Higher tissue affinity for a drug results in what change to the drug's distribution?

Higher tissue affinity for a drug results in what change to the drug's distribution?

• A. Lower volume of distribution
• B. Higher plasma concentration and lower VD
• C. Lower plasma concentration and higher volume of distribution
• D. Higher plasma concentration and higher VD

Answer: (C)

When a drug has a high affinity for tissues, more of the drug leaves the bloodstream and accumulates in tissues. The volume of distribution (VD) is a calculated measure: VD = amount of drug in the body divided by the plasma concentration. With more drug in tissues for the same dose, the plasma concentration drops, while the amount in the body remains the same, causing VD to increase. So higher tissue affinity leads to a lower plasma concentration and a higher volume of distribution. This pattern contrasts with a scenario where the drug largely stays in the plasma, which would yield a lower VD and a higher plasma concentration.

When a drug has a high affinity for tissues, more of the drug leaves the bloodstream and accumulates in tissues. The volume of distribution (VD) is a calculated measure: VD = amount of drug in the body divided by the plasma concentration. With more drug in tissues for the same dose, the plasma concentration drops, while the amount in the body remains the same, causing VD to increase. So higher tissue affinity leads to a lower plasma concentration and a higher volume of distribution.

This pattern contrasts with a scenario where the drug largely stays in the plasma, which would yield a lower VD and a higher plasma concentration.