Medicine

What this page covers

Medicine is too broad for one short page, so this overview follows how modern medicine tests treatments, approves and delivers medicines, and protects whole populations. MedlinePlus, the US National Library of Medicine’s health site, describes clinical trials as studies that look for better ways to prevent, screen for, diagnose or treat disease.^[6] The World Health Organization (WHO) calls a health system all the activities whose main purpose is to promote, restore or maintain health.^[14]

How medicines are tested

The NHS (UK) describes a clinical trial as a comparison of one treatment with another, in patients, healthy people or both.^[1] A new medicine is usually tested against a control: either a dummy treatment called a placebo, or a standard treatment already in use.^[1] The NHS says such trials move through a series of stages that check whether the medicine is safe and whether it works, from a small first group, sometimes healthy volunteers, to larger groups of people who are ill.^[1]

In most trials a computer randomly decides which group each patient joins, and many are blinded, so nobody knows who is getting which treatment, which helps reduce bias.^[1] In the UK, all medical research involving people must first be approved by an independent research ethics committee.^[1] In the US, many trials are overseen by an Institutional Review Board (IRB), which checks that a study is ethical and that its risks are reasonable next to its possible benefits.^[6]

How the US learned to regulate medicines

A history chapter published by the US Food and Drug Administration (FDA) tells how American drug law grew. It describes how, in 1937, a company sold a liquid form of the new drug sulfanilamide without testing it in animals or people, and its solvent was a poison.^[7] The disaster killed over 100 people, and Congress answered with the 1938 Food, Drug, and Cosmetic Act, which for the first time made new drugs pass a safety review before sale.^[7]

In 1961 thalidomide, a popular drug in Europe, was found to cause severe birth defects and deaths in babies when taken early in pregnancy; because FDA reviewer Dr Frances Kelsey had concerns, it was never approved for sale in the US.^[7] The 1962 Drug Amendments that followed required evidence that a new drug works, not only that it is safe.^[7] The chapter says the randomised, double-blind, placebo-controlled trial became the benchmark for judging other methods, often called the gold standard.^[7]

Licensing and safety in the UK

In the UK, licences for medicines are granted by the Medicines and Healthcare products Regulatory Agency (MHRA) after clinical trials.^[2] In England and Wales, the National Institute for Health and Care Excellence (NICE) then decides whether the NHS should provide a treatment.^[1] Checking continues after licensing, because rare side effects missed in trials may appear for the first time.^[1] People in the UK can report suspected side effects to the MHRA’s Yellow Card Scheme, and in rare cases a medicine may be withdrawn.^[2]

How medicines reach people

The NHS (UK) describes three routes: some medicines for minor illnesses can be bought over the counter, some are sold only under a pharmacist’s supervision, and prescription-only medicines such as antibiotics must be prescribed by a qualified health professional.^[2] A medicine’s generic name is the name of its active ingredient, while its brand name is chosen by the company that made it.^[2]

Worldwide, the WHO keeps a Model List of essential medicines, those that safely and effectively treat a population’s priority health needs; its 2025 edition includes over 520 medicines.^[15]

Screening, prevention and vaccines

The CDC (US) describes screening tests as medical tests that look for disease early, when it may be easier to treat.^[8] Vaccines teach the immune system to make antibodies that protect against a disease; the Immune System page explains how.^[4] The CDC (US) estimates that routine vaccinations of children born during 1994–2023 will have saved over 1.1 million lives.^[9]

Smallpox: a disease wiped out

The WHO says smallpox is still the only human disease ever eradicated.^[16] In 1796 the English doctor Edward Jenner used material from a cowpox sore to inoculate eight-year-old James Phipps, the first person vaccinated against smallpox.^{[10, 16]} According to the WHO, the World Health Assembly called for global eradication in 1958, and an intensified programme was launched in 1967.^[16] The World Health Assembly declared the world free of smallpox on 8 May 1980.^[10]

Antibiotics and resistance

The CDC’s history of penicillin tells how Alexander Fleming noticed a zone around a mould on a culture plate where bacteria did not grow, named its active agent penicillin, and published his findings in 1929.^[11] In 1945 Fleming, Chain and Florey were awarded the Nobel Prize for it.^[11]

The WHO defines antimicrobial resistance (AMR) as bacteria, viruses, fungi and parasites no longer responding to antimicrobial medicines, and says misuse and overuse of those medicines are driving it.^[17] It estimates that bacterial AMR was associated with more than 4.7 million deaths worldwide in 2021.^[17] The WHO also describes a research and development crisis, with few new antimicrobial medicines in the pipeline.^[17]

Health systems and health workers

The WHO defines universal health coverage (UHC) as all people being able to get the quality health services they need, when and where they need them, without financial hardship.^[18] It estimates that about 4.6 billion people were not fully covered in 2023.^[18] WHO data show that regions with the heaviest burden of disease have the fewest health workers, and that nurses are the largest single group of health workers in every region.^[19]

Common misconceptions

“Antibiotics cure colds.” The CDC (US) says antibiotics do not treat infections caused by viruses, such as colds, and that taking them when they are not needed will not help while their side effects can still cause harm.^[12]

“An approved medicine carries no risk.” The NHS (UK) says no medicine is completely risk free.^[2]

“Generic medicines are weaker copies.” The NHS (UK) says generic versions are the same as the branded medicine because they contain the same active ingredients.^[2]

“Smallpox was beaten by a cure.” The WHO says no cure was ever found; eradication came through prevention.^[16]

What this page does not cover

This overview does not describe medical specialties, surgery, how diagnosis works in practice or how drugs act in the body, and it gives no medical advice or doses. The NHS (UK) keeps separate guides to surgery and procedures, tests, screening and other treatments.^[5]

Going further

See Immune System for how vaccines train the body’s defences, Nutrition for food and health, Anatomy for the body’s structure, and Body & Health for the rest of this region.