BIOAVAILABILITY

Define bioavailability

The fraction of an administered dose that reaches systemic circulation unchanged

What does bioavailability measure

Rate and extent of drug absorption

What is Cmax

The maximum plasma concentration achieved after drug administration

What is Tmax

The time at which Cmax occurs

What does Cmax indicate

Extent of absorption and sometimes rate of absorption

What does Tmax indicate

Rate of absorption (shorter Tmax = faster absorption)

What does AUC represent

Total drug exposure over time; extent of absorption

How to compare bioavailability of two formulations

Compare their AUCs; higher AUC = greater extent of absorption

Relative bioavailability definition

Bioavailability of a dosage form compared to another dosage form of the same drug

Absolute bioavailability definition

Bioavailability of a dosage form compared to IV administration (IV = 100%)

How to determine relative bioavailability

Compare the AUC of test formulation to reference formulation

How to determine absolute bioavailability

Compare AUC of oral (or other route) to AUC of IV

Define bioequivalence

Two drug formulations show no significant difference in rate and extent of absorption

How to know if two products are bioequivalent

Their Cmax, Tmax, and AUC fall within accepted limits (80–125%)

Why bioequivalence matters

Ensures therapeutic equivalence for generics and brand products