If a drug has a Kp value greater than 1 for a given tissue, what does this imply about tissue distribution?

If a drug has a Kp value greater than 1 for a given tissue, what does this imply about tissue distribution?

• A. The tissue concentration is lower than plasma
• B. The tissue concentration is higher than plasma
• C. Equilibrium cannot be reached
• D. The drug is rapidly cleared from tissue

Answer: (B)

Kp is the tissue/plasma partition coefficient, defined as the ratio of the drug concentration in tissue to that in plasma at steady state. If this ratio is greater than one, the tissue concentration ends up higher than the plasma concentration, meaning the drug preferentially distributes into that tissue and can accumulate there. This reflects factors like the drug’s lipophilicity, tissue binding, and sequestration within the tissue compartments. In contrast, a Kp less than one would indicate the tissue concentration is lower than plasma, and a Kp of about one suggests similar levels in both compartments.

Kp is the tissue/plasma partition coefficient, defined as the ratio of the drug concentration in tissue to that in plasma at steady state. If this ratio is greater than one, the tissue concentration ends up higher than the plasma concentration, meaning the drug preferentially distributes into that tissue and can accumulate there. This reflects factors like the drug’s lipophilicity, tissue binding, and sequestration within the tissue compartments. In contrast, a Kp less than one would indicate the tissue concentration is lower than plasma, and a Kp of about one suggests similar levels in both compartments.