What are Drugs: Definition, Usage, Effects and Types

Last Updated: January 20, 2025

Drugs are substances that alter the body’s normal functioning, impacting physical, mental, and emotional states. People use drugs for a variety of reasons, from seeking relief from physical pain and mental distress to enhancing performance or experiencing pleasure. While some drugs are legally prescribed and beneficial for health, others are used recreationally or illegally, which leads to misuse and harmful effects.

Individuals (adults, college students, elderly) turn to drugs for reasons such as managing stress, peer influence, emotional escape, pain management or the desire to enhance social interactions. According to the National Center for Drug Abuse Statistics in “Drug Abuse Statistics” 50% of people 12 and older have used illicit drugs at least once.

Drugs are categorized into several types: illegal drugs, prescription drugs, alcohol and psychoactive drugs. These categories reflect the varied purposes and effects drugs have, and each type carries its own set of risks and regulations.Drugs are taken into the body in several ways, including orally as pills or liquids, injected directly into the bloodstream, inhaled or smoked, or absorbed through mucous membranes. Each method of intake affects how quickly the drug reaches the brain and how intense its effects are. This variety in drug types and methods of use illustrates the wide range of experiences and risks associated with drug consumption.

The effects of drugs vary widely based on their type and the user’s personal health, including physical changes like increased heart rate or liver damage and psychological effects such as mood swings and addiction. Drug misuse accounts for nearly 1% of the global disease burden according to the World Health Organization in 2022, primarily affecting mental health and increasing the risk of chronic health issues.

Effective treatment options include medical detoxification, therapy, and support groups, which target both the physical and psychological aspects of addiction. Rehabilitation centers integrate these methods, using a combination of medication-assisted treatment (MAT) and cognitive behavioral therapy (CBT) to address addiction’s root causes and support long-term recovery according to the Substance Abuse and Mental Health Services Administration in 2021.

Table Of Contents:

What is the Definition of a Drug?
Why Do People Use Drugs?
What are the Methods of Taking Drugs?
How Do Drugs Affect the Mind?
What Drugs are Commonly Abused?
What are the Categories of Drugs?
What is Drug Abuse?
How Are Drugs Made?
What are the Risks of Taking Drugs?
What are Drugs that are Used for Treatment?
How Do Drugs Function?

What is the Definition of a Drug?

The definition of a drug is a chemical substance that, when taken into the body, actively alters its natural processes, changing how the brain, nervous system, and other organs function. They are used for therapeutic reasons, such as managing pain or treating chronic conditions, or recreationally to achieve mind-altering effects. Drugs influence various bodily systems, including the nervous and cardiovascular systems, depending on their chemical structure and intended purpose.

Drugs are classified into categories based on their effects and composition. The main classifications include stimulants, depressants, opioids, hallucinogens, medications and cannabinoids. This classification system reflects the core effects of each type and helps in understanding their medical or recreational uses.

Over the past year, 59.3 million people (21.4%) reported using illegal drugs or misusing prescription drugs, while half of Americans in this age group—about 138.5 million—reported illicit drug use at some point in their lives. Drug disorders affect 25.4% of current illegal drug users, with 24.7% of these individuals experiencing an opioid disorder, which includes misuse of prescription pain relievers and heroin according to Drug Abuse Statistics.org and Substance Abuse and Mental Health Services (SAMHSA). These figures highlight the ongoing public health challenges associated with drug use and addiction in the U.S.

Why Do People Use Drugs?

People use drugs because they seek to alter their physical or mental state for various reasons. Some individuals use drugs for medical purposes, such as treating pain or managing health conditions, while others use them recreationally to experience pleasure or escape from stress. Certain drugs are more appealing than others due to their specific effects, availability, or social acceptance.

People use drugs for the following reasons:

Medical Treatment: Managing pain, controlling symptoms of illnesses, or treating mental health disorders with prescribed medications. Approximately 18% of Americans used at least one prescription medication for mental health treatment in 2019 according to Wang, K et. al. “Depression and Substance Use: Towards the Development of an Emotion Regulation Model of Stigma Coping”published in Substance Use & Misuse.
Recreational Enjoyment: Experiencing euphoria, enhanced sensations, or altered perceptions during social activities. In 2021, 61.2 million Americans aged 12 or older (21.9% of the population) were past-month users of illicit drugs according to the 2021 National Survey on Drug Use and Health (NSDUH) conducted by the Substance Abuse and Mental Health Services Administration (SAMHSA).
Coping with Stress or Emotions: Alleviating anxiety, depression, or emotional distress through temporary escape. Approximately 9.5 million adults aged 18 or older (3.7% of all adults) had both a substance use disorder and any mental illness in 2019″ comes from the 2019 National Survey on Drug Use and Health (NSDUH) conducted by the Substance Abuse and Mental Health Services Administration (SAMHSA).
Peer Influence: Using drugs to fit in with a group or due to social pressure from friends or acquaintances. In 2022, 3.5% of college students reported using Adderall without a prescription in the past year according to the “Monitoring the Future National Survey Results on Drug Use” written by Schulenberg, J et. al. 2023.
Performance Enhancement: Improving athletic abilities, cognitive functions, or productivity with stimulants or other substances. The prevalence of doping in recreational sports was found to be 1.6% overall, with higher rates in certain categories. Specifically, in “Games” sports, the estimated doping prevalence was 6.9% according to “Recreational Athletes’ Use of Performance-Enhancing Substances” and published in the Journal of Sports Medicine and Physical Fitness.
Curiosity and Experimentation: Trying drugs out of a desire to experience new sensations or satisfy personal curiosity. A 2011 study found that 74.0% of treatment admissions aged 18 to 30 years reported initiating alcohol or drug use at the age of 17 or younger according to Strashny A. in “Age of Substance Use Initiation Among Treatment Admissions Aged 18 to 30” published by theSubstance Abuse and Mental Health Services.
Cultural or Religious Practices: Participating in traditional ceremonies or rituals that involve the use of psychoactive substances. The most common drugs in the historical religions are cannabis and alcohol according to “Religion and drugs” published by Wikipedia.

The appeal of certain drugs over others is influenced by factors like the intensity of their effects, how quickly they act, societal norms, legal status, and perceived risks. For example, alcohol and tobacco are widely used because they are legal and socially accepted in many cultures, whereas other substances are preferred for their stronger or more immediate effects despite legal restrictions.

What are the Methods of Taking Drugs?

The methods of taking drugs are oral, inhalation, injection, topical, and sublingual/buccal. Injection is the most severe method, delivering drugs directly into the bloodstream for rapid, intense effects, with higher risks of overdose and infection. In contrast, oral ingestion is the most common and standard approach, where drugs pass through the digestive system, resulting in a slower, more controlled onset. The choice of method affects the speed and intensity of effects, balancing user needs with potential risks.

The methods of taking drugs are detailed below:

Oral: Drugs are swallowed and absorbed through the digestive system, typically taking longer to reach the bloodstream. The onset is slower, but effects last longer due to gradual absorption.
Inhalation: Drugs are inhaled into the lungs, where they quickly enter the bloodstream. This method provides a fast onset, within seconds, and is commonly used with substances like nicotine, cannabis, or inhalants.
Injection: Drugs are injected directly into the bloodstream (intravenous), muscles (intramuscular), or under the skin (subcutaneous). Injection produces rapid effects, especially with intravenous methods, as the drug bypasses absorption barriers, leading to intense and immediate effects.
Topical: Drugs are applied directly to the skin, where they are absorbed locally. This method is used for creams or patches for pain relief or hormone delivery. Absorption is generally slower and localized, affecting only the application area unless the drug is designed for systemic absorption.
Sublingual/Buccal: Drugs are placed under the tongue (sublingual) or in the cheek pocket (buccal), where they dissolve and directly enter the bloodstream through mucous membranes. This method provides a relatively quick onset without the drug needing to pass through the digestive system.

Hope Without Commitment

Find the best treatment options. Call our free and confidential helpline

(800) 913-1755

Most private insurances accepted

Who Answers

How Do Drugs Affect the Mind?

Drugs affect the mind by altering brain chemistry, specifically through their interaction with neurotransmitters, which are chemicals that control mood, perception, and thought. By increasing or decreasing the activity of certain neurotransmitters, drugs create feelings of euphoria, relaxation, heightened alertness, or altered sensory experiences. Long-term drug use alters brain structures involved in motivation, memory, and behavioral control, leading to compulsive drug-seeking behaviors that define addiction according to Volkow, N. D. (2020). The Science of Drug Use and Addiction: The Basics. published by the National Institute on Drug Abuse. Chronic drug use disrupts the brain’s dopamine system, making it harder for individuals to experience pleasure without the drug.

Short-Term Effects on Mental Health:
- Altered mood, including euphoria or irritability
- Impaired judgment and decision-making
- Changes in perception and sensory experiences
- Increased anxiety or paranoia
- Impulsiveness or risky behavior
Long-Term Effects on Mental Health:
- Cognitive impairments, such as memory loss and reduced concentration
- Increased risk of mental health disorders like depression and anxiety
- Dependence or addiction, leading to compulsive drug-seeking behavior
- Mood instability and emotional dysregulation
- Persistent psychosis or hallucinations in severe cases

What Drugs are Commonly Abused?

The drugs that are commonly abused are those that produce significant mind-altering effects, leading to dependency or addiction due to their impact on the brain’s reward system. Here is a list of commonly abused substances, each carrying specific risks and severity in terms of addiction and health effects:

Alcohol: Alcohol is a widely available and socially accepted substance, commonly abused for its relaxing and euphoric effects. Regular use leads to physical dependence, with severe withdrawal symptoms and risks of liver disease, heart problems, and mental health issues, making alcohol addiction challenging to overcome. 28.9 million people ages 12 and older (10.2% of this age group) had Alcohol Use Disorder (AUD) in the past year according to the 2023 National Survey on Drug Use and Health (NSDUH).
Nicotine: Nicotine, found in tobacco products, is highly addictive due to its rapid effect on brain dopamine levels. Nicotine addiction is severe, leading to long-term health consequences, such as cancer, respiratory issues, and cardiovascular disease. Among people aged 12 or older in 2021, 22.0% (or about 61.6 million people) reported using tobacco products or vaping nicotine in the past 30 days according to “What is the scope of tobacco, nicotine, and e-cigarette use in the United States?”published by the National Institute on Drug Abuse (NIDA).
Marijuana (Cannabis): Marijuana is commonly used for its relaxing and mind-altering effects, especially where it is legal or accessible. While less addictive than some other drugs, heavy marijuana use impairs memory, cognition, and mental health, leading to dependency in some users. In 2022, 30.7% of 12th graders reported using cannabis in the past year, and 6.3% reported using cannabis daily in the past 30 days according to “Cannabis and Teens” published by the Centers for Disease Control (CDC).
Heroin: Heroin, an illegal opioid, is highly addictive and produces intense euphoria. However, it quickly leads to severe physical dependence and painful withdrawal. Heroin addiction is among the most severe, with high risks of overdose and extensive health deterioration. In 2020, approximately 0.3% of individuals aged 12 or older reported using heroin in the past year, equating to about 902,000 people according to the “2020 National Survey on Drug Use and Health (NSDUH) Releases” published bySAMHSA.
Cocaine: Cocaine is a powerful stimulant commonly abused for its intense, short-term effects. Cocaine addiction leads to severe health problems, including heart issues, mental health disorders, and an increased risk of overdose. In 2020, about 1.9% of individuals aged 12 or older, or approximately 5.2 million people, reported using cocaine in the past year according to SAMHSA
Methamphetamine: Methamphetamine is a potent stimulant known for its intense euphoria and energy-boosting effects. Meth addiction is extremely severe, with lasting impacts on brain function, memory, and physical health, including significant dental and skin deterioration. In 2020, around 0.9% of individuals aged 12 or older, totaling about 2.6 million people, reported using methamphetamine in the past year according to the National Survey on Drug Use and Health.
Prescription Stimulants (e.g., Adderall, Ritalin): Prescription stimulants are misused for cognitive enhancement or energy boosts, particularly among students. Misuse of these stimulants leads to addiction, anxiety, cardiovascular problems, and cognitive decline. In 2021, approximately 1.3% of individuals aged 12 or older in the United States, equating to about 3.7 million people, reported misusing prescription stimulants in the past year according to Misuse of Prescription Drugs Research Report published by National Institute of Drug Abuse.
Benzodiazepines (e.g., Xanax, Valium): Benzodiazepines are prescribed for anxiety or sleep disorders but are highly addictive when misused. Benzodiazepine addiction is severe, with dangerous withdrawal symptoms and a risk of respiratory depression, especially when combined with other depressants. In 2020, about 4.8 million individuals aged 12 or older reported misusing benzodiazepines in the past year according to Key Substance Use and Mental Health Indicators in the United States:Results from the 2019 National Survey on Drug Use and Health.
MDMA (Ecstasy or Molly): MDMA is commonly abused for its empathogenic effects, especially in social and recreational settings. While not as physically addictive as some other drugs, frequent MDMA use leads to psychological dependence, dehydration, overheating, and long-term serotonin depletion. Among people aged 12 or older in the United States, 0.8% (or approximately 2.2 million people) reported using ecstasy in the past year according to “Ecstasy Statistics – National Data Of MDMA Abuse & Addiction” published by the Substance Abuse and Mental Health Services Administration.
Hallucinogens (e.g., LSD, Psilocybin): Hallucinogens are used for altering perception and producing visual or auditory hallucinations, in social or spiritual contexts. While generally not physically addictive, frequent use of hallucinogens leads to psychological dependence and, in some cases, persistent perceptual changes. 1.0% of adults 18+ used LSD in the past according to the 2021 National Survey on Drug Use and Health (NSDUH).
Fentanyl: Fentanyl is a potent synthetic opioid, one of the most dangerous drugs due to its extreme potency and high overdose risk. Mixed with other drugs unknowingly, fentanyl addiction is highly severe, leading to rapid dependence and frequent overdose fatalities. In 2022, 73,654 people died from a fentanyl overdose in the US, more than double the amount of deaths from three years prior in 2019 according to the National Center for Health Statistics (NCHS) in the U.S. Centers for Disease Control and Prevention (CDC).

What are the Categories of Drugs?

The categories of drugs are organized based on their effects, purposes, and how they impact the body and mind. Drugs fall into broad groups such as alcohol, psychoactive drugs, pain medications, prescription drugs, illegal drugs, and over-the-counter medications. These groups are broken down further into specific categories, each addressing unique therapeutic or recreational uses and having distinct impacts. Approximately 138.5 million individuals aged 12 or older reported consuming alcohol in the past month, representing about 50% of this age group, according to the 2020 National Survey on Drug Use and Health (NSDUH)This shows that depressants are the most commonly used category of drugs in the United States.

The categories of drugs are detailed below:

Stimulants: Stimulants increase alertness and energy by stimulating the central nervous system. Examples include caffeine, amphetamines (Adderall), methamphetamine, and cocaine. These substances are highly addictive, particularly amphetamines, methamphetamine, and cocaine, which cause intense psychological dependence due to their impact on dopamine levels in the brain.
Depressants: Depressants slow down brain activity, reducing anxiety and inducing relaxation. Examples include alcohol, benzodiazepines (Xanax, Ativan), and barbiturates (phenobarbital). Depressants like benzodiazepines and alcohol are highly addictive, leading to physical dependence and severe withdrawal symptoms when discontinued.
Opioids: Opioids provide pain relief by binding to opioid receptors in the brain and body. Examples include morphine, heroin, oxycodone, hydrocodone, and fentanyl. Opioids are extremely addictive, creating both physical and psychological dependence, with heroin and fentanyl posing particularly high addiction risks due to their potency.
Hallucinogens: Hallucinogens alter perception, mood, and cognition, causing visual and auditory distortions. Examples include LSD, psilocybin (magic mushrooms), DMT, and mescaline. Hallucinogens generally have a low risk of physical addiction, but psychological dependence develops with repeated use, especially with substances like LSD and DMT.
Cannabinoids: Cannabinoids affect mood and perception by acting on the body’s endocannabinoid system. Examples include THC (found in marijuana), CBD, and synthetic cannabinoids (Spice, K2). THC causes moderate psychological dependence, particularly with heavy use, while synthetic cannabinoids carry a higher risk of addiction and adverse effects.
Inhalants: Inhalants are volatile substances inhaled for short-term effects similar to alcohol intoxication. Examples include glue, gasoline, paint thinners, and nitrous oxide. Inhalants are moderately to highly addictive, especially with frequent use, leading to psychological dependence due to their quick, intense effects.
Dissociatives: Dissociatives create feelings of detachment from reality by disrupting signals between the brain and body. Examples include ketamine, PCP, and dextromethorphan (DXM). Dissociatives like ketamine and PCP have a moderate risk of psychological addiction, with users seeking out the dissociative effects repeatedly.
Antidepressants: Antidepressants balance neurotransmitters in the brain to treat depression and anxiety disorders. Examples include SSRIs (Prozac, Zoloft), SNRIs, and tricyclic antidepressants. These medications are generally not addictive, though some individuals experience withdrawal symptoms with abrupt discontinuation.
Antipsychotics: Antipsychotics manage symptoms of severe mental illnesses like schizophrenia and bipolar disorder by altering brain chemicals. Examples include clozapine, risperidone, and olanzapine. Antipsychotics are not considered addictive, though physical dependence occurs with long-term use.
Sedatives: Sedatives are calming agents that reduce anxiety and induce sleep. Examples include benzodiazepines (Valium), barbiturates (phenobarbital), and non-benzodiazepine sleep aids (Ambien). Sedatives are highly addictive, especially benzodiazepines and barbiturates, leading to both physical and psychological dependence with prolonged use.
Anxiolytics: Anxiolytics reduce anxiety, commonly prescribed for anxiety disorders. Examples include diazepam, alprazolam, and buspirone. Benzodiazepine-based anxiolytics carry a high risk of both psychological and physical dependence, particularly when used long-term.
Hypnotics: Hypnotics induce and maintain sleep, prescribed for insomnia. Examples include zolpidem (Ambien), eszopiclone (Lunesta), and certain benzodiazepines. Hypnotics, especially those in the benzodiazepine class, are highly addictive, with physical dependence and withdrawal symptoms common among users.
Antibiotics: Antibiotics treat bacterial infections by killing bacteria or inhibiting their growth. Examples include amoxicillin, ciprofloxacin, and doxycycline. Antibiotics have no addictive properties, although improper use leads to antibiotic resistance.
Antifungals: Antifungals treat fungal infections by killing fungi or stopping their growth. Examples include fluconazole, clotrimazole, and terbinafine. Antifungals do not have addictive properties and are generally safe for prescribed use.
Antivirals: Antivirals treat viral infections by preventing viruses from replicating. Examples include acyclovir (for herpes), oseltamivir (Tamiflu for influenza), and remdesivir (COVID-19). Antivirals are non-addictive and are not associated with dependency.
Anticonvulsants: Anticonvulsants prevent or control seizures by stabilizing electrical activity in the brain. Examples include carbamazepine, valproate, and gabapentin. Most anticonvulsants have low addiction risk, though gabapentin has a moderate risk of misuse and dependency.
Hormones: Hormones regulate bodily functions and are prescribed for hormone deficiencies or imbalances. Examples include insulin, estrogen, testosterone, and thyroid hormones. Hormones are not addictive, though dependency occurs when the body relies on hormone therapy for regulation.
Immunosuppressants: Immunosuppressants reduce immune response, used to prevent organ rejection in transplant patients. Examples include cyclosporine, azathioprine, and tacrolimus. These drugs have no addictive properties, although they require careful use to balance effectiveness and immune suppression.
Chemotherapy Agents: Chemotherapy agents kill or inhibit the growth of cancer cells. Examples include doxorubicin, cisplatin, and methotrexate. Chemotherapy agents are non-addictive and have no potential for dependency.
Anti-inflammatory Drugs: Anti-inflammatory drugs reduce inflammation and pain, prescribed for conditions like arthritis. Examples include ibuprofen, naproxen, and corticosteroids like prednisone. Most anti-inflammatory drugs, such as NSAIDs, have low addiction risk, though corticosteroids lead to dependency with long-term use.

What is Drug Abuse?

Drug abuse is the excessive or inappropriate use of substances that alter the mind or body, typically leading to harm to one’s health, behavior, or relationships. While drug abuse involves using a substance in a way that’s dangerous or excessive, addiction is a chronic disease characterized by an inability to stop using a drug despite harmful consequences.

Physical and psychological dependence on the substance develops, making it difficult to function without it. In 2022, 48.7 million people aged 12 or older (or 17.3% of the population) had a substance use disorder (SUD) in the past year according to the 2022 National Survey on Drug Use and Health (NSDUH) released by the Substance Abuse and Mental Health Services Administration (SAMHSA).

How Are Drugs Made?

Drugs are made through various processes that transform raw materials into finished products, involving chemical synthesis, extraction, or biological methods. Each method depends on the type of drug and its intended use.

The methods of how drugs are made are detailed below:

Chemical Synthesis: Chemical synthesis combines specific chemicals in controlled reactions to create drugs like antibiotics (e.g., ciprofloxacin) or stimulants (e.g., amphetamines). Chemists manipulate molecular structures step-by-step to ensure purity and stability, allowing for large-scale production of high-quality drugs.
Natural Extraction: Drugs like morphine and cannabis-based medications are derived from plants through natural extraction techniques, such as solvent extraction and distillation. After isolating the active compound, it’s purified to produce a concentrated form suitable for medical use.
Fermentation: Fermentation relies on microorganisms like bacteria or fungi to produce drugs as metabolic byproducts. For instance, penicillin, an antibiotic, is produced by fermenting the Penicillium mold in a bioreactor, where optimal conditions support high drug yields. The product is then purified and processed for distribution.
Biotechnology: Biotechnology uses genetically engineered organisms, such as bacteria or yeast, to produce drugs like insulin and erythropoietin. By introducing human genes, these cells are programmed to create specific proteins, which are harvested and purified for use in treating diabetes or anemia.
Formulation: After the active ingredient is prepared, it’s mixed with other components and processed into final forms, like tablets (e.g., acetaminophen), injectables (e.g., insulin), or inhalers (e.g., albuterol). Formulation ensures stability, dosage accuracy, and targeted delivery for effective treatment.

What are the Risks of Taking Drugs?

The risks of taking drugs are extensive, with three main risk factors including addiction, health complications, and impaired mental and physical functioning. Addiction is a significant risk, as many drugs alter brain chemistry, leading to dependency and compulsion to use. Health complications are also common, with risks like organ damage, weakened immune function, and increased vulnerability to diseases and even death. Over 100,000 people died from drug overdoses in the United States in 2021, with synthetic opioids like fentanyl accounting for the majority of these deaths according to “Overdose Deaths Involving Synthetic Opioids” published by the National Institute on Drug Abuse (NIDA) in 2022. Lastly, drug use impairs cognitive and motor skills, leading to poor decision-making, accidents, and in some cases, long-term mental health issues.

What is the Difference Between Legal and Illegal Drugs?

The difference between legal and illegal drugs is primarily in their status under the law. Legal drugs, such as alcohol, caffeine, and prescribed medications, are regulated and approved for use, for medical or recreational purposes, within certain limits. Illegal drugs, including substances like heroin, cocaine, and methamphetamine, are banned by law due to their high potential for abuse, severe health risks, and lack of accepted medical use. Legal drugs also become illegal when used without proper authorization or prescription.

What are Designer Drugs?

Designer drugs are synthetic substances chemically altered to mimic the effects of other drugs to evade legal restrictions. These drugs are created in laboratories and include examples like synthetic cannabinoids (e.g., Spice or K2, AK- 47, Cloud 9), synthetic stimulants (e.g., bath salts, MDMA, adderall), and synthetic opioids (e.g., fentanyl analogs, methadone, tramadol). Designer drugs pose high risks because their composition and potency varies greatly, leading to unpredictable and potentially dangerous effects. Among high school seniors, the annual prevalence of synthetic cannabinoid (a type of designer drug) consumption was reported at 8.0% in 2021 according to “Monitoring the Future Survey: High School Seniors’ Drug Use” published by the National Institute on Drug Abuse (NIDA).

What is Recreational Drug Use?

Recreational drug use is the intentional use of substances for pleasure or enjoyment rather than for medical purposes. To use drugs recreationally means consuming substances, such as alcohol, marijuana, or certain stimulants, to alter mood or experience relaxation, excitement, or euphoria. Recreational use occurs in social settings and leads to misuse or dependency if boundaries are not maintained.

Recreational drug use includes using substances to achieve pleasurable effects, which involves experimenting with or regularly using drugs like alcohol, marijuana, or other psychoactive substances in non-medical settings according to the National Institute on Drug Abuse in 2020.

How are Drugs Controlled?

Drugs are controlled by government agencies that regulate their manufacture, distribution, and use to protect public health and safety. In the United States, the Drug Enforcement Administration (DEA) and the Food and Drug Administration (FDA) classify drugs based on their medical use, safety, and potential for abuse, placing them into schedules that range from highly restricted (Schedule I) to less restricted (Schedule V). These regulations help manage access to dangerous drugs, enforce prescription requirements, and prevent illegal distribution.

How are Drugs Classified?

Drugs are classified by their effects, chemical composition, and abuse potential, under guidelines from the DEA and FDA. Functionally, they include stimulants (e.g., amphetamines, cocaine,meth ), depressants (e.g., benzodiazepines, alcohol, barbiturates), and opioids (e.g., morphine, heroin, oxycontin). Legally, drugs are placed into schedules:

Schedule I: Drugs with no accepted medical use and a high potential for abuse, including heroin, LSD, ecstasy, and peyote. These substances are illegal under federal law.
Schedule II: Drugs with accepted medical uses but high abuse potential, such as cocaine, methamphetamine, oxycodone, fentanyl, and Adderall. These drugs are tightly regulated and require a prescription.
Schedule III: Drugs with moderate to low potential for physical and psychological dependence, including ketamine, anabolic steroids, and certain formulations of codeine. They are available by prescription with restrictions.
Schedule IV: Drugs with a lower abuse potential, including benzodiazepines like Xanax, Valium, and sleep aids like Ambien. These drugs are commonly prescribed but still regulated.
Schedule V: Drugs with the lowest potential for abuse are available over the counter in limited quantities, such as cough preparations with small amounts of codeine and anti-diarrheal medications like Lomotil.

Can Drug Rehab Cure Drug Addiction?

Yes, drug rehab is effective in helping individuals manage and recover from addiction, although it is not necessarily a “cure” in a conventional sense due to the chronic nature of addiction. Treatment significantly reduces drug use and associated criminal activity, and improves social functioning. For instance, studies have shown that participation in comprehensive treatment programs can decrease drug use by 40% to 60% according to the National Institute on Drug Abuse (NIDA),. Drug rehab provides the tools for recovery, including therapies that address the underlying psychological causes of addiction, structured environments that reduce exposure to triggers, and aftercare support to reinforce long-term sobriety. These elements collectively empower individuals to rebuild healthy lifestyles and maintain long-term recovery.

What are Drugs that are Used for Treatment?

The drugs used for addiction treatment are medications that manage withdrawal symptoms, reduce cravings, or block the effects of addictive substances. Examples include:

Methadone: Methadone reduces cravings and withdrawal symptoms by activating opioid receptors without producing the full high.It is primarily used to treat opioid addiction.
Buprenorphine: Buprenorphine is a partial opioid agonist that helps manage opioid dependency by easing withdrawal symptoms and reducing cravings. It is commonly used in opioid addiction treatment.
Naltrexone: Naltrexone blocks opioid receptors, preventing the effects of opioids and also reducing cravings in alcohol addiction treatment. It is used for both opioid and alcohol addiction.
Disulfiram (Antabuse): Disulfiram causes unpleasant reactions when alcohol is consumed, such as nausea and flushing, which help discourage drinking. It is used specifically in the treatment of alcohol addiction.
Acamprosate: Acamprosate stabilizes brain chemistry to reduce cravings for alcohol in individuals recovering from alcohol dependence, supporting long-term abstinence.

Hope Without Commitment

Find the best treatment options. Call our free and confidential helpline

(800) 913-1755

Most private insurances accepted

Who Answers

How Do Drugs Function?

Drugs function by interacting with the body’s cells and influencing biological processes, through specific mechanisms. Approximately 45% of all therapeutic drugs exert their effects by binding to specific receptors on cell surfaces, thereby modulating cellular activity according to a study titled “Mechanisms of Drug Action: Receptors and Pharmacodynamics” by Rang et al., published in Pharmacology (2012). This interaction shows the importance of receptor-targeted therapies in modern medicine.

Drugs function by:

Receptor Binding: Many drugs work by binding to specific receptors on cell surfaces or within cells. These receptors are proteins that drugs activate or block to produce desired effects. For example, opioids bind to opioid receptors in the brain, reducing pain and producing a sense of euphoria by altering neurotransmitter activity.
Neurotransmitter Modulation: Some drugs affect the levels of neurotransmitters, which are chemical messengers in the brain. They enhance or inhibit the release, reuptake, or breakdown of neurotransmitters, impacting mood, pain perception, and other physiological responses. For instance, antidepressants like SSRIs increase serotonin availability by blocking its reuptake.
Enzyme Interaction: Certain drugs inhibit or enhance enzyme activity, affecting metabolic processes. For example, ACE inhibitors lower blood pressure by inhibiting an enzyme that constricts blood vessels, allowing for improved blood flow.
Ion Channel Modulation: Some drugs work by affecting ion channels, which control the flow of ions across cell membranes, influencing nerve and muscle function. Benzodiazepines, for instance, enhance the effect of GABA, an inhibitory neurotransmitter, by opening ion channels that reduce neuron excitability, leading to a calming effect.
Targeting Cell Structure or Function: Antibiotics, for instance, disrupt the cell walls or protein synthesis of bacteria, ultimately killing the bacteria without affecting human cells.

What are the Types of Organisms that Drugs Affect?

The types of organisms that drugs affect include humans, animals, bacteria, viruses, and fungi. Drugs are developed specifically for each type of organism, targeting their unique biological structures or processes to produce the desired therapeutic effect.

Humans: Most pharmaceuticals are designed for human use, addressing conditions like pain, infections, mental health disorders, and chronic diseases. Human drugs undergo rigorous testing for safety and efficacy.
Animals: Veterinary drugs are formulated specifically for animals, considering species-specific metabolism and physiology. These drugs treat conditions in pets, livestock, and wildlife, including infections, pain, and behavioral issues.
Bacteria: Antibiotics target bacteria by disrupting essential functions like cell wall synthesis or protein production, killing the bacteria or preventing their growth. These drugs are carefully developed to avoid affecting human cells.
Viruses: Antiviral drugs inhibit virus replication within host cells, aiming to reduce viral load and symptoms in infected organisms. They are designed to interfere with viral processes without damaging host cells.
Fungi: Antifungal drugs treat fungal infections by targeting structures unique to fungi, such as the fungal cell membrane. These drugs are essential for treating skin infections and invasive fungal infections.

What are the Beneficial Effects of Drugs?

The beneficial effects of drugs are extensive, providing relief from symptoms, treating diseases, and improving quality of life. Drugs manage pain, reduce inflammation, treat infections, and stabilize mental health conditions. For example, antibiotics cure bacterial infections, while insulin regulates blood sugar in diabetes, preventing serious complications. Vaccines prevent diseases by building immunity, and antihypertensives manage high blood pressure, reducing stroke and heart attack risk. A meta-analysis published in The Lancet in 2018 evaluated 21 antidepressant drugs and found that all were more effective than placebo in treating major depressive disorder, with odds ratios ranging from 1.37 to 2.13. This indicates that patients receiving these medications were up to twice as likely to experience symptom improvement compared to those receiving a placebo.These treatments (anti-depressants, antibiotics, pain relievers) enable individuals to live healthier, more productive lives.

What are the Harmful Effects of Drugs?

The harmful effects of drugs are significant, especially when misused or taken long-term, leading to side effects, dependency, and chronic health issues. Common risks include liver damage from excessive alcohol use, lung damage from smoking, and increased heart rate from stimulant abuse. Opioids, for instance, effectively relieve pain but carry a high risk of addiction, respiratory depression, and overdose when misused. Benzodiazepines, used for anxiety, causes dependence and cognitive impairment with prolonged use. Even prescription drugs, if taken incorrectly, will cause serious adverse effects. The most harmful effect is overdose which occurs with most types of drugs if taken in high doses. In 2022, there were an estimated 107,941 drug overdose deaths in the United States according to “Drug Overdose Deaths: Facts and Figures” published by National Institute on Drug Abuse (NIDA) in 2024.

What is Drug Treatment?

Drug treatment is the use of medications or therapies to manage, cure, or prevent diseases. Drug treatment aims to improve health outcomes, alleviate symptoms, and restore functioning. Treatment options include medications like antibiotics to treat infections, antihypertensives to manage blood pressure, and mental health therapies to address psychological conditions. Treatments are selected based on the patient’s condition, age, medical history, and specific health goals, ensuring a personalized approach to optimize effectiveness and safety.

What are the Principles of Drug Action?

The principles of drug action are based on four key processes: absorption, distribution, metabolism, and excretion according to Dhillon S, Kostrzewski AJ study titled Pharmacokinetics by StatPearls. Absorption refers to how a drug enters the bloodstream through oral ingestion, injection, or topical application. Distribution describes how the drug moves through the body to reach its target tissues or organs. Metabolism involves the body’s breakdown of the drug, primarily in the liver, to make it easier to eliminate. Excretion is the removal of the drug from the body, typically via the kidneys. These processes collectively determine a drug’s therapeutic effects (desired outcomes) versus its toxic effects (potential harm), balancing efficacy with safety.

What are the Target Molecules that Drugs Interact With?

The target molecules that drugs interact with are specific structures in the body that influence how drugs produce their effects. By binding to these targets, drugs either activate or inhibit biological processes to achieve therapeutic outcomes. Key target molecules include:

Receptors: Proteins on cell surfaces or within cells that drugs bind to in order to activate or block specific cellular responses. Receptors are primary targets in treatments for conditions like pain, anxiety, and hypertension.
Enzymes: Proteins that catalyze biochemical reactions; drugs inhibit enzymes to prevent specific reactions, such as reducing inflammation or lowering blood pressure.
Ion Channels: Pathways that control the flow of ions across cell membranes, affecting nerve and muscle activity. Drugs that modulate ion channels reduce symptoms like pain or seizures.
Transport Proteins: Proteins that move substances across cell membranes; some drugs inhibit these to alter neurotransmitter levels, which is common in antidepressant treatments.

Each of these targets allows drugs to modify biological processes in a way that supports health and manages symptoms.

What is the Drug Dose-Response Relationship?

The drug dose-response relationship is the correlation between the dose of a drug and its effect on the body. As the dose increases, the drug’s effect typically intensifies up to a point, after which additional dosing does not increase the effect and could lead to toxicity. This relationship is central to determining a drug’s potency (the dose needed for effect) and efficacy (the maximum effect achievable). Understanding the dose-response relationship is crucial in treatment planning to ensure the dose is high enough to be effective but low enough to avoid adverse effects, balancing therapeutic benefits with safety.

What is a Median Effective Drug Dose?

The median effective drug dose, or ED50, is the dose at which a drug produces a therapeutic effect in 50% of the population according to Median effective dose by National Center for Advancing Translational Sciences (NCATS). This measure helps determine a drug’s therapeutic effectiveness and guides dosing for safe, effective treatment. ED50 is a critical parameter in drug development and clinical practice, as it indicates the optimal starting dose to achieve desired effects in most patients without excessive risk, allowing for adjustments based on individual response.

What Factors Affect Drug Variability?

The factors that affect drug variability are gender, age, weight, diet and interactions with other drugs. These influence how a drug’s effects and side effects manifest in each person. Variability factors impact how the body absorbs, metabolizes, and responds to medications.

Gender: Gender differences are a large factor based on size and chemical makeup of men vs. women. A review of clinical data from 300 new drug applications submitted to the FDA between 1994 and 2000 found that 31% of studies showed significant sex-based differences in how drugs are processed in the body, with over 20% differences in pharmacokinetics (PK) between men and women. In this review, 11 drugs showed more than a 40% difference in PK measures between sexes, yet no dosing adjustments based on sex were recommended.
Age: Older adults metabolize drugs more slowly, while children require adjusted doses due to developmental factors. A study by D. Turnheim, titled “When drug therapy gets old: pharmacokinetics and pharmacodynamics in the elderly,” published in Experimental Gerontology in 2003, highlights that renal clearance of drugs decrease by approximately 1% per year after the age of 40. This decline necessitates careful dose adjustments in older adults to maintain therapeutic efficacy and minimize adverse effects.
Weight: Body weight influences drug distribution, with larger doses are required for higher body weights. A study titled “The Relationship between Drug Clearance and Body Size” published in Clinical Pharmacokinetics found that drug clearance rates vary by up to 50% between individuals of different body weights, even when adjusted for body surface area.
Diet: Certain foods or nutrients enhance or inhibit drug absorption, impacting effectiveness. Poor diet or not eating before taking certain drugs or medications will significantly affect absorption.
Interactions with Other Drugs: Concurrent medications affect drug action, increasing the risk of adverse effects or reducing therapeutic benefits. a study by Dresser et al., titled “The effect of cytochrome P450 3A inhibition on the pharmacokinetics of domperidone,” published in Clinical Pharmacology & Therapeutics (2000), demonstrated that co-administration of ketoconazole, a potent CYP3A4 inhibitor, increased the area under the curve (AUC) of domperidone by approximately 3-fold. This interaction shows the importance of monitoring and adjusting dosages when multiple medications are prescribed concurrently to avoid adverse effects or reduced therapeutic efficacy.

What are the Adverse Effects of Drugs?

The adverse effects of drugs are varied (cognitive impairment, toxicity, allergic reactions) based on the drug. These unintended and potentially harmful reactions that occur during treatment include but are not limited to:

Allergic Reactions: Allergic reactions occur when the immune system misidentifies a drug as harmful, triggering responses ranging from skin rashes and itching to severe swelling (angioedema) and life-threatening anaphylaxis. Common triggers include antibiotics like penicillin, specific painkillers, and contrast dyes in imaging procedures. Managing these reactions involves discontinuing the drug and, in severe cases, administering emergency treatments like epinephrine.
Toxicity: Toxicity arises when drug concentrations in the body reach harmful levels due to overdose, accumulation, or interactions with other drugs, leading to organ damage in the liver (hepatotoxicity), kidneys (nephrotoxicity), or heart. For instance, acetaminophen overdose results in severe liver toxicity, while excessive ibuprofen use leads to kidney damage. Monitoring blood levels and adhering to prescribed dosages prevent toxicity according to “Drug-Induced Liver Injury” by Reuben et al., New England Journal of Medicine, 2016.
Dependence: Dependence occurs as the body adapts to a drug, resulting in physical or psychological reliance. Stopping the drug brings withdrawal symptoms, including anxiety, cravings, tremors, and seizures in severe cases. Opioids, benzodiazepines, and some antidepressants frequently lead to dependence, which develops even under medical supervision with prolonged use. Dependence is distinct from addiction, as it involves physical adaptation rather than compulsive misuse.
Gastrointestinal Distress: Drugs that irritate the digestive tract cause nausea, vomiting, diarrhea, and stomach cramps. NSAIDs like ibuprofen irritate the stomach lining, and antibiotics disrupt gut flora, leading to symptoms managed by taking the drug with food, adjusting dosages, or prescribing acid-reducing medications.
Cognitive Impairment: Drugs affecting the central nervous system cause cognitive impairment, impacting memory, concentration, and mental clarity. Sedatives, antidepressants, and antihistamines cause drowsiness, confusion, and slowed thinking, affecting daily activities. Long-term use of certain medications, particularly in older adults, exacerbates these effects according to “The Cognitive Impact of Anticholinergic Drugs” by Campbell et al., Journal of the American Geriatrics Society, 2009.
Organ Damage: Long-term or high-dose use of specific medications leads to cumulative damage to vital organs. Chronic NSAID use harms the kidneys, while extended statin therapy strains the liver. Chemotherapy drugs, though life-saving, result in heart or lung damage over time. Monitoring and regular adjustments in treatment minimize long-term harm according to “Long-term Effects of Statins on Liver Function” by Kashani et al., Hepatology, 2011.

How are Drugs Absorbed in the Organism?

Drugs are absorbed into the organism through various pathways that transport them from the site of administration to the bloodstream. Common absorption pathways include oral ingestion, where drugs are absorbed through the digestive tract; injection, delivering drugs directly into the bloodstream, muscles, or tissues for rapid onset; and inhalation, where drugs are absorbed through the lungs for fast effects. Absorption rates influence the onset (how quickly the drug takes effect) and bioavailability (the amount of drug reaching the bloodstream). For example, orally ingested drugs have lower bioavailability due to breakdown in the digestive system, while intravenous injections have almost complete bioavailability as they bypass digestive barriers.

How are Drugs Distributed in the Organism?

Drugs are distributed in the organism by moving through the bloodstream to reach tissues and organs. This distribution process is influenced by blood flow to different areas, tissue binding (how drugs attach to proteins within tissues), and selective barriers like the blood-brain barrier, which limits certain drugs from entering the brain. Highly vascularized tissues, like the liver and kidneys, receive drugs quickly, whereas other areas, such as fat tissue, receive drugs more slowly. Distribution determines the concentration of the drug in different tissues, affecting both therapeutic effects and potential side effects.

How are Drugs Metabolized by the Human Organism?

Drugs are metabolized by the human organism primarily in the liver, where enzymes break down drugs into metabolites that are easier for the body to eliminate. This metabolic process involves cytochrome P450 enzymes, which modify drugs chemically, sometimes activating or deactivating their effects. Metabolism affects both the duration of drug action and its potency; for example, a drug metabolized quickly by the liver requires frequent dosing. Certain populations have slower or faster metabolisms due to genetic or environmental factors, impacting drug effects according to “Role of Cytochrome P450 in Drug Metabolism” by Guengerich, Pharmacology & Therapeutics, 2008.

How are Drugs Eliminated by the Human Organism?

Drugs are eliminated by the human organism through various pathways (renal, biliary, pulmonary excretion and saliva/sweat), primarily involving the kidneys and the excretory system. This process is crucial for determining appropriate drug dosing and frequency to avoid accumulation and toxicity.

Renal Excretion: The kidneys filter out drugs and their metabolites, which are then excreted through urine.
Biliary Excretion: The liver secretes some drug metabolites into bile, which is then excreted in the feces.
Pulmonary Excretion: Certain drugs, especially those administered by inhalation, are eliminated through the lungs during exhalation.
Sweat and Saliva: Minor amounts of drugs are excreted through sweat and saliva, although this route is not typically significant for dosing purposes.

The elimination process ensures that drugs do not build up to toxic levels in the body, supporting safe and effective treatment outcomes.

How are Drugs in Medicine Classified?

Drugs in medicine are classified by their purpose and mechanism of action, which helps healthcare professionals select appropriate treatments based on a drug’s effects. By purpose, drugs are grouped based on what they treat, such as analgesics (pain relievers), antibiotics (bacteria-targeting agents), antivirals (for viral infections), antidepressants (mood stabilizers for mental health), and antihypertensives (for lowering blood pressure). By action, drugs are categorized based on their physiological effects, such as stimulants (increase alertness), depressants (reduce nervous system activity), antipsychotics (manage severe mental disorders), and hallucinogens (alter perception). Classification allows for organized prescribing and helps ensure that drugs are used safely and effectively for specific health conditions.

What is Pharmacology?

Pharmacology is the study of drug action on biological systems, encompassing how drugs interact with body processes to produce therapeutic effects according to “What Is Pharmacology?” published by the University of Alberta. This field is divided into branches like pharmacodynamics (how drugs affect the body) and pharmacokinetics (how the body processes drugs). Pharmacology is vital to medicine because it guides the development of new drugs, informs safe dosing, and helps predict interactions, enhancing patient care and outcomes.

What is the History of Drugs?

The history of drugs is deeply intertwined with human civilization, dating back to ancient times when early societies utilized natural substances for healing, ritual, and recreational purposes. Archaeological findings suggest that as early as the Neolithic Period (12,000 – 2,000 B.C.E.), people in regions like Mesopotamia and South America turned to plant-based substances for medicinal and spiritual uses. Archaeologist Elisa Guerra-Doce from the University of Valladolid in Spain highlights evidence from prehistoric burials, suggesting psychoactive plant use was both medicinal and ritualistic, embedding drug use into societal healing according to “Prehistoric Drugs: Hallucinogenic Plant Use in Ritual Contexts,” by Journal of Archaeological Science in 2015.

During the medieval period, drugs evolved with the development of herbal medicine across different cultures. In Europe, herbs like mandrake and henbane were used for sedation and pain relief, while in China, traditional medicine was taking shape, using hundreds of herbs to balance the body’s energy. The Silk Road facilitated the exchange of these medicinal plants, spreading pharmacological knowledge across continents. According to Ahmed Ragab, a historian of science at Harvard University, the Islamic Golden Age played a significant role in refining extraction techniques, laying the groundwork for pharmacology according to “Medieval Islamic Medicine,” by Oxford University Press in 2012, and demonstrating an early understanding of chemical interactions.

The 19th century marked a turning point with the isolation of specific compounds, such as morphine from opium, which allowed for precise dosing. This era saw the birth of modern pharmacology, and soon afterward, the discovery of synthetic drugs like aspirin in 1897 by Felix Hoffmann revolutionized pain management. As described in Jonathan Ott’s “Pharmacotheon: Entheogenic Drugs, Their Plant Sources, and History” published by Natural Products Co., 1996, this period exposed societies to the addictive potential of these compounds, particularly opiates, prompting the first calls for regulation.

In the 20th century, drug development accelerated with discoveries such as Alexander Fleming’s penicillin in 1928, which transformed the treatment of bacterial infections and drastically reduced mortality rates according to “The Discovery of Penicillin,” The British Medical Journal, 2005). The establishment of the U.S. Food and Drug Administration (FDA) in 1906 set a global precedent for regulating drug safety, as explained by Philip J. Hilts in Protecting America’s Health: The FDA, Business, and One Hundred Years of Regulation in 2003. The pharmaceutical boom of this century introduced new drugs targeting mental health, heart disease, and other chronic conditions, fundamentally shaping the field of medicine.

Today, drug development is at the forefront of biotechnology and personalized medicine, with advances in pharmacogenomics allowing for more tailored treatments. Dr. Francis Collins, former director of the National Institutes of Health (NIH), highlights the promise of genetic insights in drug development, emphasizing their potential to maximize efficacy and minimize side effects according to Collins, “The Language of Life: DNA and the Revolution in Personalized Medicine,” HarperCollins, 2010. The history of drugs, from ancient practices to cutting-edge innovations, reflects an evolving journey that continues to shape the future of health and medicine.

Find Drug Rehabilitation Centers Near You Anywhere In the US

Addiction Resource team has compiled an extensive list of the top drug rehabilitation facilities around the country. Click on the state you are interested in, and you'll get a list of the best centers in the area, along with their levels of care, working hours, and contact information. Haven't found the rehab you need? Call the toll-free helpline below for professional assistance.

Published on: September 25th, 2015

Updated on: January 20th, 2025

What are Drugs: Definition, Usage, Effects and Types

What is the Definition of a Drug?

Why Do People Use Drugs?

What are the Methods of Taking Drugs?