Step 1: What is bioequivalence? Bioequivalence means a generic drug delivers the same amount of active ingredient to the blood at the same rate as the brand-name drug, under similar conditions. It ensures therapeutic equivalence without repeating full clinical trials.
Step 2: The FDA standard. The US FDA requires that the 90% confidence interval (CI) for the ratio of the test product to the reference product must fall within 80.00–125.00% for both AUC (total exposure) and Cmax (peak concentration).
Step 3: Why AUC and Cmax? AUC reflects the total amount of drug absorbed (extent of absorption). Cmax reflects the peak level reached in blood (rate of absorption). Both together ensure the generic product is neither under-absorbed nor over-absorbed.
Step 4: Why not the other options? 50–150% is too wide a range and not used. 90–110% is too narrow and is only used for narrow therapeutic index drugs in some contexts. 70–130% for half-life is not an FDA bioequivalence criterion.
Step 5: Conclusion. The FDA bioequivalence criterion is 80–125% CI for both AUC and Cmax. This is a regulatory standard all pharmacy students must know.
Answer: Option (3) — 80–125% confidence interval for AUC and C max