Drug Distribution

Question 1

Where does a drug have to go to be active?

Answer 1

Inter or Intracellular spaces.

Question 2

What is drug distribution?

Answer 2

Reversible transfer of a drug between the blood and extravascular fluids and tissues.

Question 3

What are the 6 tissue distributions?

Answer 3

Plasma protein binding
Tissue perfusion
Membrane characteristics
Transport mechanisms
Disease
Elimination

Question 4

Only bound/unbound drug is biologically active.

Answer 4

Unbound

Question 5

Is binding reversible?

Answer 5

Yes

Question 6

What are 5 factors which can affect amount of bound drug?

Answer 6

Renal failure
Hypoalbuminaemia
Pregnancy
Other drugs
Saturability

Question 7

Define apparent volume of distribution (Vd)

Answer 7

Volume in which the amount of drug would be uniformly distributed to produce the observed blood concentration.

Question 8

The greater the Vd, the ______ the ability of the drug to diffuse into and through membranes.

Answer 8

Greater

Question 9

In theory, what should the Vd be?

Answer 9

42L

Question 10

Define clearance.

Answer 10

Theoretical volume of fluid from which a drug is completely removed over a period of time.

Question 11

In renal clearance, what is clearance dependent on?

Answer 11

Concentration

Urine flow rate

Question 12

In hepatic clearance, what is clearance dependent on?

Answer 12

Metabolism

Biliary excretion

Question 13

Define half life.

Answer 13

Time taken for the drug concentration in the blood to decline to half of the current value.

Question 14

What does half life depend on?

Answer 14

Volume of distribution

Rate of clearance

Question 15

Prolongation of the half life will ______ the toxicity of a drug.

Answer 15

Increase

Question 16

To have a therapeutic benefit most drugs need to be given ______.

Answer 16

Chronically.

Question 17

Define drug elimination.

Answer 17

Removal of active drug and metabolites from the body.

Question 18

What are the primary organs for drug excretion?

Answer 18

Kidney

Question 19

What are the 3 principal mechanisms of excretion?

Answer 19

Glomerular Filtration
Passive tubular reabsorption
Active tubular secretion

Question 20

How many litres of fluid does the glomerulus filter per day?

Answer 20

190

Question 21

Where are some drugs actively secreted?

Answer 21

Into the proximal tubule.

Question 22

As filtrate moves down the renal tubule any drug present is ______.

Answer 22

Concentrated

Question 23

Passive diffusion occurs in the ______ tubule.

Answer 23

Distal

Question 24

The liver secrets _ litre of bile a day.

Answer 24

1

Question 25

Biliary secretion accounts for -% of drug elimination.

Answer 25

5-95

Question 26

Define entero-hepatic circulation.

Answer 26

Many drugs are reabsorbed from the bile into the circulation.

Question 27

Metabolism in the liver often leads to ______ of the drug.

Answer 27

Conjugation