DRUG DISTRIBUTION

Question 1

What is drug distribution?

Answer 1

Drug distribution refers to the movement of drug to and from the blood and various tissues of the body (for example, fat, muscle, and brain tissue)
and the relative proportions of drug in the tissues.

Question 2

What is the relationship between drug disposition and the plasma concentration?

Answer 2

Disposition is a process that tend to lower the plasma concentration of drug.

Question 3

The two major drug disposition process are

Answer 3

1.Distribution
2. Elimination

Question 4

Factor that affects distribution

Answer 4

1.Blood flow
2. Capillary permeability
3. The degree of binding of the drug to plasma & tissue proteins
4. The relative hydrophobicity of the drug

Question 5

Physiological factors influencing bioavailability of drugs

Answer 5

1. Membrane physiology
2. Age
3. Pregnancy
4. Obesity
5. Diet
6. Disease status

Question 6

How much percentage of total body weight does Interstitial fluid represents ?

Answer 6

Interstitial fluid represents about 15% of the total body weight.

Question 7

How much percentage of total body weight does Intracellular fluid represents ?

Answer 7

Intracellular fluid (fluid inside cells) - 40% of the total body weight.

Question 8

How much percentage of total body weight does blood plasma represents ?

Answer 8

Blood plasma - 8% of the body weight.

Question 9

What does the rate of delivery and potential amount of drug distributed into tissues depends on?

Answer 9

vascular permeability, regional blood flow, cardiac output and perfusion rate of the tissue and the ability of the drug to bind tissue and plasma proteins and its lipid solubility

Question 10

After a drug has entered tissues, drug distribution to the interstitial fluid is determined primarily by

Answer 10

perfusion.

Question 11

What is interstitial fluid?

Answer 11

The interstitial fluid is the fluid that fills the spaces between cells.

Question 12

What is perfusion?

Answer 12

Perfusion is the blood flow at the capillary level in tissue.

Question 13

Four basic processes that explain the disposition of drugs through the body?

Answer 13

absorption, distribution, metabolism, and excretion

Question 14

What is another name of the volume of distribution?

Answer 14

apparent volume of distribution

Question 15

What is volume of distribution?

Answer 15

The volume of distribution (Vd) is a pharmacokinetic parameter representing an individual drug’s propensity to either remain in the plasma or redistribute to other tissue compartments.

Question 16

The equation for Volume of Distribution

Answer 16

Volume of Distribution (L) = Amount of drug in the body (mg) / Plasma concentration of drug (mg/L)

Question 17

A drug with a high Vd has a propensity (tendency) to ?

Answer 17

To leave the plasma and enter the extravascular compartments of the body, meaning that a higher dose of a drug is required to achieve a given plasma concentration.

Question 18

A drug with a low Vd has a propensity to?

Answer 18

remain in the plasma meaning a lower dose of a drug is required to achieve a given plasma concentration

Question 19

A High Vd means

Answer 19

More distribution to other tissue.

Question 20

A low Vd means

Answer 20

Less distribution to other tissue.

Question 21

When does a drug become bound to plasma proteins?

Answer 21

Once a drug has been absorbed into the circulation it may become attached (we say bound) to plasma proteins.

Question 22

What is protein binding like in drug distribution?

Answer 22

However this binding is rapidly reversible and non-specific – that is many drugs may bind to the same protein

Question 23

What is a free form drug?

Answer 23

This is an unencapsulated drug that is not bound to plasma or tissue proteins.

Question 24

What is a bound drug?

Answer 24

This is a drug that is inactive and may act as reservoir.

Question 25

What is the purpose of free drugs?

Answer 25

The free drug distributes from the vasculature into the organ or tissues or may be metabolised and eliminated.

Question 26

What type of process is drug distribution?

Answer 26

It is a passive process whose driving force is the concentration gradient between blood and Extra- vascular tissues.

Question 27

In simple terms what is drug distribution?

Answer 27

In simpler terms, it is reversible transfer of a drug between the blood and the extra vascular fluids and tissues.