Which term describes the movement of a substance from the site of administration into the bloodstream?

• A. Absorption
• B. Distribution
• C. Metabolism
• D. Excretion

Answer: (A)

Absorption is the movement of a drug from its site of administration into the bloodstream. It determines how much of the dose reaches systemic circulation and how quickly it starts acting. After absorption, the drug may be distributed to tissues, metabolized (chemically altered, mainly in the liver), or excreted (eliminated from the body). The other processes describe what happens after the drug enters the bloodstream: distribution moves it from blood to organs, metabolism changes its chemical form, and excretion removes it from the body.