High ER Flow-Dependent Clearance — FRCA Primary MCQ

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HardPharmacology - General PrinciplesHigh ER Flow-Dependent ClearanceFRCA Primary

A drug with an extraction ratio of 0.9 has its clearance primarily determined by:

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Correct answer: D — Hepatic blood flow

High extraction ratio drugs (>0.7) have flow-dependent clearance. Changes in hepatic blood flow directly alter clearance. Changes in protein binding or enzyme activity have minimal effect because the liver extracts almost all drug presented to it. Examples: propofol / lidocaine / propranolol / morphine / pethidine.

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care