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Drug Classes

Drug Classes

Drug Classes and Abuse

Knowing the drug class of a substance is important information when dealing with substance abuse questions. Drug abuse is a serious problem around the world, and the United States is no exception. According to the National Institute on Drug Abuse (NIDA), the abuse of legal and illegal psychoactive drugs costs the U.S. $740 billion each year in lost productivity and in costs associated with law enforcement and health care.1 But the greater cost of drug abuse can’t be calculated in dollars and cents. Drug and alcohol abuse affects not only the lives of people with substance abuse disorders but also the lives of everyone close to them. It disrupts the functioning of the family system, damages relationships, and may fuel poverty, mental illness, and abuse.

A 2015 study by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) found that four percent of Americans had met the criteria for a substance use disorder in the preceding year, and 10 percent had had a substance use disorder at some point in their lives.2 All told, more than 23 million Americans have struggled with the problematic use of drugs, including alcohol. Unfortunately, fewer than 20 percent of people who have a drug or alcohol use disorder get the help they need to recover successfully.

Drugs of Abuse, Defined

Drugs of abuse are psychoactive drugs that act on the central nervous system. They alter the normal function of the brain by disrupting the communication between neurons, or brain cells. Different psychoactive drugs act on different neurotransmitters, or brain chemicals, to produce different effects. One thing all psychoactive drugs have in common is that they act on the dopamine system in the brain. Dopamine is the neurotransmitter that produces feelings of pleasure, and it’s a major player in the brain’s memory, learning, and reward centers.

Substance Use Disorders, Explained

Whether a psychoactive drug is legal (like alcohol or cough medicine) or illegal (like heroin or cocaine), abusing it can have serious consequences, including addiction and dependence.

Drug abuse, addiction, and dependence are terms that are often used interchangeably, but they aren’t the same.


Drug abuse is the act of using any psychoactive drug in a risky way or in a way that causes problems with relationships, finances, health, or legal status due to substance abuse. Prescription drug misuse is a common form of drug abuse that involves either using prescription drugs in a way other than that which was prescribed or taking someone else’s prescription medication. Both types of prescription drug abuse are illegal.


Addiction results from changes in brain function due to heavy drug abuse, which may cause the learning, reward, and memory systems of the brain to communicate in a way that causes intense cravings. People who are addicted engage in compulsive drug use despite negative consequences. Whether an addiction will develop depends on a number of factors, including genetic, biological, environmental, cultural, and social factors. Genetics accounts for about half the risk of developing an addiction.


Dependence also results from brain changes caused by heavy drug abuse. As substance abuse escalates, the brain alters the function of neurotransmitters in order to compensate for the effects of the drugs. This causes tolerance, which means that larger doses of the drug are required in order to get the desired effects. At some point, the brain may adjust and become more comfortable when drugs are present. Then, when drug use is suddenly discontinued, normal neurotransmitter function returns, causing physical withdrawal symptoms. These symptoms vary depending on the drug, but in some cases, withdrawal can be dangerous or fatal.

Since 2013, substance abuse, addiction, and dependence have been diagnosed under the umbrella of “substance use disorders” (SUDs). Eleven criteria are used to diagnose substance use disorders, which are classified as mild, moderate, or severe, depending on the number of criteria met.

Here, we look at the different classes of psychoactive drugs that can cause a substance use disorder.


Central nervous system stimulants speed up the body’s systems. Drugs in this class include nicotine and caffeine, which are widely used and generally accepted as more or less safe when used in moderation.

Other stimulants are more harmful and, therefore more tightly regulated. Cocaine, methamphetamine, and prescription stimulants like Adderall and Ritalin are listed under Schedule II of the Controlled Substances Act. Schedule II drugs are those that have a high potential for abuse but that also have medical value.

Stimulants are highly addictive, significantly increasing the activity of dopamine as well as increasing the activity of other feel-good brain chemicals like serotonin and norepinephrine.


Cocaine is derived from the coca leaf. It’s a white powder that is typically snorted, but it can also be mixed with water and injected. Crack cocaine is cocaine in rock form, and it’s smoked through a small glass pipe. Cocaine produces a short-lived high that produces euphoria and increased energy. Long-term cocaine abuse can lead to heart problems, seizures, strokes, and comas.

According to the National Survey on Drug Use and Health (NSDUH), around 1.5 million Americans aged 12 and older reported past-month cocaine use in 2014, and around 913,000 people met the DSM-V criteria for a cocaine use disorder that year. Cocaine is involved in around 40 percent of drug-related visits to the emergency department, and it’s responsible for more than 5,000 overdose deaths each year.

The good news is that cocaine use among teenagers has declined significantly since peak use in the late 1990s. In 2014, according to the NSDUH, just 1.1 percent of high school seniors and 0.8 percent of 10th graders had used cocaine in the past month.


Commonly known as meth, ice, crystal, or speed, methamphetamine is a powerful and highly addictive stimulant. Most meth in the U.S. comes from Mexico, but it’s also made inside the US in clandestine meth labs with ingredients like pseudoephedrine and a range of dangerous toxic chemicals. Meth lab explosions often result in serious injury or death and also cause devastating house fires.

Meth is smoked, snorted, or injected. Similarly to the cocaine high, the euphoria and heightened energy of the meth high is short-lived. This type of drug abuse often results in binging on meth for days, foregoing sleeping, and eating. Long-term meth abuse causes problems like extreme weight loss, malnutrition, skin lesions, severe dental problems, and extreme paranoia.

The National Institute on Drug Abuse reports that around 15 percent of overdose deaths in 2017 involved methamphetamine. Half of those deaths also involved fentanyl, a synthetic opioid that is sometimes added to street meth unbeknownst to the user. Meth overdose typically causes heart attack, stroke, or other organ problems.

Prescription Stimulants 

Prescription stimulants like dextroamphetamine (Dexedrine), amphetamine (Adderall), and methylphenidate (Ritalin and Concerta) are prescribed for ADHD and certain sleep disorders, but they’re commonly abused. Of the 16 million American adults who used prescription stimulants during the previous year, five million misused them, and around 400,000 had substance use disorders involving prescription stimulants, according to NIDA.3

More than half of people who misused prescription stimulants reported that they did so hoping to enhance their cognitive abilities, including improving concentration and alertness. However, research shows that such improvements from prescription stimulants are minimal and inconsistent. Still, prescription stimulant misuse is particularly prevalent among college students, with 17 percent of students on average abusing these medications each year, according to an article published in the journal Experimental and Clinical Psychopharmacology.


Central nervous system depressants slow down the body’s systems. Alcohol is the most commonly used depressant and the most abused drug in the United States. Prescription depressants treat anxiety and sleep disorders.


Binge drinking is the most common form of drug abuse in the U.S. Binge drinking involves consuming enough alcohol in two hours to increase blood alcohol content to .08 percent. For men, the typical amount required to produce this effect is five drinks, and for women, it’s four. According to the National Institute on Alcohol Abuse and Alcoholism (NIAAA), 26.4 percent of adults aged 18 and over reported binge drinking in the past month in 2017.4 Nearly seven percent of all American adults reported past-month heavy alcohol abuse, defined as binge drinking on five or more days in the past month, in that year.

Around 15 percent of people who abuse alcohol become addicted to it. According to the 2017 NSDUH, 14.1 million American adults had an alcohol use disorder in that year. However, only 6.5 percent of those with a past-year alcohol use disorder received treatment.

Long-term alcohol abuse has serious health consequences. An estimated 88,000 people die of alcohol-related causes each year, according to the NIAAA. This number doesn’t include the nearly 10,000 driving fatalities which involve alcohol.


Benzodiazepines, commonly called “benzos,” are prescription sedatives used to treat conditions like anxiety, seizures, muscle spasms, and insomnia. These drugs include alprazolam (Xanax), clonazepam (Klonopin), and diazepam (Valium.) Benzodiazepines enhance the effects of the neurotransmitter GABA-A, which is responsible for feelings of calm and relaxation.

Benzodiazepines are safe and effective when used as prescribed for a short amount of time, typically four weeks. But prolonged use or abuse can lead to addiction and dependence. Withdrawal from benzodiazepines may cause dangerous shifts in blood pressure and heart rate, and in some cases, quitting cold turkey can be fatal.

According to the American Psychiatric Association, 12.6 percent of American adults used benzodiazepines in the past year, with misuse accounting for over 17 percent of overall use. When they’re misused, benzodiazepines are often taken with alcohol or opioids, combinations that increase the risk of overdose and death. Long-term benzodiazepine abuse can lead to substantial cognitive impairment and an increased risk of falls and hip fractures in older users.

Non-Benzodiazepine Sedative Hypnotics​

More commonly known as sleeping pills, sedative-hypnotic drugs like zolpidem (Ambien), eszopiclone (Lunesta), and zaleplon (Sonata) are prescribed for insomnia. While they’re considered far safer and less addictive than benzodiazepines, these drugs still have potential for abuse. Additionally, because of increasing reports of bizarre behavioral effects produced by these drugs, regulatory agencies have issued warnings and restrictions on prescribing and using them.


Barbiturates have powerful sleep-inducing effects. The abuse of barbiturates was a common and serious problem before benzodiazepines, which are much safer, replaced these dangerous drugs in the 1980s. Today, barbiturates are primarily used as anesthetic and anti-convulsant medications rather than treatments for anxiety and sleep problems. Barbiturate abuse and overdose deaths have decreased significantly as prescriptions have dwindled, but these drugs are still available on the street. According to NIDA, barbiturates caused 409 overdose deaths in 2016, 21 percent of which also involved synthetic opioids.


Opioids, also known as opiates, are drugs that are derived from morphine, which occurs naturally in some varieties of the poppy plant. Opioids produce feelings of intense euphoria and well-being. Currently, the United States is battling an opioid epidemic that claims 115 lives each day due to overdose. Opioid abuse is the number-one cause of preventable death among 18- to 35-year-olds, according to the Centers for Disease Control. An estimated 2.5 million Americans are currently addicted to opioids.

The greatest long-term danger of opioid abuse is an extremely high risk of overdose, especially when heroin or painkillers are used with alcohol, benzodiazepines, or barbiturates. Opioid abuse also increases the risk of HIV/AIDS, skin and blood infections, and organ damage.

Prescription Painkillers

Opioid painkillers treat mild, moderate, and severe pain by reducing the intensity of pain signals that reach the brain. Opioid pain medications are listed under Schedule II of the Controlled Substances Act. The most commonly prescribed and abused painkillers are oxycodone (OxyContin and Percocet) and hydrocodone (Lortab, Vicodin). The United States accounts for 81 percent of the world’s oxycodone market and 100 percent of the world’s hydrocodone market.

Around two million Americans are addicted to opioid painkillers. To address the problem, manufacturers have created abuse-resistant formulations for these medications. For example, new technologies make it possible to produce a crush-proof pill to prevent snorting and a pill that turns gelatinous when it’s dissolved to prevent injecting. Still, users have found ways to abuse painkillers despite these safeguards.


Heroin is an illegal opioid that’s listed as a Schedule I drug, which means that it has a very high potential for abuse but no medical value. Heroin is typically smoked or injected, but it can also be snorted. According to NIDA, around 23 percent of people who abuse heroin become addicted to it.

Around 600,000 Americans currently have an opioid use disorder involving heroin. NIDA points out that around 86 percent of people who are addicted to heroin started using prescription painkillers first. Some make the switch because heroin is cheaper and easier to get, and also because it doesn’t have the anti-abuse features which many opioid painkillers have.


Cannabinoids are chemical compounds that act on cannabinoid receptors in the brain to alter the release of certain neurotransmitters. The best-known cannabinoid is tetrahydrocannabinol, or THC, which is the psychoactive compound in the cannabis plant.


Marijuana is the dried leaves, flowers, and stems of the cannabis plant. Even as the federal government classifies marijuana as a Schedule I drug, many states are decriminalizing or legalizing this drug for both medical and recreational use. Some marijuana proponents say that marijuana is safe and non-addictive, but while it’s not as dangerous or addictive as other psychoactive drugs, it does have the potential to cause addiction and dependence. According to new data from NIDA, around 30 percent of people who use marijuana may have a marijuana use disorder to some degree.5 People who start using marijuana before the age of 18 have a four- to-seven-fold increase in the risk of developing a marijuana use disorder.

Marijuana is the most commonly used psychoactive drug in the U.S. after alcohol. In 2017, one in seven Americans used marijuana. Younger people between 18 and 34 report the highest use, with more than 11.8 million young adults using marijuana in 2018, according to NIDA. The effects of marijuana include an altered sense of time, changes in mood, impaired memory, and altered senses.

Long-term effects of marijuana use include lung problems from smoking it and mental health problems like anxiety and depression.

Synthetic Marijuana 

Synthetic marijuana contains human-made chemicals and is marketed as a safe, legal alternative to marijuana. Sold under names like K2, Spice, and Kronic, synthetic marijuana acts on the same brain cell receptors as THC and produces effects similar to those of natural marijuana, including relaxation and an elevated mood. However, it can produce severe effects that aren’t associated with cannabis, including violent behavior, extreme anxiety, suicidal thoughts, kidney damage, and seizures. The effects of synthetic marijuana can be unpredictable and dangerous, and they have been associated with an increasing number of deaths, according to NIDA.


Drugs classified as hallucinogens alter perceptions, awareness, thoughts, and feelings. They can produce hallucinations and cause people who use them to feel disassociated from their bodies and environments. Historically, hallucinogens have been used in religious and healing rituals. In modern times, people report using them to get high, have fun, experience spiritual awakenings, or just feel different.

How Hallucinogens Work

Hallucinogens work by temporarily disrupting the communication between systems in the brain and spinal cord. Some hallucinogens interfere with the neurotransmitter serotonin to cause mood changes and changes in sensory perceptions. Dissociative hallucinogens interfere with the neurotransmitter glutamate, which regulates the perception of pain and emotions and affects learning and memory.

Long-term Effects of Hallucinogens

Long-term use of hallucinogens can cause persistent psychosis, which includes visual disturbances, paranoia, mood changes, and disorganized thinking. Flashbacks are common among people who heavily abuse hallucinogens. During a flashback, a person who is not currently using the drug will experience the sensations of being on the drug; these symptoms may be mistaken for symptoms of a stroke or a brain tumor.

There are two types of hallucinogens. Psilocybin mushrooms and LSD are examples of “classic hallucinogens,” a group that also includes DMT, peyote, and 251-NBOMe. The other category is dissociative drugs. These include PCP, ketamine, DXM, and salvia. Dissociative drugs cause users to feel disconnected from their bodies and environments and can also lead to feelings of loss of control. Long-term use of these hallucinogens can cause speech problems, memory loss, anxiety, depression, and suicidal thoughts. The most commonly used hallucinogens are LSD and psilocybin mushrooms.


D-lysergic acid diethylamide, or LSD, is a powerful and popular mind-altering hallucinogen. LSD is commonly known simply as “acid,” since it’s made from lysergic acid, which occurs naturally in a fungus that grows on certain grains. LSD is listed under Schedule I of the Controlled Substances Act.

Around 0.1 percent of the total American population reported having used LSD in the past month in 2014, while 0.3 percent of 12- to 17-year-olds reported past-month use in that year, according to the Drug Policy Alliance.

Psilocybin Mushrooms

Psilocybin mushrooms, known as “shrooms” or “magic mushrooms,” are dried and eaten to produce mild hallucinations. Although these mushrooms are listed on Schedule I of the Controlled Substances Act, a number of recent studies show that psilocybin may have therapeutic effects for some mental health disorders, including suicidal ideation and depression.

Other Drug Classes

Anabolic Steroids

Anabolic steroids are synthetic versions of testosterone, a male sex hormone. On the street, steroids are known as gear, juice, roids, and stackers. While steroids are prescribed to treat hormonal issues and muscle loss from diseases like cancer and AIDS, they’re commonly abused by bodybuilders and athletes trying to boost performance and improve their physique.

Anabolic steroids work differently on the brain than other psychoactive drugs. They don’t activate the reward system and cause a “high.” However, they do alter brain function, causing problems like paranoid jealousy, extreme irritability, aggression, delusional thinking, and impaired judgment. Long-term steroid misuse can lead to kidney failure, liver damage, tumors, an enlarged heart, and high blood pressure.

OTC Drugs

Some over-the-counter drugs, which can be purchased without a prescription, are misused in order to produce highs. Dextromethorphan, or DXM, is a cough suppressant found in some OTC cold medicines, which may be misused with alcohol and marijuana. In large doses, DXM has hallucinogenic effects.

Another commonly abused OTC drug is loperamide, an anti-diarrheal medication. Loperamide is an opioid, but it doesn’t act on the brain’s opioid receptors as other opioids do. However, in large amounts, loperamide can have effects similar to other opioids.

It’s possible to overdose on OTC medications, and it’s possible to develop a substance use disorder involving them. Over-the-counter medications should always be taken as directed on the packaging or as directed by a physician.

Treating Substance Use Disorders

Treatment for a substance use disorder involves a period of detox, during which all traces of the drug leave the body so brain function can return to normal. After detox, treating the addiction involves a variety of therapies that help individuals change their mindsets, restore order to their lives, and learn to cope with negative emotions, cravings, stress, and other relapse triggers. Treatment helps people find purpose and meaning in a life of sobriety.

Hope is the foundation of recovery, according to the Substance Abuse and Mental Health Services Administration. As long as patients hold on to hope for a better future free of addiction, recovery is possible. Treatment works for most people who fully engage with their treatment plan. Regardless of the type of drug, the severity of addiction, or the damage the drug has done to a person’s life, long-term recovery is always within reach of those who reach out for help.