Which statement is true about bioavailability?

Which statement is true about bioavailability?

• A. The fraction of an administered dose that reaches systemic circulation
• B. The rate at which a drug is metabolized
• C. The time to onset of action
• D. The amount of drug excreted unchanged

Answer: (A)

Bioavailability refers to the fraction of an administered dose that actually reaches the bloodstream in active form. This is what makes the statement true: it specifically measures how much of the drug becomes available systemically after any route of administration, accounting for absorption and any loss to first-pass metabolism. For an intravenous dose, bioavailability is 100% because the drug goes directly into systemic circulation. The rate at which a drug is metabolized describes metabolism, not how much gets into circulation. The time to onset of action depends on how quickly the drug is absorbed and acts, which is about speed rather than the extent of absorption. The amount excreted unchanged relates to elimination, not how much reaches the bloodstream.

Bioavailability refers to the fraction of an administered dose that actually reaches the bloodstream in active form. This is what makes the statement true: it specifically measures how much of the drug becomes available systemically after any route of administration, accounting for absorption and any loss to first-pass metabolism. For an intravenous dose, bioavailability is 100% because the drug goes directly into systemic circulation. The rate at which a drug is metabolized describes metabolism, not how much gets into circulation. The time to onset of action depends on how quickly the drug is absorbed and acts, which is about speed rather than the extent of absorption. The amount excreted unchanged relates to elimination, not how much reaches the bloodstream.