.

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