What does drug bioavailability measure?

Question

Bioavailability is:

Answer choices

1. The amount of drug reaching the systemic circulation relative to the administered dose.
2. The amount of drug eliminated.
3. The amount of unbound drug in plasma.

Explanation

Bioavailability indicates the fraction of an administered dose that reaches the systemic circulation unchanged. It is expressed as a fraction or a percentage.

It differs from the amount eliminated and from the unbound fraction in plasma. Losses during absorption and presystemic elimination can reduce bioavailability.