Distribution

Question 1

Name 3 locations where drugs may distribute through the bloodstream?

Answer 1

site of action, site of storage and site of elimination

Question 2

in relation to absorption when does distribution begin?

Answer 2

before absorption is finished

Question 3

what is one thing to consider when dealing with knowing the quanty that enters the body and the actual result?

Answer 3

Most drugs distribute throughout the body, and goes where it is not needed. Thus only a small fraction reaches the receptor sites.

Question 4

what is the tissue order in which the drug distributes through the body (ie where does it act first)

Answer 4

1. plasma, 2. extracellular tissue fluids, 3. cells. Only a small fraction of each dose reaches the target receptor sites.

Question 5

what are the 3 factors that affect the drug distribution in the body?

Answer 5

1. physicochemical properties
2. Anatomy and physiology of patient
3. plasma protein binding.

Question 6

give an example of physicochemical properties, that effect the drug distribution

Answer 6

lipid solubility, degree or ionization or size and molecular weight of the drug

Question 7

what are two examples of anatomy and physiology of patients that may effect drug distribution.

Answer 7

1. tissue perfusion (where organs with higher blood flow get more drugs, less-well-purfused tissues absorb the majority of the drug.)
2. BBB (blood brain barrier)- its impermeable to plasma proteins, and water soluble substances will only enter slowly

Question 8

give an example of a plasma protein that effects the distribution of drugs.

Answer 8

mainly albumin!
its the major carrier of weak acids. protein-bound fraction of drug cannot enter tissues, cannot be eliminated via kidneys, an inert pool of circulating drug.

Question 9

what is volume of distribution and how is it calculated?

Answer 9

its a method to estimate how widely a drug distributes throughout the body. its useful for calculating loading dose of a drug needed to achiece a specific plasma drug level. Its calculated by dividing the amount of drug in the body, by the plasma drug concentration

Question 10

what is the relationship of body volume to body weight?

Answer 10

BV is 1 L/kg of BW

Question 11

what happens when the Vd is >1 L/Kg of BW?

Answer 11

this indicates that the preferential distribution is to the tissues other than blood.

Question 12

what are some distribution properties of water-soluble drugs?

Answer 12

1. tend to have small to intermediate Vd values
2. Distributes well in blood plasma
3. distributes well in the interstitial fluid
4. does not enter intracellular fluids

Question 13

what are some distribution properties of lipid soluble drugs?

Answer 13

1. tend to have high Vd Values

2. distributes into cell membranes, enter cells and distributes well into the brain and adipose