Liver Extraction Ratio Quiz
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Questions and Answers

What does the liver extraction ratio (ER) measure?

  • General distribution of the drug in the body
  • Drug concentration in the liver
  • Blood flow to the liver
  • Drug removal from the liver after oral administration (correct)

    • What does an ER of 0.25 indicate?

  • 100% of the drug is removed by the liver
  • 75% of the drug is removed by the liver
  • 25% of the drug is removed by the liver (correct)
  • 50% of the drug is removed by the liver

    • How is hepatic clearance (Clh) calculated if both the ER and the blood flow to the liver are known?

  • Clh=Q-ER
  • Clh=Q×Ca-Cv/Ca
  • Clh=Ca/Cv
  • Clh=Q×ER (correct)

    • Why is sampling of drug from the hepatic portal vein and artery difficult?

    <p>It requires invasive procedures in humans</p> Signup and view all the answers

    Why may animal ER values be quite different from those in humans?

    <p>There are variations in drug metabolism between animals and humans</p> Signup and view all the answers

    Which factor(s) affect the hepatic clearance of a drug?

    <p>All of the above</p> Signup and view all the answers

    What is the relationship between bioavailability (F), liver extraction (ER), and fraction of drug removed by nonhepatic process (F″)?

    <p>$F = 1 - ER - F″$</p> Signup and view all the answers

    For drugs with very high extraction ratios, how does the rate of drug metabolism respond to changes in hepatic blood flow?

    <p>The rate of drug metabolism increases with increased hepatic blood flow</p> Signup and view all the answers

    What is used to describe the total ability of the liver to metabolize a drug in the absence of flow limitations?

    <p>Intrinsic clearance</p> Signup and view all the answers

    What can increase the intrinsic clearance for the metabolism of many drugs?

    <p>Smoking</p> Signup and view all the answers

    What does a liver extraction ratio (ER) value of 0.25 indicate?

    <p>75% of the drug is removed by the liver</p> Signup and view all the answers

    How is hepatic clearance (Clh) calculated when both the liver extraction ratio (ER) and the blood flow to the liver are known?

    <p>$Clh = Q \times ER$</p> Signup and view all the answers

    What factor(s) affect the hepatic clearance of a drug?

    <p>Blood flow to the liver and drug concentration in blood</p> Signup and view all the answers

    Why may animal ER values be quite different from those in humans?

    <p>Variability in hepatic blood flow between animals and humans</p> Signup and view all the answers

    What does the liver extraction ratio (ER) provide a direct measurement of?

    <p>Drug removal from the liver after oral administration</p> Signup and view all the answers

    In the context of hepatic clearance, what is the significance of intrinsic clearance (Clint)?

    <p>It reflects the inherent ability of the liver to metabolize a drug, unaffected by blood flow.</p> Signup and view all the answers

    What characterizes drugs with high extraction ratios in terms of hepatic clearance?

    <p>Their clearance is sensitive to changes in hepatic blood flow.</p> Signup and view all the answers

    What factor primarily affects drugs with low extraction ratios in terms of hepatic clearance?

    <p>Changes in intrinsic activity of mixed-function oxidases.</p> Signup and view all the answers

    How does propranolol, a beta-adrenergic blocking agent, affect its own hepatic clearance when given orally?

    <p>It decreases hepatic blood flow, resulting in slower clearance.</p> Signup and view all the answers

    What condition can increase the intrinsic clearance for the metabolism of many drugs?

    <p>Smoking</p> Signup and view all the answers

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