The hepatic extraction ratio of lidocaine is 0.7 (high). Lidocaine is given orally to a patient. Its bioavailability will be approximately:

• A 70%
• B 50%
• C 90%
• D 30% ✓

Explanation

Bioavailability after oral administration for a high extraction ratio drug = 1 − Extraction Ratio = 1 − 0.7 = 0.3 = 30%. High extraction ratio drugs undergo extensive first-pass metabolism in the liver; approximately 70% is metabolized on the first pass through the portal circulation. This is why lidocaine, despite near-complete GI absorption, has only ~30% oral bioavailability and must be given parenterally (IV or IM) to achieve therapeutic plasma concentrations. Propranolol (ER ~0.6), morphine, and verapamil are similar examples.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.