What is "mechanism of action"

mechanism of action \mech"an*ism of ac"tion\, n. (Medicine, Biochemistry) The mechanism[2] by which a pharmacologically active substance produces an effect on a living organism or in a biochemical system; as, the mechanism of action of actinomycin involves its binding to DNA. The mechanism of action is usually considered to include an identification of the specific molecular targets to which a pharmacologically active substance binds or whose biochemical action it influences; a general recognition of the broad biochemical pathways (such as DNA synthesis, protein synthesis, cholesterol synthesis) which are inhibited or affected by a substance is termed its mode of action.

In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. A mechanism of action usually includes mention of the specific molecular targets to which the drug binds, such as an enzyme or receptor. Receptor sites have specific affinities for drugs based on the chemical structure of the drug, as well as the specific action that occurs there. Drugs that do not bind to receptors produce their corresponding therapeutic effect by simply interacting with chemical or physical properties in the body. Common examples of drugs that work in this way are antacids and laxatives.

In comparison, a mode of action (MoA) describes functional or anatomical changes, at the cellular level, resulting from the exposure of a living organism to a substance.