Clinical Pharmacokinetics II

Question 1

Define hepatic extraction ratio:

Answer 1

The fraction of a drug extracted by the liver in first pass metabolism

Question 2

Relationship of bioavailability and hep. extr. ratio

Answer 2

Bioavailability = 1-Extraction Ratio

Question 3

Bioavailability of an IV drug

Answer 3

1

Question 4

Changing hepatic activity will have a low effect on a drug with a _______ Eh

Answer 4

low

Question 5

Changing hepatic activity will have a high effect on a drug with a _______ Eh

Answer 5

High

Question 6

What does it mean to say two drugs are bioequivalent

Answer 6

The extent and rate of absorption of the drug are so similar that there is likely no clinically important difference between their effects

Question 7

If 100% of drug is absorbed through gut, how to calculate bioequiv?

Answer 7

F=1-Eh

Question 8

Mathematical requirements for bioequivalence

Answer 8

90% confidence interval of the AUC ratio between 0.8 and 1.25

Question 9

Only unbound drug is ______

Answer 9

active

Question 10

Other than the target tissue, where else may the drug distribute

Answer 10

Fat
Other tissues
plasma proteins

Question 11

What drugs tend to be excluded by cell membranes

Answer 11

Very polar drug molecules

Question 12

What drugs tend to be confined to circulation

Answer 12

Very large ones

Question 13

What is Vd

Answer 13

The constant relating the amount of drug in the body to the plasma drug concentration

Question 14

Equation for Vd

Answer 14

(total amount of drug in the body)/Plasma drug concentration

Question 15

Give an example of a situation with a very low apparent volume distribution

Answer 15

High amounts of a substance are protein bound in the plasma

Question 16

Give an example of a situation with a very high apparent volume distribution

Answer 16

drugs absorbed and retained in the fat cells, leaving very little in the plasma

Question 17

Influence of dose on Vd? Concentration?

Answer 17

None

Vd is a constant

Question 18

What does steady state mean?

Answer 18

The condition in which the average total amount of drug in the body remains stable over time of dosing
(input=elimination)

Question 19

What is a maintenance dose rate

Answer 19

Mass/Time of drug input to maintain the drug concentration in steady state

Question 20

What do you provide to give an initial appropriate drug level before maintenance doses?

Answer 20

Loading Doses

Question 21

Loading dose equation

Answer 21

(Vd)(target plasma conc)

Question 22

What is metabolism?

Answer 22

The irreversible transformation of parent compounds into daughter compounds

Question 23

Metabolism diminishes drug activity in what two ways

Answer 23

Inactivation and Elimination

Question 24

How are most drugs excreted?

Answer 24

Via the kidney

Question 25

Define Clearance

Answer 25

• The efficiency that the drug (vol) is irreversibly eliminated from the volume of distribution
• Final value should be vol/time

Question 26

Define Elimination Rate

Answer 26

The amount of the drug (mass) that is irreversibly eliminated form the dose per unit time

Question 27

Elimination Rate Equation

Answer 27

ER = (Clearance)*(Plasma Concentration)

Question 28

Define Elimination Rate Constant

Answer 28

The fraction of the drug volume that is irreversibly eliminated from the volume of distribution per unit time

Question 29

Elimination Rate Constant Equation

Answer 29

K = Clearance/Volume of Distribution

ex. 20% of drug/hour

Question 30

Increasing the plasma concentration of a drug will ______ its ER

Answer 30

Increase it

ER=CL(Cp)

Question 31

At steady state, Maintenance dose rate =

Answer 31

Elimination Rate

Question 32

Maintenance dose rate equation =

Answer 32

(Clearance) (Steady state drug Conc)

Question 33

Equation for organ clearance

Answer 33

CL= Organ Extraction Ration (Organ Blood Flow)