Increasing plasma protein binding of a drug will primarily influence its volume of distribution by...

Increasing plasma protein binding of a drug will primarily influence its volume of distribution by...

• A. Increasing volume of distribution
• B. Decreasing volume of distribution
• C. No change in volume of distribution
• D. Immediate elimination

Answer: (B)

Increasing plasma protein binding lowers the free fraction of drug that can leave the bloodstream and enter tissues. Volume of distribution reflects how much drug distributes beyond the plasma; when more drug is bound in plasma, less distributes into tissues, so the apparent volume of distribution decreases, pulling it toward the plasma (in extreme cases, toward the plasma volume). Plasma proteins like albumin or alpha-1 acid glycoprotein act as reservoirs, keeping more drug in the blood and limiting tissue distribution. This change does not imply immediate elimination; clearance is a separate concept tied to the unbound fraction, but distribution is reduced with higher binding.

Increasing plasma protein binding lowers the free fraction of drug that can leave the bloodstream and enter tissues. Volume of distribution reflects how much drug distributes beyond the plasma; when more drug is bound in plasma, less distributes into tissues, so the apparent volume of distribution decreases, pulling it toward the plasma (in extreme cases, toward the plasma volume). Plasma proteins like albumin or alpha-1 acid glycoprotein act as reservoirs, keeping more drug in the blood and limiting tissue distribution. This change does not imply immediate elimination; clearance is a separate concept tied to the unbound fraction, but distribution is reduced with higher binding.