Drug
Overview
A drug (藥物, drug) is a chemical or biological substance that, when administered to a living body, alters physiological function and is used for the diagnosis, treatment, prevention, and alleviation of disease. In modern medicine, drugs are counted along with surgery and radiotherapy as one of the three major therapeutic means, and pharmacology (약리학) is the discipline that scientifically studies the components, mechanisms of action, movement within the body, and clinical effects of drugs. At the same time, drugs carry the social risks of dependence, tolerance, addiction, and misuse, making them a dual-natured subject that requires both legal regulation and ethical management.
Main Content
Definition and Classification of Drugs
Drugs are broadly divided into pharmaceuticals (prescription drugs and over-the-counter drugs) and non-pharmaceuticals (narcotics, psychotropic substances, inhalants, etc.). By mode of action they are classified into central nervous system agents, cardiovascular drugs, antibiotics, antivirals, hormones, anticancer drugs, and the like, and by origin into naturally derived substances, synthetic compounds, and biopharmaceuticals (antibodies, vaccines, gene therapies). In South Korea, the Pharmaceutical Affairs Act (약사법) and the Act on the Control of Narcotics, Etc. (마약류 관리에 관한 법률) govern pharmaceuticals and narcotics, respectively.
Pharmacokinetics and Pharmacological Action
Pharmacokinetics, which deals with how a drug moves within the body, is summarized by the four stages of Absorption, Distribution, Metabolism, and Excretion — the so-called ADME. Oral administration passes through the hepatic portal vein and is subject to the first-pass effect, whereas intravenous administration has a bioavailability close to 100 percent. Drugs act by binding to target proteins such as receptors, enzymes, ion channels, and transporters, and the dose-response curve, which expresses the relationship between concentration and effect, forms the basis for determining clinical doses.
Prescription and Medication Management
A prescription is determined by combining the diagnosis, indication, dosage, route of administration, duration of administration, and contraindications. In the elderly, pregnant women, children, and patients with reduced renal or hepatic function, drug-metabolizing capacity differs, making dose adjustment essential. Medication adherence is a factor that determines the success or failure of treatment, and keeping to dosing times, not stopping arbitrarily, and safely disposing of leftover drugs are important. Even if symptoms improve, antibiotics must be taken for the full prescribed duration in order to reduce resistance.
Adverse Reactions and Interactions
All drugs carry the possibility of adverse reactions along with their effects. Typical examples include gastrointestinal disturbance, hepatotoxicity, nephrotoxicity, allergic reactions, and anaphylaxis, and drug-drug interactions change blood concentrations unpredictably through inhibition or induction of metabolic enzymes (the CYP450 family). The combination of warfarin with certain antibiotics, and of grapefruit juice with statin-class drugs, are representative examples.
Misuse, Tolerance, and Dependence
Narcotics and psychotropic substances are necessary for the treatment of pain and mental illness, but repeated use can cause tolerance, dependence, and withdrawal syndrome. Addiction is not merely a matter of willpower but a disease explained by neurological changes in the brain's reward circuit, and it requires a continuous approach of prevention, early detection, treatment, and rehabilitation. The spread of synthetic drugs such as fentanyl and methamphetamine is treated as an international public health threat.
Recent Trends
The biggest current in the drug field in 2024–2025 is the explosive growth of treatments for obesity and metabolic diseases. The GLP-1 receptor agonist class (semaglutide, tirzepatide, etc.) has shown effects in obesity, reduction of cardiovascular risk, and some liver diseases, reshaping the market and clinical guidelines, and the development of oral formulations and multi-action agents is active. In addition, the approval and expanded use of antibody therapeutics for Alzheimer's disease and the commercialization of gene-editing-based therapeutics have gained full momentum.
Artificial intelligence is changing the entire drug development process. Using protein structure prediction and generative models, candidate substances are derived within months, and cases of applying AI to clinical trial patient selection and failure prediction have increased. In 2025, cases were reported of substances to whose design AI contributed entering the clinical stage, and discussions on evaluation guidelines by regulatory authorities are also under way.
On the institutional side, alongside strengthened narcotics control, expanding access to medical narcotics and the clinical and regulatory review of psychedelic-class therapeutics (psilocybin, MDMA) are major issues. Responding to antibiotic resistance (AMR) is leading to country-by-country prescription management and incentives for new antibiotics, and digital therapeutics and wearable-based monitoring of drug response are also being introduced into clinical practice.
In South Korea, surveys on the actual state of narcotics misuse, preventive education for adolescents, and the overhaul of the collection system for unused and expired medicines have been strengthened, and crackdowns on blocking illegal online sales and on the distribution of prescription-only drugs without a prescription are expanding.
Related Topics
- [[Pharmacology]]
- [[Narcotics]]
- [[Antibiotic Resistance]]
- [[Vaccine]]
- [[Clinical Trial]]
- [[Drug Development]]
- [[Pharmaceutical Affairs Act]]