How Are Drugs Classified?
Drugs are classified chemically according to how they affect the brain and the body. Common classifications include stimulants, depressants, hallucinogens, and opioids. Additionally, the DEA legally classifies drugs into schedules (I, II, III, IV, and V) based on their medical use and potential for abuse and dependence.
Drugs can be categorized in a number of ways. In the world of medicine and pharmacology, a drug can be classified by its chemical activity or by the condition that it treats. Anticonvulsant medications, for example, are used to prevent seizures, while mucolytic drugs break down mucus and relieve congestion.
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With regard to addiction treatment and rehabilitation, the drug classifications used most often are the following five classes regulated by the Controlled Substances Act:
- Anabolic steroids
All of these drugs, with the exception of anabolic steroids, are considered to be psychoactive – meaning they affect one or more of the mental faculties including mood, feelings, thoughts, perception, memory, cognition, and behavior. Additionally, use of these drugs can be associated with a host of physical, mental health, and personal complications, including alcoholic liver cirrhosis, cannabis-induced psychosis, social problems like stigma, occupational difficulties, financial problems, and even legal problems.
According to the U.S. Drug Enforcement Administration (DEA), substances from any of these classes may lead to the development of chemical dependence in one or both of the following forms:
- Physical dependence to a drug suggests that the body has become habituated to the presence of a drug. Consequently, physical dependence is reflected in both the development of tolerance and the presence of a withdrawal syndrome. Tolerance refers to reduced effects compared to what was experienced with a previous amount of the substance. Withdrawal develops when excessive or prolonged use of a drug is sharply reduced or stopped. The onset of withdrawal often prompts the dependent individual to resume use of the drug (or one similar to it) to avoid withdrawal. For example, withdrawal symptoms such as shaking, sweating, nausea, vomiting, or seizures may occur once alcohol use is stopped after regular or excessive use.
- Psychological dependence is manifested in the form of craving for a drug. A person with psychological dependence has an excessive, irresistible, uncontrollable desire to use the drug. Psychological dependence may not cause physical symptoms, but can lead to drug-seeking behavior.
Chemical Classifications of Drugs
Each of the regulated drugs that act on the central nervous system or alter your feelings and perceptions can be classified according to their physical and psychological effects. The different drug types include the following:
- Depressants. Drugs that suppress or slow the activity of the brain and nerves, acting directly on the central nervous system to create a calming or sedating effect. This category includes barbiturates (phenobarbital, thiopental, butalbital), benzodiazepines (alprazolam, diazepam, clonazepam, lorazepam, midazolam), alcohol, and gamma hydroxybutyrate (GHB). Depressants are taken to relieve anxiety, promote sleep and manage seizure activity.
- Stimulants. Drugs that accelerate the activity of the central nervous system. Stimulants can make you feel energetic, focused, and alert. This class of drugs can also make you feel edgy, angry, or paranoid. Stimulants include drugs such as cocaine, crack cocaine, amphetamine, and methamphetamine. According to the recent World Drug Report published by the United Nations Office on Drugs and Crime, amphetamine-derived stimulants like ecstasy and methamphetamine are the most commonly abused drugs around the world after marijuana.
- Hallucinogens. Also known as psychedelics, these drugs act on the central nervous system to alter your perception of reality, time, and space. Hallucinogens may cause you to hear or see things that don’t exist or imagine situations that aren’t real. Hallucinogenic drugs include psilocybin (found in magic mushrooms), lysergic acid diethylamide (LSD), peyote, and dimethyltryptamine (DMT).
- Opioids. These are the drugs that act through the opioid receptors. Opioids are one of the most commonly prescribed medicines worldwide and are commonly used to treat pain and cough. These include drugs such as heroin, codeine, morphine, fentanyl, hydrocodone, oxycodone, buprenorphine, and methadone.
- Inhalants. These are a broad class of drugs with the shared trait of being primarily consumed through inhalation. Most of the substances in this class can exist in vapor form at room temperature. As many of these substances can be found as household items, inhalants are frequently abused by children and adolescents. These include substances such as paint, glue, paint thinners, gasoline, marker or pen ink, and others. Though ultimately all of these substances cross through the lungs into the bloodstream, their precise method of abuse may vary but can include sniffing, spraying, huffing, bagging, and inhaling, among other delivery routes.
- Cannabis. Cannabis is a plant-derived drug that is the most commonly used illicit drug worldwide. It acts through the cannabinoid receptors in the brain. Cannabis is abused in various forms including bhang, ganja, charas, and hashish oil.
- New psychoactive substances (NPS). These are drugs designed to evade the existing drug laws. Drugs such as synthetic cannabinoids, synthetic cathinones, ketamine, piperazines, and some plant-based drugs such as khat and kratom are examples of NPS.
Legal Classifications of Drugs
The Controlled Substances Act established five classifications, or schedules, for drugs regulated by law. According to the DEA, these classifications are broken down based on their potential for abuse and if they have a legitimate medical use:
- Schedule I include the drugs that have a high potential for abuse, that have no currently accepted medical use in treatment in the United States, and that there is a lack of accepted safety for use of the drug under medical supervision. Drugs such as cannabis, ecstasy, GHB, heroin, LSD, mescaline, and methaqualone are included in Schedule I.
- Schedule II includes drugs that have a high potential for abuse, have currently accepted medical use in treatment in the United States or currently accepted medical use with severe restrictions, and that the abuse of may lead to severe psychological or physical dependence. Drugs such as amphetamine, cocaine, fentanyl, hydromorphone oxycodone, and hydrocodone are included in Schedule II.
- Schedule III includes drugs that have a potential for abuse less than the drugs or other substances in schedules I and II, have a currently accepted medical use in treatment in the United States, and that the abuse of may lead to moderate or low physical dependence or high psychological dependence. Drugs such as anabolic steroids, buprenorphine, and ketamine are included in Schedule III.
- Schedule IV includes drugs that have a low potential for abuse relative to the drugs or other substances in schedule III, have a currently accepted medical use in treatment in the United States, and that the abuse of may lead to limited physical dependence or psychological dependence relative to the drugs or other substances in schedule III. Drugs such as benzodiazepines, modafinil, and tramadol are included in Schedule IV.
- Schedule V includes drugs that have a low potential for abuse relative to the drugs or other substances in schedule IV, have a currently accepted medical use in treatment in the United States, and that the abuse of may lead to limited physical dependence or psychological dependence relative to the drugs or other substances in schedule IV. Drugs such as diphenoxylate (in combination with atropine), lacosamide, and pregabalin are included in Schedule V.
The legal and personal consequences of misusing controlled substances can be severe. With your doctor’s help, you can use these drug classifications as guidelines to help you determine if a medication or substance is both safe and beneficial.