What is total body clearance (CL) and how is it calculated after IV administration?

What is total body clearance (CL) and how is it calculated after IV administration?

• A. CL equals AUC / Dose; it is the volume of plasma cleared per unit time.
• B. CL equals Dose × AUC; it is the rate of drug elimination.
• C. CL equals Dose / AUC; it is the volume of plasma cleared per unit time.
• D. CL equals Cmax / AUC; it is the fraction cleared per hour.

Answer: (C)

Clearance is the volume of plasma from which the drug is completely removed per unit time. After IV administration, the entire dose enters the bloodstream, and the total exposure over time is captured by the AUC. For linear pharmacokinetics with IV dosing, the relationship is AUC = Dose / CL, so the clearance is CL = Dose / AUC. This means a larger AUC (more exposure) implies slower clearance, and a given dose is cleared more slowly if less plasma volume is effectively being cleared per unit time. The units line up as Dose (mg) divided by AUC (mg·h/L) giving CL in L/h. This option aligns with the fundamental definition and the IV, linear kinetics assumption. The other formulas don’t reflect how clearance connects dose, exposure, and time: Dose × AUC mixes units and represents something other than clearance; AUC/Dose would not yield a clearance value; and Cmax/AUC involves peak concentration rather than the overall elimination process.

Clearance is the volume of plasma from which the drug is completely removed per unit time. After IV administration, the entire dose enters the bloodstream, and the total exposure over time is captured by the AUC. For linear pharmacokinetics with IV dosing, the relationship is AUC = Dose / CL, so the clearance is CL = Dose / AUC. This means a larger AUC (more exposure) implies slower clearance, and a given dose is cleared more slowly if less plasma volume is effectively being cleared per unit time. The units line up as Dose (mg) divided by AUC (mg·h/L) giving CL in L/h. This option aligns with the fundamental definition and the IV, linear kinetics assumption. The other formulas don’t reflect how clearance connects dose, exposure, and time: Dose × AUC mixes units and represents something other than clearance; AUC/Dose would not yield a clearance value; and Cmax/AUC involves peak concentration rather than the overall elimination process.