Drug Distribution

Question 1

What amount of body weight does total body water make up?

Answer 1

60%

Question 2

What amount of body weight does intracellular fluid make up?

Answer 2

40%

Question 3

What amount of body weight does extracellular fluid make up?

Answer 3

20%

Question 4

What amount of body weight does plasma fluid make up?

Answer 4

4%

Question 5

What amount of body weight does blood volume take up?

Answer 5

7%

Question 6

Is the plasma concentration the same as the blood concentration when it comes to drug distribution, or different? What assumptions are you making here?

Answer 6

• It is the same!

- You are assuming that the drug is excluded from the RBCs, and that the drug does not cross the membrane of the RBCs

Question 7

Following absorption the pattern of drug distribution is covered by what?

Answer 7

the rate of blood flow (perfusion) to each tissue and the affinity of the drug to accumulate in the tissue

Question 8

Tissues that receive the highest blood flow will rapidly _____, while tissues that receive the lowest flow will do it slower

Answer 8

equilabrate with the drug

Question 9

Blood flow is an important factor in determining the _____ of drugs

Answer 9

initial distribution

Question 10

Drug accumulation into tissues is dependent upon both ______ and _______ for the drug

Answer 10

Blood flow

Tissue affinity

Question 11

Drugs with high tissue affinity tend to accumulate and concentration in the ____

Answer 11

tissue (these will remain in the tissue long after it is depleted in plasma)

Question 12

Tissue concentration of drugs with low tissue affinity will do what?

Answer 12

equilibrate rapidly with the plasma drug concentration and decline rapidly as the drug is eliminated from the plasma

Question 13

Highly lipophilic drugs are extracted by poorly ______ organs, hence drug accumulation is slow. Removal from fat tissue for these drugs is also slow

Answer 13

perfused

Question 14

What is the formula for volume of distribution?

Answer 14

Volume = amount of drug added (mg) / drug concentration (mg/L)

Question 15

Why does the AAG go up, but the albumin go down in renal failure?

Answer 15

• in renal failure, the kidney becomes leaky and by becoming leaky you get leakage of the protein (you pee out the protein from the body) - the albumin levels are reduced, you need to look at what is going on in the individual and adjust the dose

Question 16

Why does the concentration of albumin decrease in patients with cirrhosis?

Answer 16

• in cirrhosis, there is a fibrous build up in the membranes of the liver, and the liver is VERY tough. There is no exchange in drug uptake or protein uptake. Albumin is made in the liver, so if the liver is damaged or failing it is not excreting the albumin protein anymore. Long term effects of cirrhosis is that the albumin concentrations are decreasing

Question 17

Why does the albumin levels go down in people that are severely burned?

Answer 17

• in burns, you have no skin, so in the fluid that is leaking from the skin you will have a lot of albumin that is leached out - you are loosing a lot of that protein

Question 18

Why is the albumin levels decreased in pregnancy?

Answer 18

• the albumin concentration goes down because there are 2 different circulations that need to be worried about

Question 19

When does a 5% change in protein binding matter?

Answer 19

• In highly protein bound drugs - have to worry about a change in protein binding
• Not as highly protein bound - do not have to worry about a 5% change as much

Question 20

Is phenytoin protein bound or not?

Answer 20

yes, it is protein bound