Drug Absorption · Pharmacology

Which of the following describes 'First-Pass Metabolism'?

  1. Excretion of the drug by the kidneys on the first circuit
  2. Metabolism of a drug in the gut wall or liver before it reaches systemic circulation
  3. Binding of a drug to plasma proteins immediately after absorption
  4. Distribution of the drug from blood into the brain across the protective blood-brain barrier
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Correct answer: Metabolism of a drug in the gut wall or liver before it reaches systemic circulation

Drugs absorbed from the GI tract enter the portal venous system and pass through the liver. Significant enzymatic degradation in the liver or gut wall reduces the amount of active drug that enters the general circulation.

Difficulty: Medium Question 4 of 20

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