Pharmacology is the branch of medicine and biology concerned with the study of drug action,where a drug can be broadly defined as any man-made, natural,or endogenous (within the body) molecules which expert a biochemical and/or physiological effect on the cell,tissue,organ , or organism (sometime the word pharmacon is used as a term to encompass these endogenous and exogenous bioactive species). More specifically, it is the study of the interactions biochemical function. If substances have medicinal properties, they are considered pharmaceuticals.

Pharmacology explores the mechanisms that drugs use to cause therapeutic effects. The basic principle of pharmacology is that therapeutic agents are effective because they mimic or block molecules that regulate natural processes like blood pressure, organ development, and pain perception.