Drug

A drug is any substance other than food that when inhaled injected smoked consumed absorbed via a patch on the skin or dissolved under the tongue causes a physiological change in the body.

In the pharmacology pharmaceutical drug or medicine is a chemical substance used to treat cure prevent diagnose a disease or promote well being traditionally drugs were obtained through extraction from medicinal plants but more recently also by organic synthesis pharmaceutical drugs may be used for a limited duration or on a regular basis for chronic disorders.

Pharmaceutical drugs are often classified into drug classes groups of related drugs that have similar chemical structures the same mechanism of action a related mode of action and that are used to teat the same disease.

The Anatomical therapeutic chemical classification system ATC the most widely used drug classification system assigns drugs a unique ATC code which is an alphanumeric code that assigns it to specific drug classes within the ATC system another major classification system is the Biopharmaceutics Classification system this classifies drugs according to their solubility and permeability or absorption properties.