A drug is administered orally and its absolute bioavailability is calculated to be 25%. If the same dose is given intravenously, which statement is correct?
- A The AUC after IV administration will be 4 times the oral AUC ✓
- B The drug undergoes less first-pass metabolism
- C The AUC after oral administration will be 4 times the IV AUC
- D The volume of distribution is reduced
Correct answer: A. The AUC after IV administration will be 4 times the oral AUC
Explanation
Absolute bioavailability is the fraction of the drug that reaches systemic circulation, calculated as the ratio of the area under the curve (AUC) of an extravascular route to the AUC of intravenous administration. If oral bioavailability is 25%, the oral AUC is one-fourth of the IV AUC, making the IV AUC four times higher than the oral AUC. Option C incorrectly reverses this ratio, while option D is unrelated to bioavailability.
Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.
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