The function of a drug or the particular action of a drug on an organism is called:

• A. Pharmacokinetics
• B. Mechanism of Action
• C. Therapeutic index
• D. Adverse effect

Answer: (B)

Understanding the mechanism of action explains how a drug exerts its effect in the body. It describes the specific target or process the drug interacts with—such as binding to a receptor, inhibiting an enzyme, or altering ion channels—that leads to the therapeutic outcome. This is different from pharmacokinetics, which deals with how the body handles the drug (absorption, distribution, metabolism, excretion). It also differs from the therapeutic index, which relates to safety margins, and from adverse effects, which are unwanted responses. For example, a drug that blocks a receptor to lower blood pressure works through its mechanism of action.