In a bioequivalence study, a new oral tablet formulation of a drug is compared with the reference product. Which measurement provides the primary estimate of the extent of absorption?
- A Peak plasma concentration (Cmax)
- B Time to reach peak concentration (Tmax)
- C Area under the plasma concentration-time curve (AUC) ✓
- D Apparent volume of distribution (Vd)
Correct answer: C. Area under the plasma concentration-time curve (AUC)
Explanation
Bioavailability is calculated as the ratio of the AUC after extravascular administration to the AUC after intravenous administration, corrected for dose if they differ. AUC integrates total systemic exposure and therefore reflects the extent of absorption. Cmax and Tmax reflect the rate of absorption, not the extent, and a formulation can show an adequate AUC yet fail bioequivalence because of a different absorption rate. Volume of distribution is irrelevant to absorption and is not derived from these curves alone.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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