What does the body do to a drug?

• A. Pharmacokinetics
• B. Pharmacodynamics
• C. Bioavailability
• D. Side effects

Answer: (A)

The main idea is how the body handles a drug, which is described by pharmacokinetics. This field covers the body's processing of the drug from entry to elimination: absorption into the bloodstream, distribution to tissues, metabolism (chemical changes), and excretion. Together, these steps determine how much drug reaches systemic circulation, how long it stays active, and how it’s cleared from the body.

Pharmacodynamics, in contrast, is about what the drug does to the body—its effects and mechanisms—rather than how the body processes the drug. Bioavailability is a specific aspect of pharmacokinetics, referring to the fraction of the administered dose that reaches circulation. Side effects are the observable reactions the body has to the drug, not the body's processing of it.

So, the body does to a drug is best described by pharmacokinetics.