Bioavailability of the drug is:
- a- Rate of absorption.
- b- Extent of absorption.***
- c- Rate & extent.
The correct answer is: b) Extent of absorption.
Bioavailability refers to the fraction of an administered drug that reaches the systemic circulation in an unchanged form and becomes available to its site of action. It is not concerned with the rate at which the drug is absorbed, but rather the total amount that makes it into circulation.
Here's why the other options are incorrect:
a) Rate of absorption:
While the rate of absorption is a factor that influences bioavailability, it is not the same thing. A drug could be absorbed very quickly but still have low bioavailability if it is poorly absorbed through the chosen route of administration or extensively metabolized before reaching the bloodstream.
c) Rate & extent:
This is the closest option, but it is redundant to mention both rate and extent within the context of bioavailability, as it already encompasses both aspects.
Therefore, the extent of absorption is the most accurate single answer to describe the meaning of bioavailability.
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pharmacology