Intrinsic clearance Clint is defined as the organ’s inherent ability to clear drug independent of blood flow.

• A. Clint is the liver’s inherent ability to clear drug independent of blood flow.
• B. Clint equals CLh when fu = 1.
• C. Clint is the product of hepatic blood flow and unbound fraction.
• D. Clint has no relevance to hepatic clearance.

Answer: (A)

Intrinsic clearance reflects the liver’s enzymatic capacity to remove a drug without regard to how much blood is delivering the drug. This is exactly what Clint measures—the organ’s inherent ability to clear a drug, independent of blood flow. In vivo hepatic clearance, CLh, depends on both this intrinsic capacity and hepatic blood flow (Qh), linked by the well-known relationship CLh = (Qh × Clint) / (Qh + Clint). This shows Clint as the capacity term that, together with flow, determines how quickly the liver clears the drug. It’s not simply the product of flow and unbound fraction, and Clint remains relevant to hepatic clearance; the equality to CLh only occurs under specific, simplifying conditions, not as a general rule.