A drug is any substance that can be used to treat an illness, to relieve a symptom, to enhance performance or ability, to alter states of mind or to modify a chemical process or processes in the body. The word "drug" is etymologically derived from the Dutch/Low German word "droog", which means "dry", since in the past, most drugs were dried plant parts.
The term "drug" is necessarily a vague one, being defined by intent: for example, foods consumed for normal metabolism are not generally considered "drugs", but the same foods consumed for a more specific purpose (such as the use of alcohol as a depressant or caffeine as a stimulant) may be. Depending on the definition used, the same substance may even be considered both a food and a drug at the same time. The term "medication" is frequently applied to drugs used for medical treatment, presumably to avoid confusion with recreational drugs.
The effects of a particular drug can vary greatly depending on a number of factors:
Two patterns of distribution, licensed and illegal, are created by laws designed to prevent or punish perceived abuse or to protect the interests of licensed producers, suppliers and users. Laws may be designed also (not least with respect to alcohol and tobacco) to generate government tax revenue.
In the United States, medical professionals may obtain drugs from drug companies or pharmacies (which in turn purchase drugs from the drug companies). Pharmacies may also supply a drug directly to patients, authorized by a prescription from a medical professional, if the drug can be safely self-administered. Most drugs are relatively high-cost for patients to purchase directly when first distributed, although health insurance may mitigate some of the cost. When the patent for a drug runs out, a generic drug (some known as simply a "generic") is usually synthesized and released by competing companies, causing the price to drop markedly. Drugs which don't require prescription by a medical professional are known as over-the-counter (OTC) drugs and can be sold in stores without pharmacy association.
Many self-recreational drugs are illegal almost everywhere, meaning that their distribution is a criminal industry. This results in adulterated products such as soap bar. See Drug policy of the Netherlands.
Drugs may be classified in many different ways, according to mechanism of action, effects, or even legal status.
Usage of most of drugs is regulated to some extent. While details vary with location, these are somewhat usual regulations in the Western world:
Regulated to some extent (age or labeling requirements, for example) but available over the counter:
Prescription drugs, prohibited for non-medical use:
Varies from tolerated to prohibited for medical use:
Varies from prohibited for non-medical use to prohibited for any use
Prohibited for any use, no medical uses currently allowed
Three international UN treaties regulate drugs laws: