Describe the well-stirred hepatic clearance model and identify its key variables.

Unlock all questions

This demo includes only 20 questions. Upgrade to access hundreds of questions, flashcards, exam simulations, and disable ads.

Full question bankExam simulationsFlashcards
From $24.99Unlock all

Study for the Pharmaceutics Drug Disposition Test. Prepare with flashcards and multiple choice questions, each answer has hints and explanations. Get set for your exam!

Multiple Choice

Describe the well-stirred hepatic clearance model and identify its key variables.

Explanation:
This model shows how the liver clears a drug by combining how fast blood comes through the liver with how capable the liver enzymes are at metabolizing the drug, while only the unbound fraction of the drug can be cleared. The well-stirred expression for hepatic clearance is CLh = Qh × (fup × CLint) / (Qh + fup × CLint). Here, CLint is the intrinsic clearance reflecting liver enzyme capacity, fup is the fraction unbound in plasma (only unbound drug can be metabolized), and Qh is hepatic blood flow. This form captures both flow-limited and capacity-limited behavior: if fup × CLint is much smaller than Qh, clearance approaches fup × CLint (metabolism-limited by intrinsic capacity); if fup × CLint is much larger than Qh, clearance approaches Qh (flow-limited by delivery). The given expression correctly places fup × CLint in both the numerator and the denominator, which yields the appropriate limiting cases and units. The other forms omit fup × CLint in the right places or omit fup entirely, which misrepresents how delivery and metabolic capacity balance to determine hepatic clearance.

This model shows how the liver clears a drug by combining how fast blood comes through the liver with how capable the liver enzymes are at metabolizing the drug, while only the unbound fraction of the drug can be cleared. The well-stirred expression for hepatic clearance is CLh = Qh × (fup × CLint) / (Qh + fup × CLint). Here, CLint is the intrinsic clearance reflecting liver enzyme capacity, fup is the fraction unbound in plasma (only unbound drug can be metabolized), and Qh is hepatic blood flow. This form captures both flow-limited and capacity-limited behavior: if fup × CLint is much smaller than Qh, clearance approaches fup × CLint (metabolism-limited by intrinsic capacity); if fup × CLint is much larger than Qh, clearance approaches Qh (flow-limited by delivery). The given expression correctly places fup × CLint in both the numerator and the denominator, which yields the appropriate limiting cases and units. The other forms omit fup × CLint in the right places or omit fup entirely, which misrepresents how delivery and metabolic capacity balance to determine hepatic clearance.

More Multiple Choice Questions
Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy