Mechanism 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.

There are many drugs in which the mechanism of action is known. By knowing the interaction between a certain site of a drug and a receptor, other drugs can be formulated in a way that replicates this interaction, thus producing the same therapeutic effects. Indeed, this method is used to create new drugs.

The mechanism of action of aspirin involves irreversible inhibition of the enzyme cyclooxygenase; therefore suppressing the production of prostaglandins and thromboxanes, thus reducing pain and inflammation. This mechanism of action is specific to aspirin, and is not constant for all nonsteroidal anti-inflammatory drugs (NSAIDs). Rather, aspirin is the only NSAID that irreversibly inhibits COX-1.

Some drug mechanisms of action are still unknown. However, even though the mechanism of action of a certain drug is unknown, the drug still functions; it is just unknown or unclear how the drug interacts with receptors and produces its therapeutic effect.

In some literature articles, the term mechanism of action and mode of action (MoA) are used interchangeably; typically referring to the way in which the drug interacts and produces a medical effect. However, in actuality, a mode of action describes functional or anatomical changes, at the cellular level, resulting from the exposure of a living organism to a substance. This differs from a mechanism of action, as it is a more specific term that focuses on the interaction between the drug itself and an enzyme or receptor and its particular form of interaction, whether through inhibition, activation, agonism, or antagonism. Furthermore, the term mechanism of action is the main term that is primarily used in pharmacology, whereas mode of action will more often appear in the field of microbiology or certain aspects of biology.

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