Which factor increases fat-soluble drug distribution in obesity?

Which factor increases fat-soluble drug distribution in obesity?

• A. Increased skeletal muscle mass
• B. Higher plasma protein binding
• C. Faster hepatic metabolism
• D. Increased adipose tissue relative to lean body mass

Answer: (D)

In obesity, fat mass is increased, and fat-soluble drugs readily partition into adipose tissue. This expands the amount of drug that resides outside the plasma, raising the volume of distribution and often prolonging the drug’s effect because a larger reservoir is available to release the drug over time. The other factors don’t produce this effect: more skeletal muscle mass mainly affects distribution for water-soluble drugs; higher plasma protein binding traps more drug in the bloodstream and reduces tissue distribution; and faster hepatic metabolism changes clearance rather than where the drug distributes. Increased adipose tissue relative to lean body mass directly provides a larger reservoir for lipophilic drugs, making distribution greater.

In obesity, fat mass is increased, and fat-soluble drugs readily partition into adipose tissue. This expands the amount of drug that resides outside the plasma, raising the volume of distribution and often prolonging the drug’s effect because a larger reservoir is available to release the drug over time. The other factors don’t produce this effect: more skeletal muscle mass mainly affects distribution for water-soluble drugs; higher plasma protein binding traps more drug in the bloodstream and reduces tissue distribution; and faster hepatic metabolism changes clearance rather than where the drug distributes. Increased adipose tissue relative to lean body mass directly provides a larger reservoir for lipophilic drugs, making distribution greater.