Which expression correctly represents tissue concentration at equilibrium given arterial input Ca, venous concentration Cv, tissue volume Vt, and partition coefficient Kp?

Which expression correctly represents tissue concentration at equilibrium given arterial input Ca, venous concentration Cv, tissue volume Vt, and partition coefficient Kp?

• A. Artery: Ca; Tissue: Vt Ct; Vein: Cv.
• B. Artery: Ca; Tissue: Vt * Kp * Cv; Vein: Cv.
• C. Artery: Cv; Tissue: Vt * Kp * Ca; Vein: Ca.
• D. Artery: Ca; Tissue: Ct; Vein: Cv.

Answer: (B)

Tissue distribution at equilibrium is governed by the tissue–plasma partition coefficient Kp, which links tissue concentration to the blood concentration that equilibrates with the tissue. At equilibrium, the tissue concentration relates to the blood concentration inside the tissue as Ct = Kp × Cv, where Cv is the venous blood concentration leaving the tissue. The amount of drug in the tissue is this concentration times the tissue’s volume, so Amount_tissue = Vt × Ct = Vt × Kp × Cv. The arterial input Ca describes what enters the tissue, but once equilibrium is reached, the final tissue concentration depends on Cv through the partition coefficient. The other forms don’t express Ct in terms of Cv and Kp or mix Ca improperly with tissue concentration.

Tissue distribution at equilibrium is governed by the tissue–plasma partition coefficient Kp, which links tissue concentration to the blood concentration that equilibrates with the tissue. At equilibrium, the tissue concentration relates to the blood concentration inside the tissue as Ct = Kp × Cv, where Cv is the venous blood concentration leaving the tissue. The amount of drug in the tissue is this concentration times the tissue’s volume, so Amount_tissue = Vt × Ct = Vt × Kp × Cv. The arterial input Ca describes what enters the tissue, but once equilibrium is reached, the final tissue concentration depends on Cv through the partition coefficient. The other forms don’t express Ct in terms of Cv and Kp or mix Ca improperly with tissue concentration.