What does bioavailability mean?

• A. The portion of a drug that reaches systemic circulation and can have an effect.
• B. The expiration status of a drug in the market.
• C. The stability of a drug in solution.
• D. The color, odor, taste attributes of a drug.

Answer: (A)

Bioavailability is the fraction of an administered drug that reaches the bloodstream in an active form and can produce an effect. It shows how much of the dose actually becomes available to tissues after absorption and any metabolism. For intravenous administration, bioavailability is essentially 100% because the drug goes directly into circulation. For other routes, like oral, it’s usually less due to incomplete absorption and first-pass metabolism. This idea is different from shelf life (expiration status), chemical stability in a solution, or taste and smell attributes of the drug.