mechanism of action

The mechanism of action is the story of exactly how a drug produces its effect, told at the molecular level. It is the answer to the question 'what does the drug actually grab, and what happens next?' rather than just 'what does the drug do for the patient.'

Precisely, it is the specific biochemical interaction through which a drug produces its pharmacological effect. For example, a drug might bind an enzyme's active site and block it, or attach to a receptor and switch it on, setting off a chain of downstream events that leads to the observed benefit.

Understanding the mechanism helps predict side effects, design better follow-up molecules, and explain why a drug works in some patients but not others. Notably, some clinically useful drugs were discovered before their mechanism was understood, and a few still have mechanisms that are only partly worked out.