Drugs: Definition, Usage, Types, Effects

Drugs serve multiple purposes depending on their type, dosage, and context. Many are essential therapeutic tools for treating diseases, managing symptoms, and improving quality of life. Others are used recreationally or may pose risks when misused

According to the World Health Organization (WHO), “a drug is any substance that, when taken into the body, alters its function either physically or psychologically, excluding food and water.”

This means drugs can heal, prevent, or manage disease—but also harm, depending on dosage, legality, and context of use.

A complementary concept is medicine, which is a subset of drugs specifically designed, tested, and regulated for safe therapeutic purposes.

Drugs are used by physicians, pharmacists, patients, and recreational users—these groups are collectively called drug consumers or drug users, though their intentions and outcomes differ widely.

The primary uses of drugs include medical treatment, recreational enjoyment, performance enhancement, and self-medication. Medically, drugs treat diseases, manage pain, and improve mental health. Recreational drugs are used for pleasure and relaxation but carry risks.

The modern scientific classification of drugs began in the 19th century, with the rise of pharmacology, and expanded rapidly after the Controlled Substances Act of 1970 in the United States.

The types of drugs include: Prescription Drugs, Over-the-Counter Drugs, Recreational Drugs, Illicit Drugs, and Traditional/Herbal Substances.

Certain drug types are addictive, and users can develop a chronic condition that alters brain chemistry, leading to compulsive drug use despite, as studied by the National Institute for Drug Abuse (NIDA), “Understanding Drug Use and Addiction DrugFacts.” Prescription medications, illicit substances, and even legal drugs cause addiction.

What Are Drugs?

Drugs are substances that, when introduced into the body, alter its functions either physically or mentally. They are used for medical purposes, such as treating illnesses and managing pain, or for recreational use, leading to mind-altering effects. Some drugs are legal and regulated, like prescription medications and over-the-counter treatments, while others are illegal due to their potential for abuse and harm.

Drugs are classified based on their legal status, effects on the body, and potential for addiction. Legally, drugs are either approved for medical use or banned due to their high risk of misuse. Prescription drugs require a doctor’s approval, while over-the-counter drugs are purchased freely. Illegal drugs, such as heroin and cocaine, are prohibited due to their dangerous effects. 

Based on their effects, drugs are categorized as stimulants, depressants, hallucinogens, and opioids. Stimulants, like cocaine and amphetamines, increase alertness and energy. Depressants, such as alcohol and benzodiazepines, slow down brain activity, leading to relaxation. Hallucinogens, including LSD and magic mushrooms, alter perception and mood. Opioids, like morphine and heroin, are powerful pain relievers that also carry a high risk of addiction.

According to the National Center for Drug Abuse Statistics (NCDAS), in 2020, 13.5% of Americans aged 12 and older used drugs, reflecting a 3.8% year-over-year increase. Over one year, 21.4% (59.3 million people) either used illegal drugs or misused prescription medications. Lifetime drug use among this age group stands at 50%, affecting approximately 138.5 million people.

How Are Drugs Made?

Drugs are made through chemical synthesis, extraction from natural sources, or biotechnology-based processes. Pharmaceutical drugs are developed in laboratories through precise chemical reactions, ensuring purity and effectiveness.

Natural drugs, like morphine or cocaine, are derived from plants through extraction and refinement. Advances in biotechnology allow for the creation of complex drugs, such as insulin, using genetically modified organisms.

Once a drug is formulated, it undergoes rigorous testing, clinical trials, and regulatory approval before reaching consumers.

The drugs are made using the following methods:

• Chemical Synthesis: Many pharmaceutical drugs are created through controlled chemical reactions in laboratories. Scientists design specific molecular structures to achieve the desired therapeutic effects, ensuring stability and consistency in production.
• Extraction from Natural Sources: Some drugs originate from plants, fungi, or microorganisms. Active compounds are extracted, purified, and processed into medications. Examples include morphine from opium poppies and penicillin from mold.
• Biotechnological Methods: Advanced drugs, such as insulin and vaccines, are produced using genetically modified bacteria, yeast, or cells. These organisms are engineered to produce specific proteins or compounds necessary for medical treatments.
• Fermentation: Certain drugs, like antibiotics and some antidepressants, are produced through microbial fermentation. This process involves growing bacteria or fungi to generate bioactive compounds under controlled conditions.
• Semi-Synthetic Modification: Some drugs begin as natural compounds but are chemically altered to enhance their effectiveness or reduce side effects. An example is heroin, which is derived from morphine but modified to have different properties.

How Do People Take Drugs?  

People take drugs through oral consumption, inhalation, injection, topical application, and sublingual or buccal absorption. The intake method affects how quickly and intensely the drug acts on the body. Some methods produce rapid effects, while others provide a slower, sustained release.

People take drugs in the following ways:

• Oral Consumption: Oral consumption is the most common method, where drugs are swallowed in the form of pills, capsules, or liquids. The drug is absorbed through the digestive system and enters the bloodstream, but the effects take longer to appear due to metabolism in the liver.
• Inhalation: Drugs like nicotine, cannabis, or certain anesthetics are inhaled as smoke, vapor, or aerosol. This method allows substances to enter the bloodstream quickly through the lungs, producing almost immediate effects.
• Injection: Drugs are injected directly into a vein (intravenous), muscle (intramuscular), or under the skin (subcutaneous). Injection provides rapid and potent effects, making it a common method for medical treatments as well as illicit drug use, particularly with substances like heroin. According to a study by Bradley H, Hall EW, Asher A, et al. 2023, titled “Estimated Number of People Who Inject Drugs in the United States,” an estimated 3.69 million people in the United States injected drugs, accounting for 1.46% of the adult population.
• Topical Application: Some drugs are applied to the skin as creams, gels, or patches. These substances are absorbed slowly into the bloodstream or act locally on the skin, as seen with pain relief creams or nicotine patches.
• Sublingual/Buccal Absorption: Certain drugs dissolve under the tongue (sublingual) or between the cheek and gum (buccal). This allows rapid absorption into the bloodstream without passing through the digestive system, leading to faster effects than oral ingestion.

The method of drug intake significantly impacts its onset and intensity. Inhalation and intravenous injection lead to immediate and intense effects. Oral and topical methods usually have slower absorption rates, leading to prolonged but less intense effects. 

What Are the Uses of Drugs?

Drugs are used for various reasons, ranging from medical treatment to recreational and social influences. Medically, prescription drugs help manage conditions like pain, infections, or mental health disorders.

Some individuals use drugs recreationally for relaxation or euphoria, while others seek performance enhancement in sports or academics. Self-medication is another common reason why people use drugs to cope with stress, anxiety, or physical discomfort.

Curiosity, peer pressure, and cultural or religious practices also drive drug use. According to the National Institute on Drug Abuse (NIDA), substance use begins for social or experimental reasons but leads to dependency in some cases.

People use drugs for the following reasons:

• Medical treatment: Prescription medications help treat illnesses, manage pain, or regulate mental health conditions.
• Recreational use: Some substances are used for pleasure, relaxation, or altering perception.
• Performance enhancement: Drugs like stimulants or steroids are used to boost athletic, academic, or work performance.
• Self-medication: Individuals use substances to manage anxiety, stress, or chronic pain without medical supervision.
• Curiosity and experimentation: Many people, especially young adults, try drugs out of curiosity.
• Peer pressure: Social influences play a role in substance use, particularly among adolescents.
• Cultural or religious practices: Some societies use specific substances in rituals, ceremonies, or spiritual practices.

What Are the Side Effects of Drugs?

The common side effects of drugs are highlighted below:

• Nausea and vomiting: Occurs with antibiotics, opioids, NSAIDs, antidepressants, and chemotherapy drugs due to stomach irritation or stimulation of the brain’s nausea centers. Often managed by taking medication with food or using antiemetics. Many patients develop tolerance within days to weeks.
• Upset stomach and indigestion: Common with NSAIDs, antibiotics, and iron supplements. Managed with food intake, enteric-coated formulations, or alternative medications.
• Diarrhea or constipation: Antibiotics disrupt gut bacteria, leading to diarrhea; opioids slow intestinal motility, resulting in constipation. Managed with probiotics, stool softeners, adequate hydration, or dietary adjustments.
• Changes in appetite: Some medications increase appetite (corticosteroids, certain antidepressants), others decrease it (stimulants, some antibiotics). Usually temporary and resolves with dosage stabilization.
• Drowsiness and sedation: Common with antihistamines, muscle relaxants, anti-anxiety medications, and some pain relievers. Managed by taking at bedtime, avoiding driving during peak effects, or switching to non-sedating alternatives.
• Dizziness and lightheadedness: Frequent with blood pressure medications, diuretics, and anti-anxiety drugs, often from blood pressure changes when standing. Managed by rising slowly, adequate hydration, and dosage adjustments.
• Headache: Occurs with antibiotics, blood pressure medications, hormone therapies, and stimulants. Usually resolves within days to weeks as the body adjusts.
• Difficulty concentrating or mild cognitive changes: Temporary “brain fog” with sedatives, antihistamines, or certain blood pressure medications. Typically mild and reversible with dosage adjustments.
• Insomnia or sleep disturbances: Stimulants, some antidepressants, and corticosteroids can interfere with sleep patterns. Managed by taking medications early in the day and practicing good sleep hygiene.
• Changes in heart rate: Stimulants increase heart rate; beta-blockers slow it therapeutically. Managed through regular monitoring and dosage adjustments.
• Blood pressure fluctuations: Antihypertensives lower blood pressure (may cause initial dizziness); stimulants and NSAIDs can raise it. Managed with regular monitoring and gradual dosage titration.
• Palpitations: Sensation of rapid or strong heartbeats with stimulants, bronchodilators, or thyroid medications. Usually benign, but should be evaluated if persistent.

What is Drug Abuse? 

Drug abuse is the habitual or compulsive use of substances in a way that harms physical health, mental well-being, or daily functioning. It involves the misuse of legal or illegal drugs, leading to dependence, addiction, and severe social and health impacts. Many individuals engage in drug abuse due to factors like stress, peer pressure, or underlying mental health conditions.

What Are the Most Commonly Abused Drugs?  

The most commonly abused drugs are alcohol, nicotine, cannabis (marijuana), heroin, cocaine, methamphetamine, MDMA, hallucinogens, and fentanyl. These substances are widely misused due to their accessibility, addictive properties, and the temporary pleasurable effects they produce.

What Is the Difference Between Legal and Illegal Drugs?

The main difference between legal and illegal drugs is that legal drugs are approved for medical or recreational use under government regulations, while illegal drugs are prohibited due to their high potential for abuse and harm. Legal drugs, such as prescription medications, alcohol, and nicotine, are obtained lawfully but still lead to addiction if misused. Illegal drugs, including heroin, cocaine, and methamphetamine, are banned because they pose significant health and safety risks. Some substances, like marijuana, fall into a gray area, as their legality varies by state and country. The classification of drugs is based on their medical benefits, potential for misuse, and societal impact.