For fu = 0.9, CLint = 100 L/h, and Qh = 25 L/h, calculate CLh using the well-stirred hepatic clearance model and classify extraction as high or low.

• A. CLh ≈ 19.6 L/h; high extraction
• B. CLh ≈ 90 L/h; high extraction
• C. CLh ≈ 25 L/h; low extraction
• D. CLh ≈ 0.9 L/h; negligible extraction

Answer: (A)

The calculation uses the well-stirred hepatic clearance model: CLh = (Qh × fu × CLint) / (Qh + fu × CLint).

First find fu × CLint: 0.9 × 100 = 90 L/h. The numerator becomes Qh × fu × CLint = 25 × 90 = 2250. The denominator is Qh + fu × CLint = 25 + 90 = 115. So CLh = 2250 / 115 ≈ 19.6 L/h.

To classify extraction, use the extraction ratio E = CLh / Qh = 19.6 / 25 ≈ 0.78, which is high extraction.

Thus, the hepatic clearance is about 19.6 L/h with high extraction.