Absorption involves which elements?

• A. The route of administration and bioavailability
• B. The distribution of a drug to tissues
• C. The route of administration, bioavailability, and the amount of medication that passes through absorbing surfaces
• D. The metabolism of a drug

Answer: (B)

Absorption is the process by which a drug moves from its site of administration into the bloodstream. The elements that define this process include the route of administration (how the drug is given, which affects the barriers it faces), the bioavailability (the portion of the dose that actually reaches systemic circulation), and the amount of medication that passes through absorbing surfaces (how much is taken up at the site of entry). These factors together determine how much drug enters the circulation and how quickly it happens. Distribution, by contrast, describes how the drug then moves from the bloodstream into tissues, not how it enters the blood, and metabolism refers to chemical changes the drug undergoes, mainly in the liver. So the best description of absorption is that it involves the route of administration, bioavailability, and the amount absorbed through absorbing surfaces.