Sun28November0440PM 23

Which of the following best explains why phenytoin has a low hepatic extraction ratio?

(Please select 1 option)

It has a clearance that is insensitive to changes in liver blood flow This is the correct answer

It has a clearance that is insensitive to changes in drug metabolism

It has an extensive first pass metabolism when given orally

It has a clearance that is insensitive to changes in drug excretion Incorrect answer selected

It has a clearance that is insensitive to changes in binding to plasma proteins

Explanation

Drugs with a low hepatic extraction ratio have the following pharmacokinetic properties:

Drug clearance is insensitive to changes of liver blood flow

Drug clearance is very sensitive to alterations in protein binding, intrinsic metabolism and excretion, and

Have no first pass metabolism when given orally.

Examples of drugs with low hepatic extraction ratios include warfarin and phenytoin.

Drugs with a high hepatic extraction ratio have the following pharmacokinetic properties:

Undergo extensive first pass metabolism when given orally

Drug clearance that is dependent on liver blood flow, and

Drug clearance is less sensitive to alterations in protein binding and intrinsic metabolism.

Examples of drugs with high hepatic extraction ratios include morphine, lidocaine, propranolol and etomidate.

Answer Statistics

1

42%

2

16%

3

15%

4

8%

5

21%

Times answered: 239