A drug is any substance that causes a change in an organism's physiology or psychology when consumed.[3][4] Drugs are typically distinguished from food and substances that provide nutritional support.Consumption of drugs can be via inhalation, injection, smoking, ingestion, absorption via a patch on the skin, or dissolution under the tongue.In pharmacology, a drug is a chemical substance, typically of known structure, which, when administered to a living organism, produces a biological effect. A pharmaceutical drug, also called a medication or medicine, is a chemical substance used to treat, cure, prevent, or diagnose a disease or to promote well-being.[3] Traditionally drugs were obtained through extraction from medicinal plants, but more recently also by organic synthesis.[6] Pharmaceutical drugs may be used for a limited duration, or on a regular basis for chronic disorders