A 70-year-old woman requires a drug that undergoes extensive first-pass metabolism in the liver. Compared to a 30-year-old adult at the same oral dose, which pharmacokinetic change is MOST likely in the elderly patient?
- A Increased renal clearance due to glomerular hyperfiltration
- B Increased bioavailability due to reduced hepatic blood flow ✓
- C Faster absorption due to increased gastric motility
- D Reduced volume of distribution due to increased total body water
Correct answer: B. Increased bioavailability due to reduced hepatic blood flow
Explanation
Hepatic blood flow decreases by approximately 40% with ageing, reducing first-pass extraction of high-extraction drugs such as propranolol, lidocaine, and morphine, paradoxically increasing their oral bioavailability and plasma concentrations. Renal clearance declines with age, not increases. Gastric motility slows in the elderly. Total body water decreases with age, causing water-soluble drugs to have a smaller, not larger, Vd.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.