Drug distribution

Question 1

What happens once a drug has been absorbed

Answer 1

must be available for biological action and distribution to the tissues

Question 2

Define drug distribution

Answer 2

Transfer of a Drug between the Blood and the Extra Vascular Fluids and Tissues of the body activating the drug

Question 3

What kind of drug is biologically active

Answer 3

an unbound drug

Question 4

What is Tmax and Cmax

Answer 4

The time to maximum plasma concentration (Tmax)

maxiumum plasma concentration (Cmax)

Question 5

The area under the drug concentration-time curve represents

Answer 5

the amount of drug which reaches the systemic circulation and is available for action

Question 6

The bioavailability of a drug is dependant on

Answer 6

extent of absorption and first pass metabolism

Question 7

Drugs binding to proteins in the plasma can be affected by

Answer 7

Renal failure
Hypoalbuminaemia (Low plasma proteins)
Pregnancy
Other drugs
Saturability of binding

Question 8

The less bound a drug is to plasma protein increases its ability to

Answer 8

cross the cell membrane and be activated

Question 9

When is plasma protein binding matter

Answer 9

when binding is above 90%
because if unbound level changes above 90% there is a massive proportional increase in the amount of free drug
also important when tissue distribution is small

Question 10

Volume Of Distribution

Answer 10

overall distribution of drug within the body observed in blood concentrations

Question 11

The greater volume distribution increases the time of what

Answer 11

clearance

Question 12

Define clearance

Answer 12

the theoretical volume of fluid from which a drug is completely removed over a period of time - basic measure of elimination

Question 13

What is clearance dependant on

Answer 13

concentration
Urine flow rate
metabolism
biliary excretion for hepatic clearance.

Question 14

What organs help clearance

Answer 14

Liver
Kidney
maybe gut

Question 15

If liver and kidneys not working what is the result

Answer 15

accumulated drug resulting in toxicity

Question 16

Define the half life

Answer 16

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

Question 17

What is half life dependant on

Answer 17

volume of distribution and rate of clearance

Question 18

If half life of drug prolonged and medicine is continued this increases the volume distribution leading to

Answer 18

toxicity

Question 19

What do we need to know to work out how often a drug can be administrated

Answer 19

half life

Question 20

Define Drug elimination

Answer 20

the removal of active drug and matabolites from the body

Question 21

What are the two parts of drug elimination

Answer 21

Drug metabolism

drug elimination

Question 22

What are the primary organs for drug excretion

Answer 22

the kidneys

Question 23

Where are drugs usually metabolised

Answer 23

Liver

Question 24

where will all unbound drugs be filtered at

Answer 24

glomerulus in kidneys as long as they aren’t to big

Question 25

Factors that affect the glomerular filtration rate will reduce

Answer 25

the clearance of the drug

Question 26

what is entero-hepatic circulation

Answer 26

Many drugs are then reabsorbed from the bile into the circulation

Question 27

when does entero-hepatic circulation stop

Answer 27

when drug is metabolised in the liver or excreted by the kidneys

Question 28

where are drugs usually conjugated - i.e. the chemical substances is terminated

Answer 28

the liver

Question 29

Damage to the liver may reduce the rates of conjugation resulting in

Answer 29

reabsorption or an accumulation resulting in toxicity

Question 30

What are the factors that effect drug distribution

Answer 30

Plasma protein binding
Blood flow - tissue mass ratio
Membrane characteristics - blood brain barrier
Transport mechanisms
Diseases and other drugs (esp renal failure, liver disease, obesity)
Elimination

Question 31

where are some drugs selectively accumulated and what can this lead to

Answer 31

kidneys
eye
bone
selective toxicity

Question 32

What is the transfer of drugs to the brain modified by and why

Answer 32

blood brain barrier - as is much less permeable to water-soluble drugs than is the membrane between plasma and other tissues

Question 33

what does the duration and intensity of the pharmacological effect depend mostly on

Answer 33

renal function